Occasional 'backfire' on a closing throttle...any ideas?

[mhsilverw]

My Rockster is std - pipes/exhaust. If I stay in 3rd or 4th gear and ride on 'revs' I am getting an occasional backfire on a closing throttle...has happened once or twice now.

Is this normal? As the bike is std / fuel and pipe-wise this surprised me - has anyone else experiened this and cause or symptoms?

Mark

[Moore4u]

Maybe need a valve adj. ?

[Unklian]

Maybe need a valve adj. ?

I bought my Rockster 2 years ago.

the same day, I fitted a "Y" piece instead of the cat.

My bike had an occasional bang on the overrun usually after a long decelleration
from high rpm then at about 2000 - 2500 there is a bang. Sometimes, a loud crack,
sometimes a muffled thud.

After new plugs, setting the valve clearences accurately and a TB balance, it is
not EXACTLY the same. Less of one big bang but the occasional two or three muffled ones.

It has managed for two years and a lot of miles with no ill effects.

My next thought was exhaust air leaks or ignition timing but.......

It'll probably go on for ever so I'll probably just leave it.

Ian.

[boxermania]

mhsilverw

First a backfire here and there is nothing to worry about. Most of the time they are caused by a slight leak in the exhaust system, usually around the clamps from the exhaust pipes to the cat converter. Another posibility is if your TB's are slightly out of sync. One of the most important things for the proper operation of the boxer engine, everything else being equal, is the TB sync.

You might think about it if it hasn't been done in a while, the idle sync would be helpful too.

Good luck.......