06 xr650l backfire Heeelllpppp!!

Just bought a 2006 xr650l with 1500 miles. It has big gun (evoX) full exhuast, hotcam, K&n, and smog blocked off. I dont know if it has been jetted. It backfires really bad when decelorating or reving it up with no choke on even when warmed up. If I add just a tad of choke when riding there is no backfire and it is really responsive. Is there anything I can try before taking it to the shop? Any help would be great. Thanks :banghead:

Just bought a 2006 xr650l with 1500 miles. It has big gun (evoX) full exhuast, hotcam, K&n, and smog blocked off. I dont know if it has been jetted. It backfires really bad when decelorating or reving it up with no choke on even when warmed up. If I add just a tad of choke when riding there is no backfire and it is really responsive. Is there anything I can try before taking it to the shop? Any help would be great. Thanks :banghead:

First, check to see that the gas is fresh and clean.

Could be bad gas, contaminated with water too.

Pull the float bowl, check for junk in the bottom.

While there, remove the jets, and find out what size jets, and clean them out (with compressed air).

The main is probably to small, and the pilot jet is probably clogged.

+1 on clogged pilot circuit.

If all those mods are done already, the PO had to have enough knowledge to know that the carb should be rejetted. Check the numbers anyways while you clean the restricted pilot circuit.

Could be a plugged pilot or...

Since you live in California, you probably have the California carb version (which may be the same for all of them now). The smog pump itself caused a lot of popping. But even if you remove it, you will still have some popping on decel and after reving if you just capped off all the vacuum ports.

You want to make sure that the vacuum port on the right side of the carburetor (the one that's on top of a diaphragm looking thing near the throttle pivot) is connected to the port on the front right top of the carburetor - there should be 2 ports there and you want the one on the right hand side. For clarification, I'm saying right and left from sitting on the bike POV. I had the same problem until this was hooked up properly on my '07.

Also check your choke cable specs and adjust if needed.

Thanks for all the posts, will try this weekend.

I would check and see if they Bumped up the pilot jet to a 55.

I betcha it is still the stock pilot jet. A little fatter pilot jet will cure it.

If you end up where you think the jetting is good, check the valve clearance to make sure one isn't on the tight side and also the cam timing. If the cam is off a tooth it'll run, but will backfire all over the place. You might also make sure there isn't a leak someplace between the carb and the cylinder head causing a lean condition.

evomx971

Chances are the Big Gun is breathing a lot more - i.e. a lot less restricted than your previous pipe. If you left that carb the same , that means your bike is now running lean (more air, less fuel). A lean condition will cause popping when you decelerate.

You need to re-jet the carb to run richer as suggested earlier.

When you put the choke on, you are adding more fuel (less air) to the mixture, which temporarily stops the popping / backfiring.

Also as suggested by evomx971, you might have a leak which is letting even more air into the mixture.

But I'd guess it's just a case of "new pipe, therefore new jetting".

I've learned the hard way that you almost always need to re-jet the carb when changing exhaust systems, especially when changing to a more free-flowing exhaust.

Chck this thread, same problem....

http://www.thumpertalk.com/forum/showthread.php?t=594585

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