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Posted

So when i do eventually get it to start it wont idle, The choke does not help it start and when it is running if you pull the choke or fuel enrichment lever down it stalls out, im at a loss i have rebuild the carb checked the pump, checked spark, voltage, and even cleaned my tank. The fuel pet cock is non vacume and brand new. Any ideas Please?

  • 3 weeks later...
Posted

Hate to be the bearer of bad news, but my LT 250 Sport was doing the same thing...wound up being the CDI box was getting weak...finally progressed to the point of a no start condition no matter what I did.

Took one off of an old Kawasaki 4 stroke  motorcycle frame, did some research to find out the pin assignments on the connector, married the functions up to the same functions of the Yamaha wiring connector...now runs fine and starts easier than it ever has.(which is a blessing because the Sport 250 is a side kick which is hard to use from jump street.)

Posted

The early 250's & 300's were plagued by soft intake valves. Likely that the valve clearance has gone away. I believe the clearance is supposed to be .002" on Int & .003" on Exh. I always set them both to .004". It will start easier with very little increase in valve noise. Of course, the problem could be in the carb, but since these are known for the valve problem, take the time to set valves. Side notes here are 1) be sure to check the air filter - dirt getting past it will destroy the intake valve (as well as the piston & rings), 2) there is only so much valve adjustment available before the valve has to be replaced, and 3) I would do a cranking pressure test before and after adjusting valves - GOOD readings are @ 150 psi, while under 100 psi, it will not want to run - if adjusting valves doesn't bring it up in a good range- suspect bad valves and/or rings.

Dr. Dave

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