1989 50hp vro Johnson misfiring on one cylinder

" Can anyone help? I have rece

" Can anyone help? I have recently bought this engine (cheapish) knowing that there was a misfire problem. I thought I would start replacing parts as I am no expert to try by a process of elimination to solve the problem. Before I do, I would like to know if this is a common problem on this model and if so, what can be done about it? Model no. AJ50TLCEC. It runs relatively well with the warm up handle well open but falters and dies as I close it. Thanks. "

"Bill.... Regardless of what p

"Bill.... Regardless of what problem one might have, always check the compression before going any further. It should be in the 100+ psi range and even on all cylinders.

With the spark plugs removed, check the spark on both cylinders. It should jump a 7/16" gap with a strong blue flame on both cylinders. If you have no spark tester, you can insert a philips screwdriver of the proper size into the rubber s/plug boot, then hold it approximately 7/16" away from the powerhead.

You've indicated that you have poor spark on one cylinder. Notice the primary (orange) wires leading to the coils. Switch the orange leads so that the orange lead that was associated with the good firing coil, is now connected to the coil that wasn't firing. Crank the engine and observe the coil. If it still isn't firing, obviously the coil is bad. If it now fires, the coil is okay and the problem lies elsewhere.

The s/plugs should be Champion QL77JC4 or L77JC4 plugs set at .040 . Let me know what you find.

Joe "

Joe
Thanks for advice. The

Joe
Thanks for advice. The compression is about 125 on both cylinders so looks ok. I tried checking the spark with a screwdriver in the ht leads but not very easy as engine rattles so much when cranked over. Dont have a spark tester but got one on order so will try with that when I get it. I'll let you know.
Thanks again.
Bill