Popping on Decel

970 Views 5 Replies 3 Participants Last post by miller, Sep 19, 2008

formervetman

Discussion Starter · Sep 19, 2008

I've been running a 190 main and a 50 pilot with the needle in stock position?? and the fuel screw out probably a little over 3 turns, maybe 3.25
It was running fine like this except it seemed if my air filter got dirty at all I would get a slight high rpm cut out, so I thought I may be a little rich.
After a build, the shop owner said 190 is way rich, try a 168 and 2.5 turns out on the fuel screw. Well that's when I got allot of popping on decceleration.

So I put my 190 back in and went to about 3 turns out on the fuel screw, seems fine again, although may want to slightly pop on decel.
Right now I'm just breaking her in after a build so I am not getting on it hard enough to see if it will pop more.

But would you guys think with a 190 main that I would be on the lean side?

Since I had to keep my air filter clean, so I would not get the high RPM bog that I may be a liitle rich?

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very_fast_450

· #2 · Sep 19, 2008

popping on decel is an indication that the pilot is too lean.... a clean filter on decel will permit more air-flow; thus causing a leaner condition to occur.

popping on decel isn't developed from the main circuit.

I hope this helps. Good luck with your tuning.

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formervetman

Discussion Starter · #3 · Sep 19, 2008

popping on decel is an indication that the pilot is too lean.... a clean filter on decel will permit more air-flow; thus causing a leaner condition to occur.

popping on decel isn't developed from the main circuit.

I hope this helps. Good luck with your tuning.[/b]

Thanks for the info.
So your thinking I should go up on the pilot? What pilot? Would that let me screw in my fuel screw slightly?

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miller

· #4 · Sep 19, 2008

yes, to richen , go out on the screw or up in size on the pilot.... put the 168 back in if your builder suggested it, its sounds right and like he said it wont cause popping on decel

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formervetman

Discussion Starter · #5 · Sep 19, 2008

out on the screw or up in size on the pilot.... put the 168 back in if your builder suggested it, its sounds right and like he said it wont cause popping on decel[/b]

So I got the popping on decel from turning the fuel screw in 3/4 of a turn and not from putting in the 168 main? Because I did them both at the same time and that's when I got the popping.

What size pilot?

This is a new builder and when I got my motor back the valves were so tight I could hardly kick her over. I had to readjust my exhaust valves.
So that made me a little skeptical of his jetting suggestion.
You think 168 seems about right with the mods in my sig.

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miller

· #6 · Sep 19, 2008

i think it would be fine...JMO if it was popping you could go to 3 turns out or a hair more... i bet a 50 or 52 is plenty on the pilot.....

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