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Andrew: Im thinking similar to Duane, you could have (B) a valve problem ORRRRR RRR (A) the mag is out of time!!!!! HOWEVER that part about "it will run if it fires up" kinda rules out a major mag problem like wires reversed etc but I already typed it all before I re read the question lol, but its good info anyway which may help in the future. Im outa here, gonan be late for an auction,,,,, ,,,,, ,, (A) I wish we knew what mag you have, since as Duane said the direct drive non reduction gear mags like the Wico C and X fire on BOTH TDC's, the Compression and Exhaust, while the reduction gear drive 1/2 speed mags like the Wico AP and some of the Fairbanks Morse only fire on the Compression stroke TDC. On the Wico C and X if the wires are reversed she may pop n bang n backfire and/or kick the flywheels back, but a simple wire reversal makes them run. NOT so on a reduction gear mag. If out of time or wires are reversed, she could pop n bang n backfire etc etc which a wire reversal will NOT fix. Pull the plugs for easy flywheel cranking and:::::::::: Bring the left piston up to TDC on its Compression Stroke. That will be when shes building compression/presure out the plug hole, cuz if on the Exhaust stroke, it wont cuz the exhaust valve is open ::::::::: Then when coming up on the Left Cylinders Compression (NOT Exhaust) stroke, when the Flywheels Left Hand Impulse (LHI) mark passes by the flat mark on the tractors side at 3 o clock, the mag snaps AND FIRES THE PLUG GOING TO THE LEFT CYLINDER. They were originally wired top cap tower to left on the Wico's::::::::: Next, see if 180 of flywheel rotation later (Flywheels LHI at 9 o clock) she snaps again and the plug wire to the right cylinder fires????? ??? SHE HAS TO DO THAT TO RUN REGARDLESS WHAT MAG IT HAS!!!!! !!!!! !! Regardless if a direct or reduction gear mag, it will snap n fire at the Left then 180 degrees later the Right cylinders Compression TDC, but the reduction mags will NOT fire on the Exhaust TDC's. Thats one way to tell the difference. The reason for telling all this is so you can tell what type of mag you have and to verify shes firing the correct cylinder at the correct TDC. If its direct it makes no difference (fires at BOTH) but you still need the correct wire to the correct cylinder,,,,, while in the reduction mags it has to be the correct cylinder and at the right time and a wire reversal will NOT fix it. OTHER TIMING ISSUES If the flywheels on the correct crankshaft spline??? and the crank to cam and cam to governor gears are ALLLLL in time??? at the left cylinders TDC the Flywheels LHI should be at 3 o clock and the female drive slot in the governor shaft (where mag fits) should be flat horizontal fore n aft. Make sure the left cylinders plug wire is firing on its compression stroke TDC (LHI passes by 3 o clock) and the right cylinders plug fires 180 later when its on its Compresion TDC (Rememebr, the Wico C and X will repeat that even on the Exhaust TDC's), and if thats so Im no longer suspecting a mag problem REGARDLESS of what mag you have. (B) Remove the valve covers and insure ALL valves open n close and there is at least some valve lash. Disconnect the plug wires so she dont fire and bring the left cylinder up to TDC on its compression stroke and stop near TDC and LISTEN CAREFULLY for presure escaping out the carb (bad intake valve) or out the Exhaust pipe (bad Exhaust valve) or the ctrankcase (ring blow by). Thats not as good as a compression or leak down test Duane mentioned, but the physical observation to insure the valves at least opening n closing and theres some lash coupled with the listening test ought to give you some idea of a problem if the mags timing checks out okay. Thats all I have to say about that, Im headed for an auction, let us know what you find, good luck n God Bless John T
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