jasper

I have an N-reg Yamaha TRX with a rather bizarre carb problem. Basically I stored it over the winter, had it running in the garage once to charge up the battery, and then on the first ride a few months ago, noticed that at 3/4 throttle, if you opened the throttle to full, the bike died completely. However, rolling back the throttle gently allowed the bike to run ok again. It was fine before the winter, so what could have changed? It sounds like a main jet issue but it was running fine before I put it away. Anyone got any ideas or had a similar problem? Jasper