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Posted by: madmike90---------------------

so today i was riding my '96 cr125 on a real long straightaway (few miles)

i was in the top gear and was varying the revs around and in and out of the sweet spot of the powerband but staying in that gear for about a 1/4 mile.

as i slowed down to stop and shifted as normal down through the gears when i got to 1st gear and almost stopped i heard a lot of clanking and it seemed to be slipping in and out of gear.

i thought i had done damage from the motor from keeping it on a sustained 5th gear run but now that i think of it, i think it might be the transmission, because when i start the bike up the revs build up and go through the roof without noise, leading me to believe the jug and piston are as normal.

what could the problem possibly be?
broken basket, plates?


Posted by: whenfoxforks-ruled---------------------

Drain the oil, you killed it. Vintage Bob


Posted by: madmike90---------------------

Quote:
Originally Posted by whenfoxforks-ruled
Drain the oil, you killed it. Vintage Bob



killed the oil or killed the basket/gearbox?


Posted by: SS109---------------------

From all I have read, you shouldn't downshift through the gears when slowing from sustained high speed runs as it supposedly kills 2t's. I don't know why but I have followed that advice and my KDX200 has survived many sustained miles of 45, 50, and 55mph runs.

I wish I could help but that's all I got. Good luck and please update us when you find the problem.


Posted by: madmike90---------------------

Quote:
Originally Posted by SS109
From all I have read, you shouldn't downshift through the gears when slowing from sustained high speed runs as it supposedly kills 2t's. I don't know why but I have followed that advice and my KDX200 has survived many sustained miles of 45, 50, and 55mph runs.

I wish I could help but that's all I got. Good luck and please update us when you find the problem.


i dont downshift enough the make the revs scream up, i start downshifting basically when i'm almost at a stop. i'm not sure what the problem is here


Posted by: smahala1286---------------------

Quote:
Originally Posted by SS109
From all I have read, you shouldn't downshift through the gears when slowing from sustained high speed runs as it supposedly kills 2t's. I don't know why but I have followed that advice and my KDX200 has survived many sustained miles of 45, 50, and 55mph runs.

I wish I could help but that's all I got. Good luck and please update us when you find the problem.


it kills 2t's because with the throttle closed there isn't much lubrication being introduced into the crankcase. That combined with the crank spinning high rpm will cause a lot of friction and heat usually resulting in seizure.


Posted by: madmike90---------------------

Quote:
Originally Posted by smahala1286
it kills 2t's because with the throttle closed there isn't much lubrication being introduced into the crankcase. That combined with the crank spinning high rpm will cause a lot of friction and heat usually resulting in seizure.


ah i see.

well thankfully, the engine turns over and is not seized as well as runs and sounds smooth, but the revs immediately skyrocket when the bike starts up which is what im trying to figure out.


Posted by: SS109---------------------

Quote:
Originally Posted by smahala1286
it kills 2t's because with the throttle closed there isn't much lubrication being introduced into the crankcase. That combined with the crank spinning high rpm will cause a lot of friction and heat usually resulting in seizure.

Makes sense!


Posted by: IndyMX---------------------

You can get a million people on here tell you a million and one things, however, you still have to take the engine apart to inspect the damage.

The bike will not fix itself, get the wrenches out and get turnin.


Posted by: RM_guy---------------------

Quote:
Originally Posted by whenfoxforks-ruled
Drain the oil, you killed it. Vintage Bob
At a loss for words??

Drain the oil and see what comes out. It's hard to say what happened but I'd start with that. If no chunks of metal come out then it may not be the tranny but I'd still pull the clutch side cover off anyway and just take a look...exploratory surgery.


Posted by: whenfoxforks-ruled---------------------

Quote:
Originally Posted by RM_guy
At a loss for words??

Drain the oil and see what comes out. It's hard to say what happened but I'd start with that. If no chunks of metal come out then it may not be the tranny but I'd still pull the clutch side cover off anyway and just take a look...exploratory surgery.
Yes, what he said! You have to start somewhere, besides here? You are going to tell us what happened, its in your garage. Vintage Bob


Posted by: madmike90---------------------

i just took out the clutch plates and baskets (inner/outer) and there are no broken plates but the plates have basically no friction material on them, the outer basket teeth have severe ridges, it almost looks like the ridges could be used as a sprocket in a pinch lol, they're that bad.
http://img11.imageshack.us/img11/811/pic0195v.th.jpg


Posted by: whenfoxforks-ruled---------------------

You would mike the plates to see where they are at. Nice drive side basket notches. Vintage Bob


Posted by: _JOE_---------------------

How's the inner hub look? That basket is impressive.


Posted by: RM_guy---------------------

Damn, you could use that basket to cut a tough steak with!


Posted by: madmike90---------------------

Quote:
Originally Posted by whenfoxforks-ruled
You would mike the plates to see where they are at. Nice drive side basket notches. Vintage Bob


the plates are definitely shot, the friction material can barely be felt when you run your finger over the bumps. as far as the metal plates i'm not sure where they're at but they come with a clutch plate kit correct?

when i opened up everything up, everything else looked perfect, i took the head off and worked the piston up and down and it the piston and cylinder are perfect.

so, what i dont understand is why when i started the bike with the basket and plates in, why did the revs want to climb and go through the roof?

is the motor under a constant small load even in neutral or something?


Posted by: whenfoxforks-ruled---------------------

Your engine displayed a lean condition. Either running out of fuel, or lean? Vintage Bob


Posted by: madmike90---------------------

Quote:
Originally Posted by whenfoxforks-ruled
Your engine displayed a lean condition. Either running out of fuel, or lean? Vintage Bob


thats a possibility, i had half a tank of gas so no problem there, the fuel mix is the same as always and i didnt do any jetting and it hasn't been running lean since i've had it.

the single only problem i could find on the bike was the condition of the plates and basket, but i don't understand how that could make the revs want to skyrocket.

i checked the carb boot for vacuum leaks and everything is sealed up nice and tight.


Posted by: Bodge---------------------

Left side crank seal?


Posted by: _JOE_---------------------

I second the crank seal, pull the ignition cover and see if it's at all oily behind the flywheel.


Posted by: madmike90---------------------

hmmm no oil behind the cover, still stumped.

i thought that the only reasons why a motor will increase in revs is more air or more fuel or possibly less load?
theres no air leaks i can find.


Posted by: whenfoxforks-ruled---------------------

The tranny is not blown, the clutch is blown, and no residue behind the stator plate. You said it was slipping in and out of gear, that was probably the clutch. The increase in revs, theorized to be from less load? While you was riding it, thats the clutch slipping, no load. On the stand, no, probably not enough fuel getting into the engine. From the gas cap venting to dis-assembling/cleaning/inspection of the carb. Do not forget the screen on the petcock inside the tank. When was the last time you changed the plug? If your increase in rpm was due to loading up, do you give more throttle till it clears out? The plug could tell if the revs are from a lean condition. Pulling the head off, why not the top end? How long since the last top end? It would only cost you a base gasket and set of rings, if its still with in spec. Moving the piston up and down really misses the important part, measuring the ring end gap, and skirt clearance. Looking good always counts, but, a feeler gauge is cheap insurance. If it is a lean surge, next time throw the choke on and see if it runs better? Vintage Bob


Posted by: madmike90---------------------

Quote:
Originally Posted by whenfoxforks-ruled
The tranny is not blown, the clutch is blown, and no residue behind the stator plate. You said it was slipping in and out of gear, that was probably the clutch. The increase in revs, theorized to be from less load? While you was riding it, thats the clutch slipping, no load. On the stand, no, probably not enough fuel getting into the engine. From the gas cap venting to dis-assembling/cleaning/inspection of the carb. Do not forget the screen on the petcock inside the tank. When was the last time you changed the plug? If your increase in rpm was due to loading up, do you give more throttle till it clears out? The plug could tell if the revs are from a lean condition. Pulling the head off, why not the top end? How long since the last top end? It would only cost you a base gasket and set of rings, if its still with in spec. Moving the piston up and down really misses the important part, measuring the ring end gap, and skirt clearance. Looking good always counts, but, a feeler gauge is cheap insurance. If it is a lean surge, next time throw the choke on and see if it runs better? Vintage Bob


hey man there was a lot of info there i got kind of lost. I'll answer what i could pick out.
The plug was just changed about 3 hours ago and when i took the head off, it looked normal.

The carb was just gone over and cleaned thoroughly and the bike ran great as it was.

The top end was done 5 hours ago and was broken in correctly with no issues.

when i get the new plates and basket, ill try to start it up again and see if everything's good, because i know at very least, that is what i need.


Posted by: RM_guy---------------------

Quote:
Originally Posted by madmike90
hey man there was a lot of info there i got kind of lost. ...
Welcome to Vintage Bob land LOL

You said there were no air leaks but did you do a leak down test? Not seeing oil behind the stator is not very conclusive.

Also check to make sure the throttle cable isn't snagged on something. twist the throttle, let go and listen to hear if the slide is bottoming out on the idle screw in the carb. It will make a solid clunk.



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