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1991 RM 250 runs for about an hour and cuts out! ???

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I've got a 91 rm 250 and it ran fine until this weekend. About an hour in to the ride it started sputtering and quit. Waited, got it started and back to the trailer. Checked plug,good, changed it out anyway, bike started right up and ran great for about another hour and did same thing but did have to catch it in gear to get restarted! Any clue? Thanks for your help!!!

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I had a stator fail on my 1978 RM-125.  Was out riding it one day and all of a sudden it died.  I must have kicked it a thousand times and nothing.  I pushed it all the way back to the truck, about two miles and fairly level so not too bad.  Sat around pondering what could be wrong for another hour or so and on a whim tried to start it again. If fired right up so back to riding I went.  It only lasted about 15 minutes and then it died again.  Pushed it back to the truck again, loaded up and headed for home.  Stopped by the Suzuki shop the next week and described what had happened.  They recommended that I check the resistance (continuity)  of the stator coils and told me how to do it.  So I went home, got the ohm meter out and started measuring.  Sure enough I had an open circuit.  I went back to the Suzuki shop and ordered a new stator assembly, not even considering what might have caused the original to open circuit.  I got the new part a couple of weeks later and installed it on the bike.  I kicked it over and it fired right up so I loaded it up in the truck and went out to ride.  After about an hour or so of riding the darn thing quit again.  I packed it up and went home.  This time I knew how to check the stator resistance and I did.  Again an open circuit.  As I was staring at the newly failed stator plate I noticed scuff marks on the insides of the coil frames where they surround the rotor.  I thought that was odd so I removed the plate and noticed that the rotor itself had scuff marks all around its circumference.  I put two and two together and surmised that the rotor had been scuffing against the stator coil frames and that this vibration must have caused the coils to fail.  At that point I grabbed a hold of the rotor on the end of the crankshaft and tried to move it up and down.  Low and behold there was a lot of free play and some clunking.  The outer bearing on the crank shaft had failed.  Bottom line, back to Suzuki for outer bearings and seals for the crank on both sides along with another stator assembly.  Bike ran like a top after I put it back together.

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I had a stator fail on my 1978 RM-125.  Was out riding it one day and all of a sudden it died.  I must have kicked it a thousand times and nothing.  I pushed it all the way back to the truck, about two miles and fairly level so not too bad.  Sat around pondering what could be wrong for another hour or so and on a whim tried to start it again. If fired right up so back to riding I went.  It only lasted about 15 minutes and then it died again.  Pushed it back to the truck again, loaded up and headed for home.  Stopped by the Suzuki shop the next week and described what had happened.  They recommended that I check the resistance (continuity)  of the stator coils and told me how to do it.  So I went home, got the ohm meter out and started measuring.  Sure enough I had an open circuit.  I went back to the Suzuki shop and ordered a new stator assembly, not even considering what might have caused the original to open circuit.  I got the new part a couple of weeks later and installed it on the bike.  I kicked it over and it fired right up so I loaded it up in the truck and went out to ride.  After about an hour or so of riding the darn thing quit again.  I packed it up and went home.  This time I knew how to check the stator resistance and I did.  Again an open circuit.  As I was staring at the newly failed stator plate I noticed scuff marks on the insides of the coil frames where they surround the rotor.  I thought that was odd so I removed the plate and noticed that the rotor itself had scuff marks all around its circumference.  I put two and two together and surmised that the rotor had been scuffing against the stator coil frames and that this vibration must have caused the coils to fail.  At that point I grabbed a hold of the rotor on the end of the crankshaft and tried to move it up and down.  Low and behold there was a lot of free play and some clunking.  The outer bearing on the crank shaft had failed.  Bottom line, back to Suzuki for outer bearings and seals for the crank on both sides along with another stator assembly.  Bike ran like a top after I put it back together.

Thank you, you probably saved me from the Same situation, tearing into tonight, I'll let you know what I find

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Pulled stator, actually looked new/newer, had it checked and it was fine! Coil had some funky wiring! Hoping this is the issue, when it was running it runs phenomenally! Any other suggestions!

Thanks guys!

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You can take my advice with a grain of salt because it might not be relevant in your case but I have seen alot of coils that you can unscrew the cable between the spark plug cap. There is a screw at the bottom that threads into the wire core and that's how it makes contact. With time this contact becomes eroded and If you just unscrew the cable, the cut the cable ends just a 1/4 inch on each side and thread it back in. Some coils work like that, some don't, it may be worth checking... I'll bet hundreds of perfectly good coils ended up in the parts bin because of bad wire contact.

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If you have a system that uses the "screw in" contact method this will work perfectly.  I don't remember how to determine non-destructively if the screw in type of plug cap is used or not.

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Going out on a limb here if something gets sucked from the tank into your carb and partially or completely blocks your slow jet it will make it difficult to start. 

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