1971 Johnson 40 hp 40el71g no spark top cylinder

[kaneerarchery]

I have a 1971 Johnson 40 hp (40el71g). I recently bought this motor cheap because it had no spark on either cylinder. The previous owner could not get the flywheel off. I checked the compression before buying and it had about 95 psi in both cylinders. I pulled the flywheel and using information from this forum checked the coils with a multimeter. One coil was bad. I replaced the bad coil, installed and gapped 2 new sets of points, installed two new condensors, and replaced both plug wires and plugs. I lined each coil up with the machined boss on the magneto for the air gap. I installed and torqued the flywheel with key. When I check for spark using a spark plug tester, I get a bright white-blue spark on the bottom plug and no spark at all on the top plug. I have not pulled the flywheel back off yet so I will have to check if the top cylinder plug is attached to the old coil. Did I get a bad condensor? Is the other coil bad? Any help would be appreciated. Thanks kaneerarchery

 

[kbait]

Re: 1971 Johnson 40 hp 40el71g no spark top cylinder

Did you gap each set of points at their widest opening point on the cam? You have to turn the motor 180 degrees after you've done the first set. If the old coil has any cracks, it's toast and needs replacing.. even if it tests out on the multimeter as it will arc to ground under load. Good luck!

 

[kaneerarchery]

Re: 1971 Johnson 40 hp 40el71g no spark top cylinder

I will pull the flywheel today after work and re-check the points. I did rotate the crank and set each set of points where I thought was their point of maximum gap. I also need to see which coil is attached to the top plug. I will replace it, if it is the old coil that was not already replaced. I once bought a condensor that was bad for my 1970 Jeep. Are the new ignition parts like condensors dependable. Thanks.

 

[kbait]

Re: 1971 Johnson 40 hp 40el71g no spark top cylinder

The forward mounted coil should be connected to the top plug. I've heard of condensers being dead on arrival.. You could just switch 'em over and do another spark test (no need to fully tighten the flywheel nut.. just firm).

 

[F_R]

Re: 1971 Johnson 40 hp 40el71g no spark top cylinder

Put that multimeter to good use and check those new points. The resistance must be zero ohms when closed. Not one ohm, or half an ohm, zero ohms. When open, around an ohm.

The coil toward the front is the top one.

 

[kaneerarchery]

Re: 1971 Johnson 40 hp 40el71g no spark top cylinder

I replaced the second coil. On second inspection it had a thin crack. I re-checked the point gap, installed and torqued the flywheel. I had a good spark on both plugs. I put a trash barrel under the foot, filled it up with water. I cranked it up with the pull cord. it took about 5 pulls but it cranked up. Motor runs great. Thanks for the help.