This bike is driving me nuts

[Beer Runner]

I had a problem with the choke plungers, so I moved the choke cable around so the plungers can go all the way down. Now it runs better.
But the problem I have now, for some reason is that it backfires, but only when warm. So I adjust the idle a bit and it still dose it.
It never backfired bofore this so what should I look an this time?
1981 XJ650
Thanks again.

[BuzZz]

Idle air screws set too rich?

[Beer Runner]

It's just above stalling. The way it was before I had to keep my hand on the throttle to keep it from stalling, Oh what a pain that was.

[goodcruisin]

ive got a 80 650 special, i believe theye the same engine
the carbs on mine arenon adjustable so doubtful the air mixtures been altered. my bike also popped under acceleration, had one plug always foul,
replace your plugs if its been awhile. worked for me.

[mydlyfkryzis]

Idle mixture too lean often causes backfires. A lean mixture won't fire, letting unburnt fuel/air into the pipes. The next time the cyclinder does fire, the exhaust ignites the mixture and it and pops. Try richening the idle mixture a little.

[kar_the_terrible]

I had to deal with the same problem on my bike. Im assuming yours is a twin with CV carbs?
In my case, I had to work with the idle mixtures at least 3 times before getting it right. I dont know why, but it does not work on the first try. That was a month ago, Ive ridden it since then almost everyday to work, rain or shine and no issues (except immediately after rain).

check your air filters. they may be clogged making ut bike run too rich??

K

[twowheelindave]

Plugs worked for me. Could be a posssible intake leak too, air crews are a good guess too.

Good Luck! Dave

[dr_bar]

when my bike backfired, I took it in to get adjusted, (I had just bought it from Mapleridge Motorsports) They couldn't find anything wrong with it, a friend took a look at the bike, started it up, said I had an exhaust leak and it was the likely culprit. Apparently the exhaust will allow fresh cool air enter the pipes and it helps to ignite unburnt gases. I tightened all my exhaust fittings, no more backfires, (Except the odd one while under compression going down a hill, but that's got more to do with the after market exhaust system, V&H classics.)