Revs on the way back to idle

[jcongerton]

Hi,

My engine (picco p7r) which seems to be tuned quite well, runs around 220 - 230 mark with good smoke at wot and good accelleration seems to hang in the high rev zone when returning from WOT to idle (even when applying brakes). I have checked the carb movement to ensure it is returning to the idle position ok, it is. My first thought is that my LSN is to lean? I got car upto temp and pinched the fuel line, lasts aroud 6 - 8 seconds before dying, which i think is right. Tested for air leaks in the carb, fuel hoses are correct length. Anyone know what to do next??

Thank you

Jason

 

[redhatman]

the only thing I could say is check for air leaks... you said you already tried that, but seal it anyway. When you have the air leaks, it is an inconsistant idle, which could cause throttle blips to make it go, while in idle.

 

[Diver6127]

I would check for any binding in your linkage. If there is, loosen the retaining screw that hold the carb in place and get a more straight shot in the movement of the arm. IF this is a brand new engine or still under one gallon, that coult be the culprit as well.

It takes up to a gallon for these engines to break in. I experienced this in both of my novabased engines. It'll get better as the engine runs through more fuel. Try blipping the throttle slightly and see if it comes down. Otherwise, check the linkage as well as check for airleaks. BUT, if there is an airleak, your engine will overheat at idle and your idle will be either erratic or nonexistant (your revs will soar in a heartbeat).

 

[jcongerton]

Thanks for your replys, the engine is new. This is the first time i have realy run it a good temps, used the heat cycle break-in (to the letter), linkage looks fine and is in line with carb and servo, no air leaks in this sucker, i sealed any way! The car idles fine, if i WOT the car towards me hit the breaks, the engine will rev through the breaking process and return to idle about one second after stopping. I notice my car will idle for a long time, and still pull away quite quickly without bogging down could this be a factor? Or its hopefully like you said diver6172, that its due to new engine - fingers crossed!!

 

[Diver6127]

thay's what it most probably is. On my Novarossi NS12S3 as well as my Mugen X12-3port, they both did it. After about 1 gallon of fuel, it was gone. Drops straight down to idle.

 

[redhatman]

yea, some engines can take a while before they are fully broken in. Just run it more, and if the problem persists, then tell us.

 

[Diver6127]

On these novabased engines, they won't "wake up till about 3/4 or 1 gallon of fuel.

 

[jcongerton]

cool thanks for you help

 

[olds97_lss]

You might want to richen the high needle a little. It might help some.

I know when I'm edging lean on the high or low that it "winds" down a bit when I let off from WOT. If I richen the HSN, it typically drops almost instantly.