Motorcycle Repair: XL250R Engines Dies, fuel drain, spark tester

Question
I am experiencing my engines dies after about 5 minutes of riding.  I immediately thought it was a fuel problem and did the following< checked the gas, cleaned and checked the in tank fuel screen, pulled the carb and replaced the float and needled and cleaned all components.  After doing this, it again die on me.  It does a couple of backfires, then starts to sputter, working the throttle buys me a minute or two more riding time, then dies completely.  I jumped off the bike after it die and check the fuel drain valve on the carb and gas did come out.  I put an in line spark tester on the bike and it had good spark until the engine die.  Could it be a valve issue?/

vr
Grant

Answer
Grant, the valve clearances are only .003"- .004" in/exhaust, I think. If they are tight, the motor will start then sputter as it warms up.

Make sure that the gas cap is venting properly. Backfiring as you mention sounds like it is fuel starving. How much fuel comes out when the bowl drain is opened?

Bill Silver