Delcolight "stopping" problem solved!

It's been a long time since I posted on here, and my apologies for that. Some might remember the mysterious problem I was having with my Delcolight 850. A fresh rebuild including rings, valves, mucking out the crankcase, winding a new cutout coil........quite a project!

Came the big test day and the thing wouldn't run for more than ten minutes, then mysteriously stopped. During its run the speed was high, the charging around 20 amps and it vibrated like mad. I tried everything I could think of or dream up. Were my new valves leaking? Ignition trouble? (I installed a Volkswagen coil due to the original being open) My wiring? Fuel delivery problem?

I got disgusted and it sat for at least two years, although I was careful to keep my new 8 volt golf cart batteries charged. Today I tried it again and noticed that with the air control (choke) set in the run position, the engine ran fast and vibrated. So I shut the air down a bit (choked it) and it suddenly smoothed out, stopped vibrating and chugged away with the ammeter showing an 8 volt charge.....for TWENTY MINUTES without skipping a beat and no smoke. I should also mention that I'm at 4000'+ elevation here, so any fuel adjustments have to be played with a bit.......DOH! (best Homer Simpson impersonation)

The fuel "system" on these Delcos is so simple we sometimes complicate it with over thinking. In the previous setting, the engine was apparently running lean ( I had set it to stop any black smoke). This caused overspeeding, vibration and probably some extra heat. At some point engine simply couldn't pick up any more fuel and stopped........then the relay lever would drop. It even says in the manual to set the air control to where the engine runs "smoothly", but never having run a Delco before, what is "smoothly"?

To recap, after starting adjust the air shutter by listening to the rpm and watching the ammeter. High speed and high charging rates are NOT what you want!

Update: As soon as I refilled the gas tank, all my previous settings changed, so it's very fuel sensitive. It's still running longer, not shutting down, but there is a definite miss unless the air control is on a lean setting. Then the engine runs without missing, but speeds up so that the entire generator is vibrating. Obviously it has fuel problems, in that the mixture is not regulated enough to provide smooth running. I'm considering installing a spare Briggs and Stratton carburetor, just to see if that smooths things out a bit (no changes made to original parts, so it can be changed back again). Then I'll know which way to proceed from there.
 
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