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Sporadic miss cold and hot
Sporadic miss cold and hot
Magneto ignition with fresh coil
Rocky point ignition switch
12v system with "lathed" 1980's airhead rotor and stator with under-tank regulator.
Harms points plate.
Everything but crank and heads done by your truly since it was built from a frame and 15 boxes of parts in 2005 era.
That gives the background. I know the bike well. Have had it titled in 5 states now. Runs well.
One gremlin I can't solve is a sporadic miss.
When it's freshly started and idling low and cold, about every 10 seconds and sometimes not at all it'll miss a fire. It slows down for a sec and returns to normal.
Then when I'm riding, and also sporadically, if I'm too low rpm in a gear or heading up a hill in too low, it'll stumble similarly. Just 1 miss. Like red October "give me a ping Vasili, one ping only please."
The 2nd scenario makes me think carbs.
The idling scenario makes me think spark or timing.
My advance puts out a single image under a timing light. Have that merit badge.
Timing works to spec from OT to S.
Valves are right, carbs are right.
My next thought is to put my spare set of carbs on with a fresh rebuild of all the carb guts, new plugs and wires, points, condenser, coil, etc. And just start elimination of options but before I create so many backup spares, I'd love to hear if anyone has any experience with something like this.
Thank you
- Micha
- Posts: 768
- Joined: Fri Oct 12, 2007 2:24 am
- Location: Israel
- Has thanked: 11 times
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Re: Sporadic miss cold and hot
I don't know specifically about the problem you describe, because as mentioned it can have many reasons, but checking the carbs for tightness is simple:
During idle rpm, brush engine oil on the carb's body, on it's connection to the engine head (flange) and to the air intake (at the pipe connection).
If you hear a change in the sound of the engine you will know where to look for a leak.
R51/3 1952
Engine Nr. 529466
- VintageJim
- Posts: 105
- Joined: Thu Oct 07, 2021 2:07 pm
- Location: Arizona
- Been thanked: 3 times
Re: Sporadic miss cold and hot
Jim
Re: Sporadic miss cold and hot
Charlie.
Re: Sporadic miss cold and hot
I feared it would be a brute force "check everything" scenario but was hoping for a telltale sign I wasn't aware of.
I'll start with cheap and easy and go down the line.
Systematic isolation of variables.
Experience says it'll be something dumb.
I'll report back when discovered.