Compression test ? if the carbs fueling up but its not getting to the cylinder its either blocked up main jet/idle jet, Or there is no compression and the motor is unable to create a vacuum to draw the fuel into the cylinder. the motor when running in its cycle will create a vacuum usually on the upstroke allowing a fresh charge of fuel to enter the crank/cylinder ready for compression and ignition. lack of this vacuum means motor cannot get fuel in. places to look are piston ring failure / crankshaft seal failures / head/cylinder gasket failures
