Bike not wanting to rev past ~5k while driving

[FvnnyL3tt3r1ng]

I normally do keep the petcock closed.

I have not tested for spark, I am about to do this. You just crank the engine while looking at the spark gap correct?

I went WOT during cranking and the engine sound doesn't deviate any.

I backed out the idle mixture screws 2.5x

I just got some fresh 93 oct gas so I can eliminate water in the tank. I saw that water was heavier than fuel so I'm guessing it would enter the engine first, however it wasn't raining in between the time I had the bike running and the time it refused to start....

[alex.s]

Originally Posted by FvnnyL3tt3r1ng

I have not tested for spark, I am about to do this. You just crank the engine while looking at the spark gap correct?

the spark plug body needs to be in contact with the bikes ground (unpainted engine side cover (not the valve cover), battery negative etc)

[FvnnyL3tt3r1ng]

Spark plugs both work (I felt how well too). I'm starting to think I have damaged something in the engine to cause the compression to drop. I've eliminated everything it seems. What makes the engines compression drop??

The bike ran fine after I adjusted the valves could they have messed up somehow afterwards???

I do have an excuse to buy an air compressor + leak tester now....

Bad engine timing? I'm not too familiar with this department...

Guess I'll be re-doing the valves...Was hoping to have the kawi tool by the next valve clearance.

[choneofakind]

The whole frame is grounded as well. Just touch the spark plug to the frame or engine while the back it connected to the boot like normal, and watch it spark.

[Rollingmenace]

Originally Posted by FvnnyL3tt3r1ng

Spark plugs both work (I felt how well too). I'm starting to think I have damaged something in the engine to cause the compression to drop. I've eliminated everything it seems. What makes the engines compression drop??

The bike ran fine after I adjusted the valves could they have messed up somehow afterwards???

I do have an excuse to buy an air compressor + leak tester now....

Bad engine timing? I'm not too familiar with this department...

Guess I'll be re-doing the valves...Was hoping to have the kawi tool by the next valve clearance.

just something to keep in mind here is when running your leak down test it is best to use a bicycle pump a compressor may give you too much air pressure

[FvnnyL3tt3r1ng]

Originally Posted by Rollingmenace

just something to keep in mind here is when running your leak down test it is best to use a bicycle pump a compressor may give you too much air pressure

That saves me loads. I'm thinking a nut came loose in the rockers though. Don't air compressors have a cut off setting? I'd still like to do it for xperience/fun/nerd in me.

[FvnnyL3tt3r1ng]

Originally Posted by choneofakind

The whole frame is grounded as well. Just touch the spark plug to the frame or engine while the back it connected to the boot like normal, and watch it spark.

Yeah I did it arced a la Ghostbusters and the right one "bit" me so I felt the POWER!

[Rollingmenace]

Originally Posted by FvnnyL3tt3r1ng

That saves me loads. I'm thinking a nut came loose in the rockers though. Don't air compressors have a cut off setting? I'd still like to do it for xperience/fun/nerd in me.

Nothing wrong with having toys for the garage .. I'm actually working on my own powder coating setup in mine I'm building oven myself.. As far as leakdown testing these ninjette motors I haven't read up on it yet but on the single cylinder 2 stroke motors I build we only use about 10psi and there would be no way to do that with my compressor hence using the bicycle pump.... If you really want to geek it up google leak down tester and you can build your own from stuff u can pick up at local hardware store for a fraction of the cost. Last one I put together for around 13 dollars

[Motofool]

Yes, 10 psi will force each piston down with a force of around 46 pounds, if big leaks wouldn't be present.

"Well, I think this is an interesting test that .......tells you where the leaks are and you don't even have to have the gauge to do it.

The test is simple. Apply air pressure to the spark plug hole and listen. You will probably have to take the exhaust pipe and carburetor off plus remove the oil fill cap. Other then that, just listen. You will need at least fifteen or twenty pounds of air pressure. Higher pressure will make the sound louder but too much and you will need to lock the crankshaft to keep the engine from turning. A hissing noise at the carburetor manifold indicated a leak at the intake valve(s). Hissing at the exhaust, leaking exhaust valve(s). Hissing at the oil fill or at the engine breather tube, leaking past the rings.

For air pressure you can use a fancy spark plug hole attachment or just a rubber tip on a blow gun. You might need an extension for these hard to reach plugs too."

[FvnnyL3tt3r1ng]

How would the valves affect compression? Would it leave a portion of the valve open in the cylinder making the leak? I was pretty sure all was well after I did the valve adjustment and ran the bike for a few min. afterwards....Hopefully nothing is broken

[Motofool]

Yes, if valves don't close perfectly or if their guides are worn out, compression will leak out and raw air will leak in (sucking less from the carbs).

Intake valves are typically larger than exhaust valves because the piston is moving away from it, creating a vacuum to pull a mix of air and fuel into the cylinder, which is not as efficient as pushing combustion gases out of the cylinder through the exhaust valves.

When new, valves close perfectly, since the angles of the cones are matching and the surface is perfect.

With time, and especially when working long time and hard out of specs (too little clearance), the surfaces may get damaged from not enough cooling (valve and head not together enough time) and hot exhaust gases leaking out.

Did you use a torque wrench and the recommended torque during your valve service?
Too little may let the nuts get loose and too much may break the rocker arms.

[FvnnyL3tt3r1ng]

Originally Posted by Motofool

Yes, if valves don't close perfectly or if their guides are worn out, compression will leak out and raw air will leak in (sucking less from the carbs).

Intake valves are typically larger than exhaust valves because the piston is moving away from it, creating a vacuum to pull a mix of air and fuel into the cylinder, which is not as efficient as pushing combustion gases out of the cylinder through the exhaust valves.

When new, valves close perfectly, since the angles of the cones are matching and the surface is perfect.

With time, and especially when working long time and hard out of specs (too little clearance), the surfaces may get damaged from not enough cooling (valve and head not together enough time) and hot exhaust gases leaking out.

Did you use a torque wrench and the recommended torque during your valve service?
Too little may let the nuts get loose and too much may break the rocker arms.

I did not use my torque wrench because I believe the reading was in newton-meters and I didn't know the conversion rate so I tightened sort of like the spark plugs, tight plus 1/8 turn or so

[Motofool]

I see.

That may be the source of the problems; so, it is worth removing the tank and valve cover for an inspection.

Check the proper torque here:

http://www.ninjette.org/wiki/Fastene...Specifications

[FvnnyL3tt3r1ng]

Took valve cover off, checked clearances, all was well.

Torqued to spec.

Bike won't start.

How would I go about putting fresh gas in? I have some in a container but doesn't the petcock of the tank have to be hooked up?

[FvnnyL3tt3r1ng]

How hard will it be to replace the piston ring(s) if I have to?

[FvnnyL3tt3r1ng]

I mean do you simply swap them on the piston? No special tools or procedure? Can I get to them by pulling off the "cylinder head"
http://www.kneedraggers.com/oem-part...mmy_source=oem

[Lychee]

After reading this thread, it is very clear that you are introducing problems while trying to fix others. You need to apply fixes for the problem at hand without doing other work that muddles the situation. While you are clearly capable of wrenching, it does not appear that you have the knowledge necessary to repair the current set of problems on the bike. I highly recommend you take the bike to a qualified mechanic. If you cannot afford the mechanic, you should junk/sell this bike now and buy another.

Take a step back and ask yourself if you should really risk your life riding this bike.

[FvnnyL3tt3r1ng]

Originally Posted by Lychee

After reading this thread, it is very clear that you are introducing problems while trying to fix others. You need to apply fixes for the problem at hand without doing other work that muddles the situation. While you are clearly capable of wrenching, it does not appear that you have the knowledge necessary to repair the current set of problems on the bike. I highly recommend you take the bike to a qualified mechanic. If you cannot afford the mechanic, you should junk/sell this bike now and buy another.

Take a step back and ask yourself if you should really risk your life riding this bike.

The thing is, I don't know WHAT the problem is.... If it's something as simple as a torn vacuum line in the carbs, I would feel extremely stupid having ditched this bike that I put so much time/money/effort into. Once I know what the problem is I can make a more informed decision. If I did in fact damage something in the engine I will def. consider ditching it but until I find out I have to keep trying.

[Motofool]

Originally Posted by FvnnyL3tt3r1ng

Took valve cover off, checked clearances, all was well.

Torqued to spec.

Bike won't start.

How would I go about putting fresh gas in? I have some in a container but doesn't the petcock of the tank have to be hooked up?

Great! Those are good news.

I couldn't understand your last question.

[FvnnyL3tt3r1ng]

Originally Posted by Motofool

Great! Those are good news.

I couldn't understand your last question.

Well I was asking how to put fresh gas in from an auxillary tank but I think i'll just drain the existing gas into a bucket.

[Motofool]

A full hose with the end up to the height of the tank would be sufficient.

If we cannot even start yet, you don't really need a tank.

The fuel inside the hose will give you several minutes of idle.

Storing gas in an open container is potentially dangerous.

[FvnnyL3tt3r1ng]

Originally Posted by Motofool

A full hose with the end up to the height of the tank would be sufficient.

If we cannot even start yet, you don't really need a tank.

The fuel inside the hose will give you several minutes of idle.

Storing gas in an open container is potentially dangerous.

I'm trying to rule out bad gas even though I doubt it's the issue.....

[Motofool]

Yes, that is a good idea.

The low compression is a fact.

We know now that all the valves are closing all the way; however, you still need to determine if surgery will be necessary due to leaky valves, leaky head gasket or leaky rings.

[coughing skunk]

Leak down test is certainly in order next to find out where you are losing compression.

I may have missed something in these four pages, but has the timing been addressed?

[FvnnyL3tt3r1ng]

Originally Posted by coughing skunk

Leak down test is certainly in order next to find out where you are losing compression.

I may have missed something in these four pages, but has the timing been addressed?

No it hasn't do you know how to check that?

[choneofakind]

Turn the engine to the 2T mark. There are white paint marks on the back of your cam gears. On one cam, this mark with be next to writing that says, "EX". On the other cam, this mark will be next to writing that says, "IN". The marks should be facing opposite ends of the bike, parallel to the cam cover.

If they're lined up right when the engine is at the 2T position, your cams are timed right.

[FvnnyL3tt3r1ng]

Before I start how did you guys manage to use a bike pump w/ the leak down gauge? Was it compatible with the gauge you were using or did you have to rig something up?

[FvnnyL3tt3r1ng]

Tried to do the air pump+leak gauges but I need my hands free to work plus the gauges don't seem too respond to the bike pump so I'm going to buy an air compressor (and run it at low psi).

When I blew air directly into the left cylinder the air came out of the vacuum line that goes to the petcock. I set the engine at TDC based on the readings ontop of the alternator.

I checked the timing by setting the alternator reading to the white line (2t?) and opened the valve cover. From the right of the bike the exhaust side points at 2 oclock and the left side points at 9 oclock...Not perfectly parallel.....

[choneofakind]

Originally Posted by FvnnyL3tt3r1ng

I checked the timing by setting the alternator reading to the white line (2t?) and opened the valve cover. From the right of the bike the exhaust side points at 2 oclock and the left side points at 9 oclock...Not perfectly parallel.....

Triple check that!!!!

There should be a 1T marking and 2T marking in there. Make sure you're at the 2T marking.

I've got pictures of how the cams should look from the 1T marking from when I had my engine apart, but they're easier to time from the 2T marking.

[FvnnyL3tt3r1ng]

Timing cover on alternator:



Left side of bike:




Right Side of bike:
(If you can't see the left mark is facing left and cut in half by the valve cover gasket and the right side is pointing up and to the right.

[FvnnyL3tt3r1ng]

Originally Posted by choneofakind

Triple check that!!!!

There should be a 1T marking and 2T marking in there. Make sure you're at the 2T marking.

I've got pictures of how the cams should look from the 1T marking from when I had my engine apart, but they're easier to time from the 2T marking.

Could you post the pic(s) please? I'd really like to check mine against yours.

[choneofakind]

When I did mine, the "EX" and "IN" markings were on the inboard side of the cam gears IIRC.

Look across the engine from the left side of the bike, like this:


There should be white markings that will face opposite ends of the bike, parallel to the cam cover. This picture is at the 1T mark. Notice on the intake cam gear, there's a little white mark facing up? At 2T that should be facing the back of the bike. There's a matching one on the exhaust cam that faces the front at 2T.

I can't see any markings on your flywheel in the picture... Maybe it's just because it's a camera

[Motofool]

The 2T mark means that the piston #2 is at the top dead position, position at which the four valves of that piston should be perfectly closed.

[choneofakind]

^^ Thanks Hernan!

That shows the "IN" and "EX" better than my picture, which only kinda shows the "IN" if you look at it. Not to mention, mine's at the wrong place in the cycle. Yours is better.

[Motofool]

You are the one helping, Chris; I am just supporting.

Note that both gears have the IN and EX stamped on, since they are both the same part.

The marks should align with the flat metal surface, not with the gasket.

Of course, the EX only applies to the camshaft closer to the exhaust and the IN only applies to the camshaft closer to the carbs.

To be more precise, count the number of links between marks, as the schematic shows.

[FvnnyL3tt3r1ng]

Originally Posted by Motofool

To be more precise, count the number of links between marks, as the schematic shows.

Are those the chain pins?

[FvnnyL3tt3r1ng]

The intake side is pointing 12 oclock and the exhaust is level with the metal piece pointing inwards...



exhaust side at TDC:


Intake side at TDC:


I'm not sure if the sprockets were just installed weird or the timing is actually off? Lemme check chone's picture against it first.....

If they are off what causes them to do this??

[FvnnyL3tt3r1ng]

Ok the rockers are facing the same direction as choneofakind's picture( and on both cylinders)....

Edit: Ok I realize now the position of the markings on the sprockets don't matter at TDC. I counted 33 links as the diagram showed....I guess the next step is the air compressor/stethoscope to find out where the leak is!!!

[FvnnyL3tt3r1ng]

Results of leakdown test are as follows:

Cylinder 1 (left):
>80%+ @ 10 psi (compressor could hardly even get to 10psi)

Cylinder 2:
~37% @ 10 psi (gauge said this was ok but I'm not sure if I should believe it)

Is it safe to assume cylinder 1 may be jacked up while cylinder 2 is fine?

I couldn't hear where the air was coming from btw, I did hear it hissing from the spark plug hole obviously but I couldn't locate it exactly, even with a stethoscope.

I remember one of the first replies was "Happened to me when I blew a ring on my cbr"

Looks like I will be doing surgery. I really wish this could have happened at another time.

[coughing skunk]

Yup, its most likely bad rings or bent valves.

I was asking about the timing because I thought it could be bent valves, esp since I *think* you said you had it running momentarily. If the timing was off you could've smashed your piston into a valve, bending it.