backfiring through carb

[PA Jim]

I recently scooterized my 800 classic (sort of) I made my own backplate, I did not modify existing one. I used a .165 main jet, .050 pilot jet with the misture screw out 2 1/2 turns. I am getting a backfire through the carb when giving it just a little gas. It runs fine during harder acceleration. Any help would be appreciated.

Thanks,
Jim

[1400pilot]

maybe caused by an exhaust leak at the header gasket

[PA Jim]

The exhaust was not altered it is the same exhaust that was on the bike from before. Hard Krome slash cuts

[1400pilot]

a backfire can be caused by a lean condition, have you checked for small vacuum leaks, if not try and richen the mixture up a bit...............I see our resident 800 expert is looking at this thread now, so your troubles will soon be over.................Hi ya woody!!!!!!!

[woodchucks800]

Originally Posted by PA Jim

I recently scooterized my 800 classic (sort of) I made my own backplate, I did not modify existing one. I used a .165 main jet, .050 pilot jet with the misture screw out 2 1/2 turns. I am getting a backfire through the carb when giving it just a little gas. It runs fine during harder acceleration. Any help would be appreciated.

Thanks,
Jim

I'm betting it's an air leak either between the carb and air filter or between the carb and the intake boot. the rubber boot is known for causing problems just like this. Have you already removed the epa crap( i'm assuming you have)I'd probably turn the mixture screw in a half a turn also.Set your idle up a bit as well.

[mumbles]

Like mentioned before, make sure the rubber boot from the carb to the intake is well seated.

This question is for everyone: Can the rubber boot be damaged easy?


Woody, if this is caused by a lean condition wouldn't turning in the mixture screw make it more lean?

[woodchucks800]

Originally Posted by mumbles

This question is for everyone: Can the rubber boot be damaged easy?

I don't think it can be damamged to easy buy anythings possible making sure the carb is seated in the boot properly and the clamps are tighten just right(not to tight or too loose) .

[2WheelFun]

What setting is the carb needle set at now?

[woodchucks800]

Originally Posted by mumbles

Woody, if this is caused by a lean condition wouldn't turning in the mixture screw make it more lean?

I don't think the jetting is causing his problem. He's more than likley got an air leak between the carb and the modded stock air filter case or from the manifold boot. The only reason I suggested turning the A/F screw in is because he's still using the stock needle which won't seat into the new 50 pilot as far as the aftermarket needles do. For the most part after changing the jets and needle everyone tends to turn the A?F screw ina 1/4 to 1/2 a turn before there playing with the set up . I know I'm running at 2 turns out and not running lean, but his could be different( they all are) and without an adjustable needle there isn't much he can adjust other than the A?F screw ( He might be able to add a shim under the needle but I don't think this is where the problem lies)

[PA Jim]

Thanks for all the input guys I appreciate it. I am running a dynojet needle out of a 1500 on the 3rd notch from top as is stated on Russian Wolf website. Anyway, I took the tank back off and checked the seal between the manifold and the carb, seemed ok. Turned the mixture screw all the way back in then out 2 1/2 turn, reinstalled filter backing plate and filter. Started up went for a ride, lo and behold no more problem. Thanks again, you guys are a wealth of knowledge.

[bluestringer]

Like Woody said, it was an air leak. I'm still getting a pop through the carb when cold. I think I'm running a little lean, because I still need the enricher quite a bit. Running the air mixture at 2 and a half. Just installed a 40t rear sprocket, now running 18/40, and I really like the long legs.

[PA Jim]

Hello Again, thought I had this taken care of, but I still get the sneezing through the carb when I ride in cold weather, does not do it when it is warm. Any suggestions?? Thanks in advance for the help