Motorcycle Repair: xr 80 r, air fuel ratio, xr80r

Question
i have a 1986 xr80r it has sat for one year. i recently pulled it out i cleaned the tank and carb replaced the fuel line and replaced the plug. im getting fuel and spark but it will not start it only back fires what should i do

Answer
Donnie, there could be a number of things causing this problem.  Does the engine have good compression?  It should have somewhere around 140-160 psi compression. Assuming that's good, you may have too much fuel getting into the cylinder or too little. A overly rich air fuel ratio will foul the plug and too lean of a mixture won't ignite.  It's got spark or it wouldn't backfire in the exhaust.  It's possible the spark timing is off.  You just have to check each system and find out which one is out of spec.

Regards
Rich