mikuni question

[mieltje]

converted my 2004 heritage from efi to HSR 42 carb last year with an ignition amm-p3 , all works great , but still cant get rid of a small "backfire in carb" problem . When on idle , opening the trothle smootly , there is no problem .. when opening very fast , i often recieve a backfire in the carb and the engine stops running . I checked on air leaks and didnt found any , turned in and out both screws of the acceleration pump but that didnt change ... been told thats a carb problem but dunno what else to do .

configuration :

mikuni hsr 42
kuryakyn hypercharger airfilter
supertrapp cross over exhaust

[fxr4mikey]

does your carb have the stock iddle jet and the stock jet needle ?

Have you tried a one size richer iddle jet, and/or a one size richer jet needle ?

Have you tired to raise the jet needle one notch ?
Raising the jet needle will get the tappered part of the needle in the open position 'sooner' = a bit richer.


I had a very similar problem with mine. I put a one size richer idle jet, and jet needle in.
Started it up, warmed it up, readjusted the idle screw. Before this the idle screw was set at just one turn out from the bottom. Now she idles at just past two full turns out from the bottom.

I no longer have that stumble problem just off idle.

Good luck !

Let us know what you find out !!

[blkfalc4]

Out the carb signifies that it's too lean,,,richen her up.

[mieltje]

thanks for the information , will start with raising up the jet needle one notch ... if that doesnt work , will go for a richer jet ( 96 ) and yes the carb is still stock , no changements been done .