Carb Popping

[scubaman15]

Once in a while the carb on my new 07 Chopper will pop back ...I have had this happen on the Harley but not quite as often as this machine is there some thing not adjusted correctly ? Also I get a little backfire sometimes when starting while hot ?

 

[Gas Man]

Yep... popping or caughing out the carb lean... drop your bowl and check your jet sizes.... check the how to section...there is some info there on carb and jet swapping...

 

[scubaman15]

Thanks for info ...its brand new with 200miles so far only pulled over once

 

[LamboV12]

I had a major issue with backfire when starting warm.... drove me nuts. Check the nuts that bolt the exhaust to the block. Mine would loosen up, then when you shut down the motor when hot and let it sit for a few minutes, cold (ambiant) air would draw back into the exhaust causing a backfire on the first stroke of the piston on start.

Normally - backfire from carb = lean and backfire from exhaust = rich, but exception to everything.

Also - temp change can change mix conditions. If you dailed in the carb on a warm 80 degree day and now temp is in the 60's... While riding sometimes I find myself adjusting the mix on my carb a 1/4 turn or so. The mix screw does not need a screwdriver and is the big one right on top. Counter clock-wise lets in more fuel = richer and clock-wise less fuel and will make it leaner.

I have Big Radius pipes and and on de-accel get rumble (no popping) - if she starts popping, tweak the mixture screw slightly until the popping goes away. Usually this will get you dailed in about where you need to be.

 

[scubaman15]

Thanks ...will check it . the backfire thing has to go !!!!!!

 

[LamboV12]

It only happens when your in front a large crowd with a lot of people around the bike and you start it, right?

I forget what BDM says, but the S&S shop manual says torque to 18 ft/lbs.

Mine kept going loose because, eventually I found out, the studes in the case kept backing out.

 

[lee]

I had a major issue with backfire when starting warm.... drove me nuts. Check the nuts that bolt the exhaust to the block. Mine would loosen up, then when you shut down the motor when hot and let it sit for a few minutes, cold (ambiant) air would draw back into the exhaust causing a backfire on the first stroke of the piston on start.

Normally - backfire from carb = lean and backfire from exhaust = rich, but exception to everything.

Also - temp change can change mix conditions. If you dailed in the carb on a warm 80 degree day and now temp is in the 60's... While riding sometimes I find myself adjusting the mix on my carb a 1/4 turn or so. The mix screw does not need a screwdriver and is the big one right on top. Counter clock-wise lets in more fuel = richer and clock-wise less fuel and will make it leaner.

I have Big Radius pipes and and on de-accel get rumble (no popping) - if she starts popping, tweak the mixture screw slightly until the popping goes away. Usually this will get you dailed in about where you need to be.

Lambo - does adjusting the screw make any noticeable difference? - the screw is only for adjusting the mixture at idle

 

[RRRUFF]

Hey Sul, when you say go up on the int jet, do you mean the number size? Now that it is colder here it will studder when winding through the gears at about 3200 rpms and after the engine is hot it will cough back thru the carb when I roll the throttle kinda quick. It will pop when starting 90% of the time out the exhaust when hot. Had a guy at the oppsite gas pump almost leave this world once when I fire her up. LOL he didn't see the humor though.

 

[RRRUFF]

Thanks for the info Sul!

 

[LamboV12]

Lee - the name is a misnomer. It influences mixture outside of idle range...
Just try it and you'll feel and hear the difference. For example on down shift and de-accel, even though the engine is turning RPM, the carb is at "idle" becuase throttle is off... Ride and turn it about 1/8 of a turn and you'll get the drift. Set it back to where it was, then turn it the opposite direction and feel the bike. You can do it while riding at the same time.

If you end up going more rich than current set up, your idle speed may drop, then you'll need to use a screwdriver to reach the idle screw.

 

[lee]

thanks Lambo - I've never thought about it like that before

 

[Mickeetwo]

My Dog was popping on decel also. Tried your suggestions. Checked the exhaust bolts and the fronts were a little loose. Helped some on the popping but was still getting some. Turned the mix screw about 1/4 turn, no more popping, sounds much better just rumbling. Thanks again guys.

 

[acutigerfan]

Great thread with answers. I am in the same boat with the popping and some firing out of the carb. Actually, she has been running awesome here in Charleston, SC until the LAST two days or so. Never did (or would) I think about the cooler air temp. compared throughout the summer. On average, the days and nights have been ranging from 72-101 degrees F. On the otherhand, the last couple of days, we have experienced a cold front and Fall temps. They have been ranging from 57-70 degrees and all of a sudden..Pop..Pop...fire...pop...fire. Holy crap! What did I mess up this time??
Anyway, thank you all for your posts and info!! I am going back out to the garage with some determination and great advice!! Hopefully, the tuning and such should work. That has to be the problem...nothing has changed but the weather...

 

[woodbutcher]

acutigerfan, do and intro and pin yourself on the map in the tool bar. let us know something about you and where in charleston you are located