Hello all,

I've noticed from owning the Big Single and visiting this forum that Backfiring seems to be a common thread among owners.

I just wanted to get a little clarification on what people are referring to as backfires.

When I first got my bike, an 03 LS650 hand-me-down from mom, it appeared completely stock except that the air/fuel mix plug had been removed. The bike would backfire when I turned it off. A clear, loud pop or crack. There did seem to be a connection to the idle setting and when I adjusted this I would get just a nice poof on shutdown, a backfire.

Since then, I've gone to a straight, unbaffled short pipe with K&N filter in the airbox. I wish I new my jet size but mechanic re-jetted the carb and I'm not cetain about the spacer mod. Maybe next time I'll have the courage to re-jet the carb. I also put in the Raptor petcock and plugged the vacuum port on the carb. My fuel/air screw is somewhere around 2 1/2 turns out. I ride daily to work which is a 52 mile round-trip. Lately I've been travelling the interstate at 70-75 mph because my two-lane back-road is under construction.

Here's how she runs now and where I'm wondering about backfiring... If I decelerate abruptly/rapidly without holding the clutch in I get the rumbling or stumbling from the engine consistently and sometimes when letting off the throttle to change gears I get the same rumbling/stumbling from deceleration.

Is this considered backfiring?

If it is, should I be concerned about it?

Even if it isn't backfiring should I be concerned about it?

As of today, I rarely get an actual pop or crack backfire and that is usually when down-shifting from third to second gear.

She seems to be really happy the more throttle I give her.

Any help and/or clarification is welcome.

D

To be perfectly clear,... a backfire goes through the carb...
Technically,.. these booms that we get, are afterfires... they go out the exhaust...
... but nobody knows what yer' talkin' about when you say "afterfires" so we say backfires...
...

Anyway,... pops, and blats, and wooble-wobble sounds on decel, are just a big thumper's way of announcing itself...
The gunshot "kerpow" sound is a problem, and should be dealt with...
It can come from being too lean, or too rich, or having too open a pipe...
... or a leaky or loose pipe or muffler...