D & D causing backfire 98VFR

Does not happen often but it does at least 2-3 times on 20 mile ride mainly on deceleration.
I suspect its running lean and wondering if anything I can do to minimize short of buying another exhaust or worse putting that heavy stock boring muffler back.
I am concern that this pop up may cause damage to engine.Should I worry or this is nothing to be concern about.
Thank you

 

More than likely it's the 'popping on decel' that happens with most all bikes when you change the exhaust system without tailoring the jetting. It probably won't hurt anything (IF that's what it is). My '86 with a Yosh exhaust pops on decel, and it's been doing it for at least 10k miles now. I have a jet kit; but the bike runs so well I'm not inclined to mess with it.

You should try and lock down that this is - in fact - popping on decel, and NOT 'backfiring 2-3 times in 20 miles...'.

 

Thanks for reply.It is popping on decel and it is FI. I am just concern that this condition does not damage the engine.Like exhaust valves....etc.
I am not clear "You should try and lock down" What did you mean?

 

Sounds like you have 'locked it down'. You might be able to re-map the FI to eliminate the popping. Somebody with more specific experience should be along shortly...

 

It is nothing to be concerned aboot. Power Commander will help but nothing to worry aboot.

 

BTW, I wouldn't classify the popping as a 'backfire' (even though the physics are pretty much the same). Hitting the kill switch on a big twin in a tunnel - now that's a backfire.

 

Changing the pipes improved the exhaust flow, which increases engine vacuum, which increases the amount of air in the cylinder. Since the computer is still telling the fuel injectors to insert the same amount of fuel, this causes a lean condition. This is most exaggerated when you are decelerating with the clutch engaged (engine braking) because the engine is getting very nearly idle fuel, but you are forcing the engine to pull more air by turning it with the wheels.

The "popping" or backfiring occurs because the lean condition becomes such that one or more cylinders does not fire every crankshaft revolution because there is too much air in the cylinder for combustion. The fuel then gets pushed into the extremely hot headers on the exhaust stroke and detonates, make a "pop" noise. This is not ideal, but mostly harmless. Just be aware that running lean will generate a bit more heat than your factory stock bike would have.

I suspect this is part of the reason 7th gen vfrs run so damn hot and have all those flat spots in the throttle curve; the stock fuel mapping is too lean in places to satisfy emissions.