Motorcycle Repair: 1985 xt 250 m, air vent, xt 250

Question
my bike runs good for a while, when all of a sudden it laggs and some times quits as if there was a starve for either oxygen or gas, however i've clean the oil and air filter, cleaned the tank (replaced with new gas) and still somethings not right. could it be ignition or even a tweak in the carb?? please help, summer is soo close!

Answer
Hi there,

have you checked that the air vent of the fuel tank in the filler cap is not obstructed? This could prevent the fuel to flow after some times with the engine running. Then as the bike slows down the fuel request becomes low, the air pass in the tank as it can, often by the lack of tightness of the filler cap gasket and the engine runs well again for a while and so on. Its quite a common failure.

Hope this helps!