Problem/symptoms:
When I left for work this morning, I noticed my bike was running a bit rough. As I brought the bike to a stop sign I had to keep giving it gas to keep from dying. I turned onto the main road and instantly realized my bike couldn't deliver power; so I turned around to limp home. It was difficult to go over 40mph. Since I had just done some work on the bike I thought it was as easy as an oversight or bad part, but after some initial testing I'm concerned it may be far worse.

Recent work done:
- After running 2 tanks with Seafoam, I removed my carbs for a good cleaning, which included soaking main and pilot jets in B-12 chemtool.
- Then I decided to change the main from #98 to #100, since I had planned to do this anyways.
- I replaced the right coil with a new one from ebay.


Reason for work:
Cleaning carbs: Since my bike is a commuter I've never had to worry about my carbs gumming up from sitting dormant. But after sitting in pieces for two weeks while I redid my steering bearings (longest time it's ever gone without being used), something felt funny when I returned to the road.
I described the problem in another thread like this: "I'm having an intermittent issue. My first assumption is that my jets may have started to clog, since I haven't done recent engine work....... For the most part everything seems normal, but sometimes when I roll on the throttle aggressively (1/2 to 3/4 throttle) before the RPM gets close too the rev limiter (guessing @ 8-10 RPM maybe) it feels like it cuts out. It doesn't feel like a lean surge, and I don't THINK it feels like a rich bogging... it's difficult to describe. Almost like it sputters and looses all power, but only a second."
For reference: http://www.ninjette.org/forums/showthread.php?p=817615#post817615 My description was comment #15.
The general consensus was that I COULD have started to gum up, but even more likely that I had moisture in the fuel.

Changing main jet: My never-ending quest to find jetting perfection.

Replacing right coil: The original coil wire broke when I removed it to read my plugs.

Trouble-shooting:
- Thinking I either got a bum replacement coil, or installed it improperly, I double-checked my work. It was good.
- I verified the coil worked by sparking the plug against the case (right and left). Both sides worked.
- Then I did a compression test with the following results (on a cold engine):
left = 165 psi
right = 125 psi (155 wet)
Service manual states the usable range is 142~218 psi OR 139~213 psi. One of these must have been a mistake in the manual.
- Checked oil sight glass for coolant contamination. None detected.


I don't know what to do now. What are my options?

You need a minimum of 125 to get anything. I would find a machine shop and pull the headm . Then while they have the head replace the pistons and rings. Have the machine shop hone the cylinder block. Get a new chain tentioner also. But photo everything as it comes apart before spending money

You need a minimum of 125 to get anything. I would find a machine shop and pull the headm . Then while they have the head replace the pistons and rings. Have the machine shop hone the cylinder block. Get a new chain tentioner also. But photo everything as it comes apart before spending money


Ballpark, what would that run me? Is it more cost effective to order another ebay engine? This was my 2nd.

Do they things really just go bad all of a sudden?

I've got a manual tensioner, so that part is covered.

When machines fail it always interest me. No idea what straw break the cammels back.
As for cost. I don't know. Couple hundred for labor o would guess. E bay engines are good at this point. But you don't know the history.

Are you sure the spark plug still good? If the fire seems unfocused, moving around between electrode instead of shape similar on each spark, its time to replace.

Are you sure the spark plug still good? If the fire seems unfocused, moving around between electrode instead of shape similar on each spark, its time to replace.

I thought about trying a new plug for a moment too, but I don't see how this would effect the compression, as the test is done without plugs. I just double-checked the battery, which read 12.84v at the battery (off). The difference between dry and wet tests also suggests to me their isn't a great seal inside the cylinder. I don't have a ton of experience, but picked this stuff up from the last time I killed an engine. My current engine is from ebay.

My bike was once at the state of low compression. The valves got clogged with carbon deposit. It was really hard to start the engine, had to push start. But that was due to bad quality fuel in my country, RON 88 subsidized fuel. It lacks of detergent chemicals that was usually mixed into more expensive fuel.

My bike was once at the state of low compression. The valves got clogged with carbon deposit. It was really hard to start the engine, had to push start. But that was due to bad quality fuel in my country, RON 88 subsidized fuel. It lacks of detergent chemicals that was usually mixed into more expensive fuel.

That's something to think about. I've been taking the long road to re-jetting, as I use it daily, and can't always take the time to tinker on non-essentials, so I know there are times I've gone for a while with both lean and really rich spots. Plugs are black, but not fouled or REALLY black. All that to say I'm sure I'm likely not burning all my fuel. Can I reasonable check this out in my garage? I'd have to buy more tools, huh?

That's something to think about. I've been taking the long road to re-jetting, as I use it daily, and can't always take the time to tinker on non-essentials, so I know there are times I've gone for a while with both lean and really rich spots. Plugs are black, but not fouled or REALLY black. All that to say I'm sure I'm likely not burning all my fuel. Can I reasonable check this out in my garage? I'd have to buy more tools, huh?

I also never did the cleaning my self, but i did help my mechanic pal working on my bikes. You should get ratchet socket wrench set. And long T socket wrench set to ease you remove the cylinder head. He opened the valve keeper by putting suitable sized socket bit on top of spring seat and hit it with hummer. Flexible cable grinder to reseat the valve, and valve reseating grease. Sandpaper to clean up the valve surface and cylinder surface. Find TDC first on the right cylinder before start working with your bike.

When you had the plus out to do the compression check, was one spark plug appreciabably darker/sootier than the other?

When it's running, is one exhaust header cooler than the other (via touch or infrared thermometer)?

Are the valve rocker clearances consistent on both cylinders?
(Would the "carbon buildup on the valves" cause valve clearance to be a bit greater? I dunno...)

I'd consider those easy, relatively non-invasive checks before doing the more drastic stuff.

check spark on the new coil

When you had the plus out to do the compression check, was one spark plug appreciabably darker/sootier than the other?

When it's running, is one exhaust header cooler than the other (via touch or infrared thermometer)?

Are the valve rocker clearances consistent on both cylinders?
(Would the "carbon buildup on the valves" cause valve clearance to be a bit greater? I dunno...)

I'd consider those easy, relatively non-invasive checks before doing the more drastic stuff.

They were about the same.
I didn't think about checking temp on each side before removing the tank.
I'd have to check the clearances, but I do those myself, and the next scheduled adjustment is in a couple-few thousand miles. I rarely see much variation though.

check spark on the new coil

Yes, it sparks against the case (both sides do). This still wouldn't explain super low compression results though.

They were about the same.
I didn't think about checking temp on each side before removing the tank.
I'd have to check the clearances, but I do those myself, and the next scheduled adjustment is in a couple-few thousand miles. I rarely see much variation though.

I'm with dcj - check all of the simple stuff before digging in.

Check the valves and look for any odd measurements. If you have been using a fuel system cleaner it's possible that you dislodged some carbon and it's holding the valve open slightly - like silent suggested.

it's not hard to pull the head off and examine the valves and piston rings.

it's not hard to pull the head off and examine the valves and piston rings.

Understood. But it takes time and gaskets and is somewhat invasive.

I'm a lazy guy (economical with my effort?) and prefer trying a few easy things before tearing into carbs, heads, or the guts of an engine. And the less I have to dismantle, the less I can screw up.

I'm a lazy guy


i hear ya

Understood. But it takes time and gaskets and is somewhat invasive.

I'm a lazy guy (economical with my effort?) and prefer trying a few easy things before tearing into carbs, heads, or the guts of an engine. And the less I have to dismantle, the less I can screw up.

I fully agree with Dave.

The origin of the problem is almost always caused by the last work we did, directly or indirectly.

The more you dig, the more problems you may create, having a really mess very soon.

Compression has been bad for long time, unless you couldn't measure it properly, a head gasket suddenly failed or a valve suddenly remains semi-open.

The missing explosions needs to be identified; left or right cylinder.

The missing ingredient of the explosions needs to be identified:

Fuel: You could drain bowls and re-check.

Heat: You could switch coils and re-check.

Seeing a spark means nothing, sparks may be absent when the electrodes are feeling the high pressure of the compression.

The new variable in the equation is the new coil: it will be guilty until absolutely proved innocent. :)

Putting the gas tank back on and hooking it up should only take a few minutes. Then run it and try the things Hernan suggests.

I'm with dcj - check all of the simple stuff before digging in.

Check the valves and look for any odd measurements. If you have been using a fuel system cleaner it's possible that you dislodged some carbon and it's holding the valve open slightly - like silent suggested.

That's brilliant! I'll investigate further.

I fully agree with Dave.

The origin of the problem is almost always caused by the last work we did, directly or indirectly.

The more you dig, the more problems you may create, having a really mess very soon.

Compression has been bad for long time, unless you couldn't measure it properly, a head gasket suddenly failed or a valve suddenly remains semi-open.

The missing explosions needs to be identified; left or right cylinder.

The missing ingredient of the explosions needs to be identified:

Fuel: You could drain bowls and re-check.

Heat: You could switch coils and re-check.

Seeing a spark means nothing, sparks may be absent when the electrodes are feeling the high pressure of the compression.

The new variable in the equation is the new coil: it will be guilty until absolutely proved innocent. :)

Agreed. I'll also be following-up on this.
It's been a $hity day, so now it's time for burbon and bed.

A couple questions I work up with this morning since all this has been running through my mind:

1) Does it appear likely that the symptoms I mentioned BEFORE I cleaned the carbs are relevant or related to the dead/weak cylinder (other than the carbon and valve theory)? I'm referring to it temporarily cutting out or sputtering mid-throttle.

2) Would a WET compression test temporarily seal the valves in the same way it does bad rings?

1) Yes, but only if the symptoms appeared immediately after the clean up.

2) No.
More oil than the minimum necessary to seal the rings (a few drops) may damage the engine and give a false compression reading.
At top dead center (TDC) position of the crackshaft, each combustion's chamber has only around 10 cc or 0.34 oz of volume.

1) Yes, but only if the symptoms appeared immediately after the clean up.



This symptom started after siting for 2 weeks while I replaced the steering bearings, and was the reason for the clean-up 2 tanks later. So I guess it was technically already there.

I don't have much to report yet, as I've had to focus on other aspects of life, but prepped the bike to measure valve clearances.

I just discovered a reasonably priced Valve Spring Compressor tool (Tusk), so I may be up for tackling a new level, if need be. Would I need a case separator too, or can I pull the engine apart without it?

It's been a while, but I just measured the valve clearances. As I understand from our discussion, I was hoping for the bad cylinder to be way out of spec., as this could explain the poor compression. Well, 3 of 4 valves on the bad side was exactly in spec, and the other was out but technically within spec. limits. So I guess in this case it's bad news.

Clearances are as follows:

- Left (good compression) cylinder
(Exhaust) = .010"/.254mm & .009"/.229mm
(intake) = .007"/.178mm & .008"/.203mm

-Right (poor compression) cylinder
(Exhaust) = .010"/.254mm & .010"/.254mm
(intake) = .008"/.203mm & .007"/.178mm

Have we determined the rings are now the most likely cause of poor compression?

Removing the head and cylinder block is easy. We can walk you through it.

What brand compression tool tester are you using? Some brands are better than others. Do you know anyone with another brand to get a second verification?

It's late and I have to be at work in a few hours.

Is it possible to swap the coils?
and did you try to buy brand new spark plugs?

The compression tester is from Harbor Freight. It's results have been consistent.

I do have new plugs. I have the original coils and the eBay one. The eBay one is the one I used when I discovered I lost a side. That being said, this was also before I realized my first coil wasn't really broken, but the wire just screws back in. I have that one back on now, but this is also the point I checked compression before proceeding further.

Which wire are you referring to?

I guess it is not the ring (if you refer to the piston ring). If it was, the exhaust smoke should turn white, more white than smoke comes from healthy 2 stroke engine.I still guess carbon deposit sits between the valve and the valve seat (intake and exhaust mouth).

Unfortunately I dont know any cheap method to test which valve is leaking without taking off the head. If you are willing to take off the head, you can test it by pouring gasoline/water on the cylinder dome, while the head is upside down.

Or if you could somehow inject compressed air through the spark hole, without leaking back, you should be able to feel it whether it's the intake or the exhaust valve.

Which wire are you referring to?

The spark-plug wire.

I guess it is not the ring (if you refer to the piston ring). If it was, the exhaust smoke should turn white, more white than smoke comes from healthy 2 stroke engine.I still guess carbon deposit sits between the valve and the valve seat (intake and exhaust mouth).

Unfortunately I dont know any cheap method to test which valve is leaking without taking off the head. If you are willing to take off the head, you can test it by pouring gasoline/water on the cylinder dome, while the head is upside down.

Or if you could somehow inject compressed air through the spark hole, without leaking back, you should be able to feel it whether it's the intake or the exhaust valve.

I can believe that. I suspect I was lean down low, but rich up mid to high.
I have an air compressor, and a tire valve remover. If I remove the valve from the compression tester hose, to allow air to be forced the opposite direction, and connect the air compressor to that, would that serve as my ghetto leak-down tester? I did try the homeless man's version of leak-down testing by cranking it by hand and listening, but that wasn't very effective.

If my compressor idea might work, at what point do I turn the engine over to to seal the valves? Am I good as long as none of the cam lobes are compressing the buckets? I'm also assuming I'd want the cylinder at the bottom to give the most surface area possible to test... unless we're not isolating valves, but isolating which valve?

All that being said, I am willing, and am psychologically preparing myself to split the case if recommended. Since my problems started, I have since acquired a big(baby) brother for my little Ninjette, so I don't have the same urgency for transportation, and can take my time to do it right. If the recommendation is to start removing the engine to proceed with major surgery, will I need to purchase a case-splitter, or is the head easily removed without? Will I need a new gasket, or is it reusable like the valve cover gasket is?

I really appreciate your help guys. I was ready to give up and start parting it out, but am excited about learning/gaining a new level of experience, and getting her running again. Funds are tight, so depending on parts and tools, it may have a delay or two. In case I haven't mentioned it, remember I do have the original engine as a parts engine. Although I don't remember the numbers, the compression was poor on that engine, but this one is better on one side, and much worse on the other.

I had exactly this and it was just an ht lead working its way out of the coil. It would spark open but obviously not under compression. Check that easy glitch first and snug it all up. Since you just changed a coil its a favorite.

I can believe that. I suspect I was lean down low, but rich up mid to high.
I have an air compressor, and a tire valve remover. If I remove the valve from the compression tester hose, to allow air to be forced the opposite direction, and connect the air compressor to that, would that serve as my ghetto leak-down tester? I did try the homeless man's version of leak-down testing by cranking it by hand and listening, but that wasn't very effective.

If my compressor idea might work, at what point do I turn the engine over to to seal the valves? Am I good as long as none of the cam lobes are compressing the buckets? I'm also assuming I'd want the cylinder at the bottom to give the most surface area possible to test... unless we're not isolating valves, but isolating which valve?

All that being said, I am willing, and am psychologically preparing myself to split the case if recommended. Since my problems started, I have since acquired a big(baby) brother for my little Ninjette, so I don't have the same urgency for transportation, and can take my time to do it right. If the recommendation is to start removing the engine to proceed with major surgery, will I need to purchase a case-splitter, or is the head easily removed without? Will I need a new gasket, or is it reusable like the valve cover gasket is?

I really appreciate your help guys. I was ready to give up and start parting it out, but am excited about learning/gaining a new level of experience, and getting her running again. Funds are tight, so depending on parts and tools, it may have a delay or two. In case I haven't mentioned it, remember I do have the original engine as a parts engine. Although I don't remember the numbers, the compression was poor on that engine, but this one is better on one side, and much worse on the other.

You dont need to remove the engine out of the chassis to remove the head. After you remove all the head bolts, and both camshaft, and tie the camchain to the chassis tube over it, you just have to pull it. It's not glued. May be if it's stuck you can gently hit the edge with flat screwdriver. And take the metal gasket below it for reuse later.

For the tester, why dont you give a try? First you have to make sure the engine at TDC, which is right cylinder on top. Here you can test the right cylinder right away. Feel by hand whether air come through the intake port or exhaust. You can close the port by hand and feel the pressure. If you feel pressure right away as you let pressurized air into cylinder, that may be good indication if it is leaking.

As the engine has 180 crank angle, the left cylinder fires when the right cylinder at BTDC at the end of power stroke. So to find left cylinder TDC, insert a screwdriver through the spark hole of the left. If you follow TDC finding method on the manual, it should be the right cylinder that is at TDC. Then you crank the engine by hand until the screwdriver stop moving up. left cylinder should be at TDC. Then you can test the compression on the left.

Here may be the makeshift compression tester with air compressor looks like
http://forums.g2ic.com/tegtips/engine/30.html

Thanks; you make it sound easy, and not so intimidating.

Thanks; you make it sound easy, and not so intimidating.

Well I just put out the concept. I assume you already drain the coolant and remove the coolant tank, remove all the bodywork and fuel tank, remove the kleen air system, and remove the carb right?

Beside, the step by step guide is already covered in DIY guides over the internet and the workshop manual.

Well I just put out the concept. I assume you already drain the coolant and remove the coolant tank, remove all the bodywork and tank, remove the kleen air system, and remove the carb right?

Beside, the step by step guide is already covered in DIY guide and the workshop manual.

Yes, I haven't reassembled since I checked the valve clearances last night. I haven't removed the carbs yes, but I've done that too many times before.

How did this end up?

How did this end up?

Pending... I'm cleaning up the garage, as I don't have the space I need to work productively. I got tired of stepping over stuff and twisting every time I need a new tool.

Been there. Hope it turns out well.

It's taken me a while to get to this, but I got it apart this evening - I was actually surprised how easy it was.

Here are some select pictures. Do they reveal anything? I 'd be happy to take specific clarifying photos if it would be helpful.


https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11608

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11607

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11606

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11609

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11610

cyl #2 has something going on as that piston is much more carboned up than #1. From your pic of the head, it almost looks like the spark plug hole is now oblong or blown out, but I'm sure that's a camera angle thing. to check, thread the plug back in by hand.

That scratch on your cylinder wall is cause for concern. it would be allowing massive blowby. For reference, is this the cylinder that gave you bad compression readings? If so, bore the cylinder out +2mm and get an oversize kit. Otherwise, find a good cylinder on eBay, light hone it and re-assemble.

That scratch on your cylinder wall is cause for concern. it would be allowing massive blowby.

"massive blowby"? I don't think so, it's just a graze, stop scaring the poor fella with melodramatic exaggeration :)
The scratch is from the middle ring groove, Id check that ring for a broken end or a particle of something in the ring gap. If an end has broken off and you can't see it it might have fallen into the crankcase when you pulled the cylinders, in which case it is puzzle time to retrieve it!
It all looks pretty good
Put the plugs in and flip the head. Pour some gas or white spirit into the combustion chambers (level to the surface) and see if any leaks out past a bad valve seat. If not and I can't see any sign of a blown gasket either, you are back to carbs 80%, an ignition glitch under compression 10%, ( I believe the spark plug air gap is effectively multiplied by compression ratio so an open air test is not fool proof that the whole HT circuit is good ) or a tight valve clearance 10%
But Carbs, it is nearly always carbs!

"massive blowby"? I don't think so, it's just a graze, stop scaring the poor fella with melodramatic exaggeration :)
The scratch is from the middle ring groove, Id check that ring for a broken end or a particle of something in the ring gap. If an end has broken off and you can't see it it might have fallen into the crankcase when you pulled the cylinders, in which case it is puzzle time to retrieve it!
It all looks pretty good
Put the plugs in and flip the head. Pour some gas or white spirit into the combustion chambers (level to the surface) and see if any leaks out past a bad valve seat. If not and I can't see any sign of a blown gasket either, you are back to carbs 80%, an ignition glitch under compression 10%, ( I believe the spark plug air gap is effectively multiplied by compression ratio so an open air test is not fool proof that the whole HT circuit is good ) or a tight valve clearance 10%
But Carbs, it is nearly always carbs!

Upon my first ever reassembly of the ninja 250 motor I rolled 1 of the oil rings. it barely scratched the wall to the point where I could barely see it. I asked a well-known performance shop about this and was told to hone it as I would get blow-by from it. Another member of this board had a similar scratch and actually experienced the blow-by. Again, his scratch barely appeared in photos.

a scratch that deep will bleed compressed gases at a high rate. If a leak-down test was performed, one would see a high percentage of air loss with a scratch like that. A compression test would reveal similar results and guess what? The OP posted the below:

"left = 165 psi
right = 125 psi (155 wet)"

So please, unless you work on motors often, don't tell me that I am melodramatic. Also, "massive" blow-by is relative anyways as I keep my motors tight and have very minimal leak down.

Yes, it sparks against the case (both sides do). This still wouldn't explain super low compression results though.

the scratch in the cylinder, and most likely the bad rings would.

check the play on your crank and rods

1. I work with motors fairly often and have done for 45 years
Apologies if I came across too combative there :o But one thing I have learned over the years is to remain calm with engines and not go into overkill. Agree with Motofool's post of 19th March.:thumbup:

2. I do not believe you will lose 40 psi down that scratch, nor do I believe that it would cause massive blow by and stop the cylinder firing. Come on:)
You could give the bore a light hone if you were worried and wanted perfection, You can still see the factory cross hatching (without seeing all the way round) so it doesn't seem too worn.

3. I am more concerned about what made the scratch and why than the scratch itself. the second ring helps with compression and if it is broken would cause some compression loss along with a bit less oil scraping
Check the valve seats and middle ring gap like I said.
If any full time mechanic on here (we must have one) disagrees with me I'll take it on the chin :cool:

4. One exhaust valve seems to be running hotter than the rest but evenly hotter so maybe a tight tappet, or worse, sticking.

My money is on a broken middle ring, about 4mm off the end, though that is a lucky find and not the cause of running on one cylinder.

check the play on your crank and rods

the mark on the side of the case is machined. as evidenced by the horizontal nature of the cuts. if the piston did it, it would be vertical in the picture and the engine would have made a lot of noise.

If this is not what you were referring to alex, then sorry.

check the play on your crank and rods
A well known cause of poor compression and running on one cylinder :D

1. Agreed

2. Why do you think people do WET tests? something to fill the scratch(es) and voids between the rings and cylinder wall perhaps? Thus bumping the compression number showing cause for concern due to a piston ring issue? Come on yourself man. Notice his WET test bumped 30 psi.

In the end, I think we both agree there is a ring issue.

3. Agreed. Investigation into the cause must be done.


1. I work with motors fairly often and have done for 45 years
Apologies if I came across too combative there :o But one thing I have learned over the years is to remain calm with engines and not go into overkill. Agree with Motofool's post of 19th March.:thumbup:

2. I do not believe you will lose 40 psi down that scratch, nor do I believe that it would cause massive blow by and stop the cylinder firing. Come on:)
You could give the bore a light hone if you were worried and wanted perfection, You can still see the factory cross hatching (without seeing all the way round) so it doesn't seem too worn.

3. I am more concerned about what made the scratch and why than the scratch itself. the second ring helps with compression and if it is broken would cause some compression loss along with a bit less oil scraping
Check the valve seats and middle ring gap like I said.
If any full time mechanic on here (we must have one) disagrees with me I'll take it on the chin :cool:

4. One exhaust valve seems to be running hotter than the rest but evenly hotter so maybe a tight tappet, or worse, sticking.

My money is on a broken middle ring, about 4mm off the end, though that is a lucky find and not the cause of running on one cylinder.

I should go racing to get away from competitive sports like online diagnosis :D

Engines should run down to 100 psi, way below what he has wet or dry, I have had cars run at 70 or 80. I cant see any characteristic dark marks from blow by either,
I definitely think that valve is a clue to the actual loss of that cylinder, it is spending less time on its seat than it should be.

Oddly this motor wont run if it doesn't have 125 psi or better. Both I and Racer x have experienced this.

cyl #2 has something going on as that piston is much more carboned up than #1. .

Is it possible that there was water leaking into #1 (away from the cam chain) from the head gasket? It could have been steam cleaned. #2 is the one that had poor compression, correct?

Thanks for your time and comments. I'll be investigating further, and I'm sure will have more questions.

Oddly this motor wont run if it doesn't have 125 psi or better. Both I and Racer x have experienced this.

Yeah, I'll believe that, the manual gives a lower service limit of 139 psi (engine hot at 470rpm WOT) Not sure how fast the starter turns the engine?

Do I need the special tool to take the pistons off the rods?

Oddly this motor wont run if it doesn't have 125 psi or better. Both I and Racer x have experienced this.
Me too on both cylinders.

Do I need the special tool to take the pistons off the rods?

I just used a small flat blade screwdriver to remove the pin clips and pushed out the pins by hand.

Definitely that one valve is running hotter. Pistons look good between the rings but that's just one perspective. I do agree with ninjinski's assumption.

This morning I did the leak test by pouring gas on top of the valves. It did leak, but it was very slow. The #2 seemed to leak a little faster.
Then I removed the valves.
One picture shows a valve sticking half-way out. I had difficulty removing that one. It seemed to slide fine in the guide, but the end didn't want to pass through for removal. Some twisting got it out. I haven't determined the cause, as the valve doesn't appear bent.

Here are the most recent pictures. Any more insight?

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11620
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11619
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11618
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11617

the valves should NOT leak at all. they need to be air tight. also, when the valve passes through the guide there should be some resistance as it needs to be a tight fit, but it should move freely and not get caught.

One thing you did not mention is what valve was leaking. If you poured gas on the valves the chamber would be wet near the offender. I'm interested to know what one leaked.

Ninjinsky good call on the valve being a different color. I see what you meant by this in reading through the posts and not focusing on the one issue I was debating.

headshrink take your head to a shop and have a valve job done. While there, have them check the guides. Also, you still need to fix that scratch as it is leaking combustion pressure in addition to your valve.

The valve you had trouble getting out is an inlet and is stuck way beyond its normal travel so I don't think you have a sticking valve problem there its the rocker end of it that might be a little swaged or burred. Slipping it back gently will show you what point it sticks at.
I would like to see the back (seat face) of the odd colored valve if you can get a shot of it
How did the middle ring gap look on the scratched cylinder ? I think mgentz and I have a mutual e-beer on it :D

the valves should NOT leak at all. they need to be air tight. also, when the valve passes through the guide there should be some resistance as it needs to be a tight fit, but it should move freely and not get caught.

One thing you did not mention is what valve was leaking. If you poured gas on the valves the chamber would be wet near the offender. I'm interested to know what one leaked.

Ninjinsky good call on the valve being a different color. I see what you meant by this in reading through the posts and not focusing on the one issue I was debating.

headshrink take your head to a shop and have a valve job done. While there, have them check the guides. Also, you still need to fix that scratch as it is leaking combustion pressure in addition to your valve.

The valve you had trouble getting out is an inlet and is stuck way beyond its normal travel so I don't think you have a sticking valve problem there its the rocker end of it that might be a little swaged or burred. Slipping it back gently will show you what point it sticks at.
I would like to see the back (seat face) of the odd colored valve if you can get a shot of it
How did the middle ring gap look on the scratched cylinder ? I think mgentz and I have a mutual e-beer on it :D

I realize by your comment that I did the leak test upside down. I suppose I'll need to reinstall the valves to retest. Should I go ahead and clean it all up first, or leave it dirty to get an initial result?

I agree that the stuck valve is likely not a problem. It feels like it only gets stuck at the very end, and has no problem moving before that point.

I haven't been able to inspect the rings yet.

I should mention that I do have a spare engine; or rather I'm using a spare engine. I'll inspect the original engine also to see if I can just throw the head on and be good without machining. I remember the compression being low before I swapped it out, but it was operating fine. The reason for the original switch was a bent input shaft due to a crappy clutch holder, overly tight nut, and breaker bar. Remember my goal is to fix it to sell, so it doesn't have to be at peak performance, and I don't want to spend money on it if I don't have to.


EDIT: What do we think of THIS (http://youtu.be/sUTFVyGFY_s)method of repairing the valves/seats

EDIT: What do we think of THIS (http://youtu.be/sUTFVyGFY_s)method of repairing the valves/seats
If the cup is small enough for ninja valves. I just use the stick rolled between the hands type.


Of course he just got grinding paste all over the stem, don't do that :rolleyes:

I'd just do the head swap Why drink flat beer when there's cans in the fridge :)
Indeed compare the other barrels and pistons too

If the cup is small enough for ninja valves. I just use the stick rolled between the hands type.
https://www.cromwell.co.uk/images/product/SYK/503/SYK5036904T_0.jpg
Of course he just got grinding paste all over the stem, don't do that :rolleyes:

I'd just do the head swap Why drink flat beer when there's cans in the fridge :)
Indeed compare the other barrels and pistons too

But beer is drunk from frosty mugs, never cans (poor college beer):smile-beerglass:

Sounds like a plan. If the other cylinders are acceptable I assume I should match them to the valves and cylinders that came with it...

But beer is drunk from frosty mugs, never cans (poor college beer):smile-beerglass:

Sounds like a plan. If the other cylinders are acceptable I assume I should match them to the valves and cylinders that came with it...

Keep the pistons and barrels in sets. The rings wear a slight step at the top of the cylinder in a high miler like this pic "credit "dans motorcycles")
http://www.dansmc.com/Hone_cyl_ridge.JPG
and the top ring can hit it if there is a slight mismatch
Though you are probably OK its best to keep the parts that have bedded in together as sets
You should be able to swap the head complete but be very careful with the valve timing, getting it wrong will do huge damage on the first rotation. I know that on mine the timing marks on the crank are really hard to see. So double check and when its together turn the engine gently by hand to make sure nothing hits anywhere.
Do you have the Kawasaki manual?
Here is a slow but thorough video on installing Ninja cams (you may like to check out parts 1 to 4 also)
7-noceisYm4
PS Important: This is a pregen, could someone confirm the later engine (which I have never stripped) is the same to time? ie using T2

One thing I disagree with so far is that no matter what at this point you need to at least put new rings into the motor. The valves can be blasted and hand lapped to get a good/decent seal. From there, assemble the motor break it in, then re-check compression. If you happen to have a brush hone, do a light hone on each of the cylinders before re-assembly.

The valve you had trouble getting out is an inlet and is stuck way beyond its normal travel so I don't think you have a sticking valve problem there its the rocker end of it that might be a little swaged or burred. Slipping it back gently will show you what point it sticks at.
I would like to see the back (seat face) of the odd colored valve if you can get a shot of it
How did the middle ring gap look on the scratched cylinder ? I think mgentz and I have a mutual e-beer on it :D

I don't think he has a sticky valve problem either based on the travel in the picture. However, it is still odd that it got stuck at all as there should be no sticking points. e-beer it is. :D

I kind of got into taking things apart, and am continuing to strip the spare (original) engine. I plan to split the case and swap internals so the VIN on the engine matches the frame. Things are moving, but I'm stuck at removing the alternator rotor. Apparently I need a puller. Do I need the Kawi one, or a certain type of generic puller?

I kind of got into taking things apart, and am continuing to strip the spare (original) engine. I plan to split the case and swap internals so the VIN on the engine matches the frame. Things are moving, but I'm stuck at removing the alternator rotor. Apparently I need a puller. Do I need the Kawi one, or a certain type of generic puller?
Now I am confused :confused: Why are you doing that and not just swapping the head barrels and pistons?
ps Then send the updated number to the registration authority so it is all legit.

It is common to have a raised ridge where the retainers grip the valve stem. This raised ridge is larger in diameter than the valve stem itself. I take an oil stone to the valve stem in that area before removing any valves to prevent damaging the valve guide by forcing the valve thru.

The pistons look good, at least in that there is no strong evidence of blow-by. The ring lands are clean, as well as the skirts. The rings are not discolored.

The exhaust valve seats on the other hand look very bad. I will view the pics on a different monitor with higher resolution when I get to work.

While not being a common garage tool, a leakdown gauge would have pinpointed the problem area immediately. My money is on the exhaust valves/seats. And if so, it is very doubtful that "cleaning" them will have any real benefit. If the valve face is worn "grooved, or curved" the valves require refacing or replacement. The seats, if pitted or too wide, will require refinishing.

Now I am confused :confused: Why are you doing that and not just swapping the head barrels and pistons?
ps Then send the updated number to the registration authority so it is all legit.

Well, it's been a while since I researched it, but it was pretty convoluted. I got the engine off ebay, am not sure I have the proper paperwork, and don't want a penalty for "unofficially" using the engine for two years. Since I'm having fun with all the learning, it seemed like the right time.

I got the flywheel off with a rented puller from autozone.

I'm ready to pry the case apart (have all the bolts out), but I haven't a clue how to go about it. The service manual wasn't very helpful here.

Well, it's been a while since I researched it, but it was pretty convoluted.etc'

I see, given the way google and the nsa are going you may wish to edit that your post into history then :D

I see, given the way google and the nsa are going you may wish to edit that your post into history then :D

LOL, I suppose so.

Any advise on getting the case to separate?

just pull. if everything is out it should slide apart relatively easy. there are case separation points (look like flat squares on opposing sides of the case offset from each other... pry points i think they are called) but you should be able to separate them with your hands only. the copper oil pipe gets tricky maneuvering it out. and the clutch has to come off to even get the bolt for it off. also theres bolts under the oil filter


don't force anything.

just pull. if everything is out it should slide apart relatively easy. there are case separation points (look like flat squares on opposing sides of the case offset from each other... pry points i think they are called) but you should be able to separate them with your hands only. the copper oil pipe gets tricky maneuvering it out. and the clutch has to come off to even get the bolt for it off. also theres bolts under the oil filter


don't force anything.

Working on it. I followed direction in the SM, but don't know if they missed something. In the past I've found occasional errors. I believe I have all the bolts out. I don't think the SM mentioned the copper pipe, but I took that bolt off to be sure. Clutch and flywheel are also off. I'll keep at it, but it wasn't budging before.

did you check under the starter motor

did you check under the starter motor

I did.

EDIT: GOT IT! There were two bolts inside the oil filter housing I had missed.

I think I'll be using the cylinders and head/valves from the original engine, not the one I took off the bike which was pictured above. It seems like it's in better condition, and although I don't recall what the compression was when I stopped using it, I do remember it was wnl (although not great).

How do these look?

Before valve removal
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11704

After several minutes it's still holding!
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11705

Cylinder 1 seats and valves
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11708

Cylinder 1 seats
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11709

Cylinder 2 seats and valves
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11707

Cylinder 2 seats
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11706

Cylinder 1
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11711

Cylinder 2
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11710

Pistons (with a little blow-by?)
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11714

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11713

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11712

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11715

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11716

You are doing a great job documenting this :clapping:
Looks good to me, just clean that carbon off the head and piston crowns, being careful not to slip with the tool and scratch the head face. It doesn't need to be spotless, just get those heavy flaky deposits off.
(optional) give the exhaust valves a quick dress with fine paste to get a gray line around but don't over do it (and obviously make sure you get all the paste cleaned off when you are done)
reassemble, new head gasket (and base gasket unless you were really lucky when it came off )

ps I am still curious about the cylinder scratch and middle rings on the faulty engine, It is irrelevant now but were the middle ring gaps the same on both sides?

Thanks.

The paste that you're referring to... are you talking about lapping the valves? Also, I'm not sure what you mean by a gray line.

Would you still recommend new rings and/or honing the cylinders (increasing compression would be awesome if this would help)? I did mix up the cylinders at some point, so I can't for sure match them. (Also not sure about the ring gap and scratch on the other engine... I'll see if I notice anything, but didn't before.)

When I remount the head to the case, do I just reuse the metal gasket with no sealants?

Will I be able to advertise this as a "rebuilt engine," or do I have to do something specific to claim that?

Thanks again for all the help. The aggravation is turning to fun now... just trying to go slow and keep cost down.

* One thing I learned last night: rather than injuring wrists by cranking the bold on the gear puller, banging with hammer, over and over again. An impact wrench on the puller is awesome! Now I can finally give Auto Zone their tool back.

Okay
1/ Valve grinding paste is abrasive powder in grease You are looking to get a clean ring of metal right round the valve by lapping. This guy shows how though actually his valves are already good!
/shkpkByfCE8

2/ If I remember one of the cylinders had a deepish vertical scratch, use the other ones.

3/ The metal head gaskets I used have a rubberised black coating which tends to peel in places when you take the head off so I used a new one. Other poster can advise on whether they have reused old ones successfully

4/ The bottom barrels to crankcase gasket you can probably reuse if it is not damaged as it is not subject to combustion pressure like the head gasket.
On modern aluminum threads Mr Torque wrench is your friend, go by the book and don't be tempted to "give it a little bit extra"

5/ Regarding the morality of descriptions (and life generally)
If you tell the truth you don't have to remember anything.
Mark Twain

6/ Yes learning is a pleasure, now you can look at a ninja engine and say to yourself "I know whats in there and how it works. It is very empowering. There are always mistakes to make though. I broke a ninja rocker a few months back, indeed that is what got me back on the site.
Have fun.:)

Thanks for the clarification. I just returned from Auto Zone with the lapper tool and paste.

I'm pretty sure my metal gasket didn't have any rubberized stuff on it, but there was a very small amount of goo that I wiped off. it was clear in color. Would copper gasket spray be appropriate, or just slap the metal in there and torque down?

Depending on the heat today, I may wait until tonight to do anything of significance.

EDIT: aaand.... the suction cups on the lapper tool are way too big :(

.

EDIT: aaand.... the suction cups on the lapper tool are way too big :(
yes, car ones are too big for our dinky valves, I will make you feel better by saying that you can get away without doing it as your valves are sealing pretty good anyway :)
My bike is a pregen so they have obviously changed the head gasket arrangement/ material. I don't know :o So we need advice from series two side of the house. Meanwhile you can decarbonize and reassemble the valves and springs.

Fortunately the other auto parts store in town sells the size small. Auto Zone only had the Large, and I didn't measure like I should have. I'm off to exchange it in a bit. But before I do, I've got some measuring to do.

UPDATE:

It's slow going, but I finally got the valves cleaned up, lapped, installed into head, and tested for liquid leakage.

Lapped, and ready to reinstall.
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11867

Although I suspect the slightest amount of leakage, this is after a few minutes holding kerosine.
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11868

You get an "A" for effort, but the seats are far too wide. The seats need to be cut to correct the issue, either by SERDI, or the traditional 3 angle grind method.

Same with the valve faces if they are cupped. I have no idea if they can be refaced due to construction materials. (some valves are face hardened, and refacing will remove the hardened surface, resulting in extremely rapid wear).

You did a great job of cleaning everything up without damaging any surfaces, and it all looks great, but sadly, needs more work to be durable and reliable long term.

Does it look like it will hold decent compression for a season or two? Remember my goal is to fix it up to sell. I eyeballed the other head, which has about the same mileage, and the seats looked very similar in wear.

All the exhaust valves do appear to be somewhat out of spec., although they were all very close to each other. The intake valves were in a little better condition.

I just took more detailed pics for reference.
Note: The (F) template is the proper seat thickness, according to the SM.

EXHAUST VALVES/SEATS
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11870

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11869

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11874

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11873

INTAKE VALVES/SEATS
https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11872

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11871

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11876

https://www.ninjette.org/forums/picture.php?albumid=1040&pictureid=11875

Wow. They look pretty warn as Harry said. I would imagine if you lapped the the valve face and seats smooth they would hold fine.

Wow. They look pretty warn as Harry said. I would imagine if you lapped the the valve face and seats smooth they would hold fine.

It's got about 20K on that head, which I imagine isn't a ton. Is there something I may have done to screw it up? I was always rejetting, in search of jettopia. If my valve lashes were done wrong maybe? I don't know, I'm grasping for answers. The original head has the same mileage, and the seats look pretty similar. I suppose I'll continue forging ahead. As a last resort I could always get a wrecked one off ebay, but I'd like to spend as little money as I reasonably can.

2L and 2R valves have some good erosion. I'm still new to engine-valve dynamics. maybe excessive carbon build up on the seats/valves to cause the valve to not seat fully. I'm just taking a stab.

The problem with worn seats is that carbon particles get trapped and stick to the valve or seat leaving the small circular pits visible in the pictures. This upsets the seal and leads to erosion ("burned valves").

Also, the wide seats seal poorly to begin with. (witness the fluid leaking past).

To repair it, the seat needs to be "brought up" by cutting a steeper angle on the bottom of the seat, and a shallower angle on the top, leaving a narrow seat for the valve to seal against.

Reasons for valve and seat wear are continuous high rpm, excessively loose valve clearance, and poor air filtration. Worn valve guides accelerate the process.

The problem with worn seats is that carbon particles get trapped and stick to the valve or seat leaving the small circular pits visible in the pictures. This upsets the seal and leads to erosion ("burned valves").

Also, the wide seats seal poorly to begin with. (witness the fluid leaking past).

To repair it, the seat needs to be "brought up" by cutting a steeper angle on the bottom of the seat, and a shallower angle on the top, leaving a narrow seat for the valve to seal against.

Reasons for valve and seat wear are continuous high rpm, excessively loose valve clearance, and poor air filtration. Worn valve guides accelerate the process.

Thanks for the explanation.

I may continue to build with what I have, but swap it out for an ebay head if the compression tests too low.

EDIT: Scratch that. My gut is telling me I should probably just replace the head NOW with a low-milage ebay head/valve combo. There is just too much compromise trying to reuse existing parts. I'm also afraid the cost of all the little valve parts I may need to replace would make it way more expensive than just going with ebay now. Paychecks have been abysmal, so I'll still be crawling for awhile.

Dont worry with few black spots on the seat. As long as the valves seal fine and the seats are within tolerances as stated by the manual, it's still okay. The exhaust valves of 1L 2L, 2R, and intake valves of 1R and 1L looks worn. If you get valve that has sharp edges like below it cant be used anymore:

http://gambar.otomotifnet.com/Kanal%20MOTOR/Tips/2011/01-Januari/20110105KlepNinja_Lead.jpg

They may be last forever, or just few months if the new rider abuse it daily. What I mean of abusing is he/she redline the bike without shifting up, running 60 mph on second gear for an hour daily. Any engine can be destroyed if ridden like that, even supersport engines. If you are cheap, only replace the intakes, the exhaust valves can withstand more abuse than the intakes. Did you use aftermarket CDI that remove limiter?

May be you need new sims as well.

Yes to the CDI, but I didn't abuse it.

Does this (http://www.ebay.com/itm/K84-Kawasaki-EX-250-Ninja-250-2010-Engine-Cylinder-Head-w-Valves-/380981259347?pt=Motorcycles_Parts_Accessories&fits=Model%3ANinja+250R&hash=item58b440ac53&vxp=mtr)look like a good Ebay replacement?

Does this (http://www.ebay.com/itm/K84-Kawasaki-EX-250-Ninja-250-2010-Engine-Cylinder-Head-w-Valves-/380981259347?pt=Motorcycles_Parts_Accessories&fits=Model%3ANinja+250R&hash=item58b440ac53&vxp=mtr)look like a good Ebay replacement?

Sure does. I haven't look around so I'm just going off the info provided.

I'm getting ready to order it.

Do the pics of the valves look like they are running at proper temp?
Also, they are clean around part of the valve circumference, and some blackened parts. Might this indicate any blow-by, or is it meaningless?


EDIT: Cylinder head is on its way!

Now perhaps this is an overly-cautious question, but should I remove and clean the valves/seats on the new head when it arrives, or might this run the risk of disturbing it's current bedded-in seal?
Might I then need to lap the valves after removal?
I'm not sure if this is just an OCD detail, or actually good practice. It's all new to me.

Received the new cylinder head and valves. The oil left over in it is red...... is this a thing? Please tell me someone didn't put trans fluid in it.

Possibly this?
http://www.raceshopper.com/images/eng5w30.jpg

Yes... it's actually red.

*big sigh of relief* I'm sure that's it. Thanks.