78 kz750 backfire

I bought a 78 kz750 last year. I rebuilt the carburetors and fixed the timing but my bike pops and backfires when I get off the throttle. I'm not really mechanically inclined, any advice on what I could try to fix this?

Do you have the stock air box and air filter on the bike? Ed

Forgette36 wrote: I bought a 78 kz750 last year. I rebuilt the carburetors and fixed the timing but my bike pops and backfires when I get off the throttle. I'm not really mechanically inclined, any advice on what I could try to fix this?

Popping through the exhaust on deceleration may often be reduced or eliminated by slightly enriching the carb pilot circuits.

Could try turning each pilot mixture screw out counter-clockwise 1/8 turn.
If that doesn't help enough, go another 1/8 for a total 1/4 turn.

If the pilots circuits are not "as-new" clean, they may provide less fuel mixture at the same setting compared with "as new" clean pilot circuits.

Good Fortune!

Patton wrote:

Forgette36 wrote: I bought a 78 kz750 last year. I rebuilt the carburetors and fixed the timing but my bike pops and backfires when I get off the throttle. I'm not really mechanically inclined, any advice on what I could try to fix this?

Popping through the exhaust on deceleration may often be reduced or eliminated by slightly enriching the carb pilot circuits.

If it's a 750 twin with Mikuni BS-38 carbs, up the pilot jets to #50 and it will help. You may also have exhaust leaks at the pipe. Popping can also be caused by an intake leak. Make sure the fuel levels are set at 5 mm.

If your coil is original, it needs to be replaced.

If the timing advancer is stuck it will cause popping and other problems.