yeah - this is exactly what's happening to me. I can start it from cold, but warm is another beast. It seems to almost start after every other kick but isn't quite catching... but I'm afraid to give it too much gas. After several failed attempts, I will use the electric start, but even then it turns for a bit before it starts.
Well it's been about a year since my last post on this rat bike, and since then I've had a blast racking up about 6k miles on it! I'm only left with a couple mysteries I'm still trying to figure out. To recap:
-Newly rebuilt "shovelution" with an S&S complete bottom end, hydraulic kit, etc.
-Original cylinders and heads. (1200cc with standard compression).
-Single fire coil with Compufire ignition.
-Pipes have baffles, and the breadbox air filter is using oiled foam.
-64 main jet, .295 intermediate (super E carb)
-only use 91 octane non-ethanol
The main issue I'm having is the bike occasionally "diesels" when I shut it down. I'd say 1 in 3 shut downs, it will stumble. I know this could be timing, or a lean condition. Yesterday I realized my mixture screw was more than 3 full turns out, so I went up to a .031 intermediate, and it's like nothing changed, I am still more than 2.5 turns out for the right idle mixture.
To me, the 64 main jets seems small compared to what other guys are using, but anything larger and the bike starts to warble at high RPM's. (I'm still not sure if this could be the rev limiter, but it got much better with the smaller main jet).
I am also on the least agressive curve on the Compufire ignition. Anything more and the bike starts to ping a tad.
Eventually I will figure this out, but I'm wondering if I'm chasing my tail and should try another ignition, even though the Compufire kick start seems work great. Last year we tried the Ultimate dual fire, but it would only run on once cylinder not matter what we tried, so I went back to Compufire.
64 on the main jet does seem small.. Normally a 74" motor would run a 0.028 or a 295 with the S&S E.. I'm pretty sure with the Compu-gire ignition that you have has a mechanical advance under there.. I ran one on my '77 and it worked great.. To me it sounds like mechanical advance is sticking.. it'll give you the run-on when trying to shut it off because he advance is staying full.. check the weights and springs to make sure they're not worn.. Make sure the shafts for the weights are not worn and the springs are nice and tight and it's working the way it should be..
Last edited by 98hotrodfatboy; 10-13-2024 at 06:05 PM.
I agree on those jets - not sure why the bike likes such a low main...
That compu fire ignition is all electronic - there is no mechanical advance. My previous ignition (Dyna) had the mechanical advance, which was a nightmare. John (from this forum) helped me fix that with a better spring mechanism and it was much better, but I ended up going back to a fully electronic.
Those banana calipers are probably the worst brakes I've ever experienced, but I really wanted them on this build because it's all part of that era. The drum brakes on my 1942 WL work twice as good!
10-04-2023 | 04:35 PM
