1980 4HP JOHNSON SEAHORSE BACKFIRE

JOHN BLUESY

Cadet
Joined
Jan 23, 2021
Messages
9
Can anyone tell me whats wrong, The best response I can get is a backfire, The motor was seized, so I stripped it and freed up the pistons and put it back together, no gearbox on it just to get it to fire up. I set the points at 2.0 at the o in TOP mark on the point cam, I cant see how it could be 180 out and I tried the plug leads both ways to get the same backfire, The bottom plate beneath the magneto was a task to line up and I only got 3 screws in, but I cant see how the bottom swivel plate would affect timing, the flywheel has 2 cut marks underneath which I assume are timing marks but cant be seen with the magneto on. Should the motor run without the gearbox fitted or does it need back pressure ? There is two line marks on the magneto bottom case but they dont align with the magneto mark, the crank key only allows the magneto go in one position, Weird just cant get it to do anything except backfire, compression 75 psi both cylinders, new plugs, tried squirting a bit of gas in the plug holes, tried squirting the carby, tried every throttle position, spark seems to be plenty good enough, blue. How is it possible for the timing to be out. The head only seemed to go on one way and the pistons only seem to go in one way or they hit the head, Got me stumped.
Picture if the motor type attached
 

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