by bgsengine » Thu Nov 21, 2019 11:09 am
crankcase "compression" meaning the pressure/vacuum pulse caused by movement of the piston. This positive/negative pulse pressure is what is used to operate the carburetor's fuel pump diaphragm. It MUST be air tight or those small pulses bleed off. AND, the crankcase must also be air tight (and vacuum tight) because otherwise it will suck in unmetered air that mixes with the fuel charge and causes lean fuel mixtures. Did you try putting a small charge of gas into spark plug hole? (less than a teaspoon) and see if it will fire that charge? if it will, then the fuel that you are introducing through carburetor is not getting to the engine properly, which is why Sky asked if crankcase pressure had been verified. Did you use all new gaskets on assembly? how far was it disassembled? even the tiniest scratch on a gasket surface can lead to a vacuum or pressure leak, as can hardened or failing crank seals. A pressure/vacuum tester would be a MUST-HAVE investment for anyone that works on 2-strokes regularly, along with the know-how to perform the leakage tests.
How poor are they who have not patience. What wound did ever heal, but by degrees? - Iago (Othello Act II, Scene 3)