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74 MT 250 elsinore Diesieling? HIGH RPM

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ok where to start, i bought a honda elsinore MT250, it didnt run all that well so i bought a carb rebuild kit. so i rebuilt the carb and it will not run without the choke on, it seems not to responde to needle changes as well. i rode it around the block to try and clean it out. it statred really smoky. after about a 1/4mile ride when i returned the throttle back to closed position the motor didnt seem to wind down instantly, so it seems that it is running too lean. I went back to the garage started the bike after 10 min of kicking it finally fired ran for 10 -15 sec the the motor rpm's shot up super high. i mean crazy high so i turned the kill switch, nothing pulled the spark plug wire, nothing still running (this is my first experience w a motor running with no plug wire so i am freaking out.) finally i pull the fuel line after 20 sec it dies. whew. I noticed this morning that the trans has no more oil in it, is there a possibility that some of the smoke commig out of the motor was trans oil due to bad crank seals?

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I had a similar experience with my friend's MT250 when I ran the carb dry before putting the bike away. The carb had been running really rich and the idle speed screw was set high, and after idling for a few minutes the rpm shot up to redline and stayed there. Luckily, the kill switch worked OK.

If you ever have that dieseling experience again, I'd jump on the bike, shift it into 2nd, and let out the clutch with the front brake on; better a little clutch wear than the motor turning 12 grand. :thumbsup: It can be kind of hard to remember what to do when all hell's breaking loose, though.

Try refilling the gearbox and see if you get smoke. If not, something probably went wrong during the carb rebuild; plugged jet(s), incorrect float level, leaking gasket/manifold, etc. I'd replace the LH crank seal too.

If you DO get smoke which goes away when you lean the bike way over to the left, that's almost certainly a bad RH crank seal, and a big repair job.

Ray

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I noticed this morning that the trans has no more oil in it, is there a possibility that some of the smoke commig out of the motor was trans oil due to bad crank seals?

explains all of your issues.

massive air leak and its burning the trans oil.

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