Did my 250 become a 125 (dead cylinder)?

[headshrink]

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/showt...615#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?

[Racer x]

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

[headshrink]

Originally Posted by Racer x

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.

[Racer x]

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.

[silentIm]

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.

[headshrink]

Originally Posted by silentIm

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.

[silentIm]

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.

[headshrink]

Originally Posted by silentIm

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?

[silentIm]

Originally Posted by headshrink

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.

[dcj13]

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.

[alex.s]

check spark on the new coil

[headshrink]

Originally Posted by dcj13

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.

[headshrink]

Originally Posted by alex.s

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.

[jkv45]

Originally Posted by headshrink

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.

[alex.s]

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

[dcj13]

Originally Posted by alex.s

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.

[alex.s]

Originally Posted by dcj13

I'm a lazy guy

i hear ya

[Motofool]

Originally Posted by dcj13

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.

[dcj13]

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.

[headshrink]

Originally Posted by jkv45

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.

[headshrink]

Originally Posted by Motofool

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.

[headshrink]

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?

[Motofool]

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.

[headshrink]

Originally Posted by Motofool

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.

[headshrink]

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?

[headshrink]

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?

[cuong-nutz]

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.

[Runeknight95]

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

[headshrink]

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.

[cuong-nutz]

Which wire are you referring to?

[silentIm]

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.

[headshrink]

Originally Posted by cuong-nutz

Which wire are you referring to?

The spark-plug wire.

[headshrink]

Originally Posted by silentIm

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.

[Ninjinsky]

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.

[silentIm]

Originally Posted by headshrink

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

[headshrink]

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

[silentIm]

Originally Posted by headshrink

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.

[headshrink]

Originally Posted by silentIm

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.

[mgentz]

How did this end up?

[headshrink]

Originally Posted by mgentz

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.