Exhaust Backfire Problem

[Gearheadtom]

I've got at '85 200m, with a 200e motor in it. The problem is that it backfires sometimes when I downshift. It used to only do it if I downshifted very quickly, but today it would do it just from first to second, even with the motor at a lower RPM.
I adjusted the exhaust valve before to try to fix it, but that didn't help. Any help would be nice.

[Dirtcrasher]

Good size backfires are from unburnt fuel and either something is not stock, or something is plugged up etc etc.

A little pop pop pop (ESP. deceleration issues) is usually fixed with a 1/2 turn of the airscrew under the front portion of the carb........

[Gearheadtom]

I believe my exhaust is all stock. I think the problem is unburnt fuel getting into the exhaust, and igniting, from to rich a fuel mixture. I know my engine is running rich due to a worn needle jet, and I have not gotton around to getting a new carb kit. Is that what my problem is?

[Erics350x]

Could be, i'd start by setting the carb and vales to stock specs. Does it idle ok?

[Daddio]

Leaks in the exhaust can allow fresh air into system during deceleration helping the unburnt fuel to ignite and causing a "backfire".

[harryredtrike]

i agree with daddio exhaust leak has done this to me

[Gearheadtom]

I have one small exhaust leak where the head pipe connects to the exhaust. I would put the carb to the stock setting, but its running so rich on the leanest setting, I think it would barely run.

[Russell 350X]

Get a carb kit, fresh plug and adjust the valves to factory specs. Try the clip in the middle position after you put a kit in it, and go from there.

[Gearheadtom]

I just adjusted the exhaust valve, and it is still doing the same thing. The next thing I do will be get a carb kit.

[Hair Bear Bunch]

My 250es started backfiring a while ago, wasn't until i rolled it and had to do some major stripping down for cleaning I took the heat shield off, and suprise, the exhaust was leaking at the joint. A liberal application of 'GunGum' later and no problems since.
I'd get some exhaust paste into the leak before you go much further. It's cheap and might solve the problem straight off. Either way, you're going to have to fill the leak at some point!
Good luck.

[factoryX]

lol, my old 200x with a cobra would shoot flame 1 foot out the silencer when it back fired.

[Vealmonkey]

If you have an exhaust leak at the head, I would also advise you to get a new exhaust gasket, that may help to either lessen or solve your backfiring, but a carb rebuild kit will help with your carb issues. They might be 2 unrelated problems.

[Gearheadtom]

I fixed the exhaust leak, and I took it out for a small ride, and it seems not to be backfiring anymore, but I'm not completely convinced yet.