18 HP no spark

[Billhein94]

I have a 1973 18HP model 18304A that I took apart for parts and now I am thinking about putting it back together and see if I can get it running. I did a compression test and have 100 on both cylinders, but I can not get any spark on either cylinder. I took the fly wheel off and re-gapped the points and everything looked really good up there. It had electric start and the harness to go with, but I took that off for another motor, so the little connectors that go to the kill switch are not connected to anything at the moment. If I remember, the kill switch is normally open and you "short" it to kill the engine, so not having them connected shouldn't effect spark...right? I feel like I am missing something simple. Could both coils be bad? I have never had this running...these are my preliminary checks before I decide to keep going or use it for parts. I have a mulitimeter, just not sure what to check and what readings I should get. I also have 2 known good coils in another motor, but I just got that one back together and really don't want to take that apart again.

 

[racerone]

Both point sets must be absolutely clean.

 

[Billhein94]

everything looked practically brand new when I had the flywheel off.

 

[timguy]

The kill wires go to the points, when shorted to ground....or together, you will defeat the spark. Did you look to see if the coils have any hairline cracks? They will arc to ground, sometimes in a hard to see location. A removal and exam will reveal any arcing. As Racer states, double check points for continuity with your multi meter. Any resistance will destroy the chance of a spark.

 

[Billhein94]

would I just meter continuity through the points when closed?

 

[timguy]

Right, then exercise them with meter on, condenser disconnected. I take a little probe, like a tiny flat blade screwdriver and open and close the points.

 

[fdrgator]

With wires disconnected ohms across the points should be zero when closed, infinity when open. Not an ohm or two, but zero. If your meter is capable of reading very low resistance, with wires connected should be zero when closed, and somewhere around an ohm when open.

 

[timguy]

Right. Now if the cam wick is dried up, decomposed, or missing, you can put a tiny dab of high quality grease, (I use Amsoil synthetic red), using a toothpick or similar, to the leading edge of each cam follower. Lasts for years and years. Remember the pre electronic ignition automotive distributors? That's all we did! And on a 4 stroke V8, the points are REALLY working, four bumps with each crankshaft revolution....so....why not?