We are nearly complete reassembling our 2009 Yamaha XT250. The bike as delivered to us never quite ran right and the seller was anxious to get rid of it – he said he had cleaned the carb and gone through everything. When we got the bike it would run okay for a few minutes. Once warmed up, the engine start to stumble and bog under anything more than 1/4 throttle. It was cutting out so bad it sounded like it had a rev limiter at 3,000 rpm. However, all of the electrical tests checked out fine. The machine had very low miles and looked brand new. There were no indications of a mechanical problem. CYCLEPEDIA’s experienced technician was confident it was a rich running condition that was causing the problem.
We cleaned the carb and discovered the previous owner had taken a drill to it – apparently he thought he was removing a brass plug to reveal the air screw but it turned out he drilled a whole through the carb heater base and damaged the carb in a way that was creating a rich running condition. We attempted to fill the drilled material and eliminate the carb heater but the same rich running condition persisted.
To confirm our damaged carb theory we swapped out the carburetor for a known good unit from our Kawasaki KL250 Super Sherpa. Low and behold the bike runs great. We checked with MR Cycles and a replacement carb is almost $300. There doesn’t seem to be enough room to fit a flat slide carb and used carbs for this model are not widely available so it looks like we have to bite the bullet and purchase a new carb. At least we have diagnosed the problem and should have this bike running like new again. Take a moment to look before you drill your carb, the original owner of this bike was well meaning but it ended up costing him a lot of money in the end. If he had used a CYCLEPEDIA Online Service Manual this shiny new dual sport would still run correctly.