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Discussion Starter · #1 ·
Recently bought 2006 TRX250ex, cleaned the carb, changed the oil, new plug and air filter. Son's bike, has been running great until the other day. He was running in 3rd gear when he heard what he described as a small bang or crack, bike died and won't restart. The starter is new and spins fine, bike does not turn over at all, it almost sounds like the starter gear is spinning but nothing else. Could this be a timing chain or tensioner?
 

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Welcome to the forums! will it push start? if it won't push start then i would say its locked up.
 

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The easiest thing to do is remove the spark plug then remove the rear cover the thin metal plate on the back of the engine close to the shock grab a 17mm socket and try to turn the engine over manually. if it won't the I agree with 69 your seized-up
 

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Welcome to the forums. If it sounds like just the starter motor is turning, it might be the one-way bearing in the starter gear on the back of the flywheel. When they go bad, the starter will just spin and the engine won't turn over, but I've never heard one make a bang or cracking sound. You'll have to pull the flywheel cover off and see.
 

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Oh yeah Welcom to the forums..... I have to say the 250EX is practically an indestructable bike like it's twin the Recon they are one of the best bikes out there. just my two lincolns..
 

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Discussion Starter · #6 ·
thanks guys, it will not push start either. I will pull the cover and check the flywheel, hopefully the motor didn't break.
 

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I think Helmut forgot to tell you to put it in like 3rd or 4th but try turning at the flywheel. How does the oil level look now? and what kind of oil did you put in it?
 

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Discussion Starter · #8 ·
I used the Honda specific oil, I was able to turn the flywheel but I don't believe the piston is going up and down, possibly a timing chain or chain cam? The flywheel rotates like it should as though it's turning the crank.
 

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Ok then all isn't lost so far... remove the plug and take a new pencil. I say pencil because if you bind up a screwdriver you run a risk of damaging the threads. stick it in the plug hole and rotate the flywheel again you should feel the piston come up and touch the pencil. you can also use a pen light and look in the hole too.
 

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Discussion Starter · #10 ·
I did try that, I used a long tie wrap, it didn't move nor do I feel any compression when I rotate the motor. So either something in the rotating mass let go or the timing chain....I think, I don't know squat about these motors unfortunately.
 

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The timing chain isn't going to prevent the piston from moving. you need to try something heavier than a zip tie remember to rotate the engine counterclockwise. if at all possible shine a light down into the plug hole and look and see if you can see anything going on.
 

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If the flywheel is turning and the piston isn't moving, then either it sheared the flywheel key or your crankshaft is broken.
 

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If the flywheel is turning and the piston isn't moving, then either it sheared the flywheel key or your crankshaft is broken.
Agree ^^^^ I think I would lean toward the Key.
 

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Discussion Starter · #14 ·
well neither, the connecting rod broke. Took out the cam, piston, sleeve, possibly the crank....basically the whole block. Couple of questions, I just rebuilt the carb and had backed off the fuel mixture screw because previous owner had it all the way in. When I rebuilt the carb the slow jet was just sitting in the bowl, no wonder the thing was sucking fuel and running rough. Anyways I don't believe I leaned it out that much it showed no other signs of running that lean, plug was slightly tan but otherwise normal. Previous owner is a quasi-friend, he says I leaned the motor out too much (we only ran it for an hour or so after carb rebuild), I believe his teenage kid over-revved the motor and stretched the connecting rod, it breaking was bad timing.....what do you guys think?
 

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These engine cannot be over rev'ed they do have a rev limiter on them, unless an aftermarket CDI was installed then it will raise the rev limit by a grand. lack of oil would be the probable cause. ie. the oil pump quit.
 

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Discussion Starter · #16 ·
thought about that, or possibly water in the cylinder at some point maybe bent or weaken the rod. Not sure what we're doing yet, prolly cheaper to replace the motor than try and replace all the parts. Any leads on a used 06 250ex motor? btw, could I use a 300ex motor for this bike, I think those are driveshaft bikes also, right?
 

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btw, could I use a 300ex motor for this bike, I think those are driveshaft bikes also, right?
No, the 300EX is chain drive.
 

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thanks guys, very informative site you guys have here.
You can rebuild this engine for far less than buying one that you know nothing about. Give me a little bit I will try to find you what you need.
 

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Ok the complete gasket set for the whole engine is 75.00 at KB Motorsports one of our vendors. At Dennis Kirk you will find the following......
Vesrah Connecting Rod Kit
Dennis Kirk Part #: 148278
Manufacturer Part #: VA1015
Vesrah Connecting Rod Kit
Your Price: $103.99
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This is stock bore...
Wiseco Piston Assembly
Dennis Kirk Part #: 4935M06850
Manufacturer Part #: 4935M06850
Wiseco Piston Assembly
Your Price: $138.99
You should be able to rebuild this engine for about 550.00 if you do it yourself. that's all new insides piston, connecting rod, gaskets, and wrist pin, clips and rings. hope this helps

Oh yeah another sleeve if you need it.
L.A. Sleeve Cylinder Sleeve
Dennis Kirk Part #: H5366
Manufacturer Part #: H5366
L.A. Sleeve Cylinder Sleeve
Your Price: $83.99
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Moose Crank Bearing/Seal Kit
Dennis Kirk Part #: 149657
Manufacturer Part #: 09240050
Moose Crank Bearing/Seal Kit
Your Price: $36.95
 
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