Motorcycle Repair: atv, fuel stabilizer, kinds of varnish

Question
Hi, I have a fairly generic question, its regarding a yamaha 350 single cylinder engine. it was running fine until parked. It sat up for a while, and now wont start. It is firing, and i sprayed starter fluid directly into the intake while turning over. it just spins over, but when i hold my hand over the muffler it starts to hit like it wonts to start, but thats the most I can get it to do. My guess is that it doesnt have enough compression, would that sound right to you? thanks for any info

Answer
Jerry, you didn't state the length of the machine being "parked," but if it was over a month and you left old gas in the carburetor, then the idle jet is plugged up and bikes don't start well or idle until the jet is cleared. Evaporated gasoline leaves all kinds of varnish and other deposits within air and fuel circuits. Best to remove and clean the carburetor (or have an expert do it), then always remember to use fuel stabilizer in the gas and drain the carburetor when the vehicle is going into slumber for more than a few weeks.

Bill Silver