Engine runs terrible when cold, great when warmed up

• Nov 22, 2019

• #41

Sweet5ltr

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Kern Dog, you may want to install an electric inline pump. Will help prime & fill the bowls. This is 90% of the battle starting a carbureted application if it typically sits for long periods of time. Don't worry too much about AFR, 13.5 is fine at idle if that's what the engine wants. It's good practice to set the idle AFR when at operating temp. Most likely it was just bad gas.. that would have been my first change, fresh fuel. What's your cruise AFR?

 

Last edited: Nov 22, 2019

• Nov 22, 2019

• #42

Kern Dog

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It still runs in the 13s at cruise and fattens up to the low 12s at WOT. Barely any smoke is visible and it "smells" reasonably clean.

 

• Nov 22, 2019

• #43

BB BELLA

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which demon are you running BG or street? I'm not familiar with either,just wondered when you said you emptied float bowls and retried it with fresh fuel if you have to fill float bowl first like a holley so you don't damage carb with backfire, guess im realy asking do they have a powervalve?

 

• Nov 22, 2019

• #44

Sweet5ltr

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Kern Dog said:

It still runs in the 13s at cruise and fattens up to the low 12s at WOT. Barely any smoke is visible and it "smells" reasonably clean.

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That's about all you can ask of it, seems like it's tuned fairly well. You can lean it out at cruise to 14-14.5 but really, it won't save that much fuel. AFR @ idle could also be leaned out, but if the plugs look good [let it idle @ operating temp and shut it off] then I wouldn't worry about it.

 

• Nov 22, 2019

• #45

Kern Dog

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BB BELLA said:

which demon are you running BG or street? I'm not familiar with either,just wondered when you said you emptied float bowls and retried it with fresh fuel if you have to fill float bowl first like a holley so you don't damage carb with backfire, guess im realy asking do they have a powervalve?

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I can't recall the exact model. I think it was called the Speed Demon. It is a vacuum secondary, electric choke with the internals very much like a Holley. Jets, metering blocks, power valves, needle valves are all interchangeable.