"Motor needs three things to r
"Motor needs three things to run
1) compression - low compression can cause bad idle, poor top end performance, stalling etc - it's the first and easiest thing to check
2) spark - no spark, no run - if you have strong spark at all plugs that tells you that every component of the ignition system is working as it should be - again, it's a simple test.
3) fuel - sometimes the most difficult to troubleshoot - could be anything from cooties on the pick-up in the gas tank right the way through to the carb(s), reeds or a bad crankcase seal.
So it's imperative that you test the easy stuff first, instead of chasing your tail only to find later that (after rebuilding carbs, replacing fuel lines etc) that you have no compression in the number 2 cylinder..."