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Backfire????/Carb settings

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My Lifan backfires pretty bad,it only has maybe 10hrs on it.Runs great,idles great,good throttle response,it just backfires all the way down deceleration from full throttle.

Any ideas?

Would a real exhuast help,the header on mine was cut an inch(dont ask!lol) and it has a really crappy can on it.

Also my neighbor said its probably the mixture(but he runs full-mod crf50,mechanic maintained),but I've never got it just right w/o backfire.Its a mikuni clone,idle screw,mixture and the bottom one for the overflow.Whats a good starting point(turns from seated) for the mixture screw?

Or is backfire just something china/cheap pits do?

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try checking the exhaust gasket ring, make sure it not smashed/destroyed. My bike was back firing due to that problem

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+1 on changing the exhaust gasket, for a better seal of the pipe at the head. In order to run properly, a 4-stroke engine needs the back pressure from the exhaust, having loose pipes and leaks will contribute to backfiring on decel, creating a lean condition.

The Mikuni-clone carb uses a fuel screw, turning it IN leans the mixture, and turning it OUT richens it. A baseline setting to work from would be 1-1/2 to 1-3/4 turns out from seated, and make your adjustments in 1/4-turn increments to see how the bike runs. Any more than 3 full turns out, you should go up a size on the pilot jet. If you get to within a 1/2-turn from fully seated in, go down one size on the pilot jet.

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Cool,thanks alot for the carb tips.

My exhaust has no gasket(bought bike new),do I need one of those crush gaskets?

Like I said its a Lifan,so it takes a crf50/china clone type exhaust.It has the flange w/ holes for the acorn nuts about 2in from the end,and the end slides into the engine.(I know this is obvious,just trying to be thorogh).Then the acorn nuts attatch the pipe to the engine,is that where I need the gasket?

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Also how do I tell if my mixture is right?

I burnt up alot of RC(T-Maxx) engines running them lean.

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The exhaust gasket goes up into the exhaust port on the engine, just make sure there isn't an old one crushed flat in there before you install a new one. Sometimes, due to the carbon buildup, it's hard to see the old one crushed up in there. You HAVE to remove an old one before installing a new one.

With the bike shut off, turn the fuel screw IN until you feel it lightly seated, counting the number of turns as you go. Once you determine that, back it back out to where it was, counting the turns to reset it, or, setting it at the baseline setting, to adjust from there.

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