Why is my Suzuki S40 backfiring?

Question

I have an 07 S40 with only 2000 miles and it backfires everytime I slow down without pulling the clutch in (so when I let off the gas without shifting). The salesperson said it is due to the single cylinder, is this correct or is there something bigger going on?

Answer 1

I don't know the cause of the backfire, but I do know that the S40's are notorious for doing that. So it's not just your particular bike.

Answer 2

Backfiring on deceleration is due to a lean idle mixture.
Check the intake manifolds and make sure the clamps are tight.
Richen up the carburetor mixture screws 1/2 turn at a time (clockwise) and check for a difference.
Count how many turns you make, in case you want to turn them back to where you started.

Answer 3

Oh who knows.

Um, you're not running with the choke on, are you?

Anyway, pull the spark plug, clean it, check its gap.
Check the oil level in your engine and make sure it's just right -- if there's too much, let some out.

Try running a tank of premium gas. Or, buy some carb cleaner gas additive and add a quarter bottle to your full tank of gas. (Seal the bottle up really tight, for future use; I use glad wrap).

Inspect your air filter element (if you have one). Clean it (if it can be cleaned), or replace it, if it's too dirty. Don't ask me to define "too dirty." I don't know.

Anyway, motorcycles aren't supposed to backfire when running properly.

Answer 4

Yeah, it's normal for that bike, I have one also. It doesn't happen as much as it used to, as I got smoother with the controls...but still when I let off the throttle quickly it will do it. Just the nature of the beast. It depends on where in the cycle the piston happens to be sitting when the throttle closes.

Answer 5

Thats normal u may want to have it dyno,you could put a better air filter on it but its ok.