87 XR600R Still Backfiring?????????

can anyone help me, I can't seem to figure out why my XR keeps backfiring, it does it on acceleration and on deceleration, basically all the time. I tried adjusting the valves and that didn't help, then I cleaned and adjusted the twin carbs, I also went back to a stock muffler. No such luck. Has anyone else ever had this problem, or does anyone have a miracle cure. I'm about to start looking into the ignition, but the bike starts fairly easily and has good spark when I check it, so I'm totally confused...HELP PLEASE :devil:

have you checked the jetting? (main) looked at the plug? is it white? then go up a size or two. i think stock is 128? i've got 135's in mine, but it is all opened up.

check you air or fuel screw on the carbs. It should be somewhere around 1 1/2 to 2 1/2 turns out. Check you air filter too.

It could be a number of things. First Id look at the exhaust system, if you have any air getting in between the exhaust flanges, or the joint between the pipe and header thats part of it. If you have any air getting in between the intake manifold and the head, thats part of it. It could be both. Id run down the possibilities, new exhaust gaskets, and some high temp silicone at the pipe/header joint, then new gasket stuff on the intake manifold. Do not do a half ass job and just tighten these areas go buy new haskets, tightening them doesn't do anything. May even make your problem worse.

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