Hello I just purchased a 1993 CBR 1000F its got Yoshimura slipons, K&N filter, and i just rejetted my carbs ...and on deceleration it sounds like a gun going off on 4th of July....the first time was funny as hell when it scared scared the crap out of some teenagers walking down the street, but now its going off everytime I down shift.. any feedback would b much appreciated.....

 

I'd say over rich mixture and/or stuck, burnt exhaust valve

 

If you upped the mains on the carbs - consider it pretty normal two of my
bikes with bigger jets pop quite a bit more on downshift. Myself I'm thinking
some upgraded diaphragm springs might be in order to close down the needles
a bit quicker to lessen the amount of fuel getting dumped in on decel

 

Aftermarket slipons will cause some popping on decel, also a richer mixture and leaking exhaust gaskets will cause this as well.

 

I've seen this more on cars. Popping is usually a lean mixture caused by a vacuum leak or extreme jet leanness. Or can just be caused by the throttle being closed quickly.

Backfire is completely different. An explosion in the exhaust or intake caused by ignition at the wrong time, with an exhaust or intake valve open. Usually the ignition goes off at the wrong time. Can be caused by ignition problem, or hot carbon or the hot edge of a spark plug sticking in the combustion chamber.

 

all good points - but as you did what I did - bigger jets - it's unburned fuel in the
exhaust manifold popping when you let off the throttle quickly in conjunction with
downshifting further decelerating rpms

I'm not that worried about mine it I kinda like the burbling popping it makes

 

Yep I agree with Sprock. Unburnt fuel causing the issue. I've had a few bike's that I've fitted after market pipes all with similar outcomes. My 1200 Suzie has the choice of standard slip on and one I call 'noisey boy' The standard has no popping, how ever noisey boy pops and cackles away under deacceleration. Primary cause is a lack of back pressure allowing unburnt fuel into the pipes/muffler causing the popping.

On a previous bike I had years ago, this popping was excessive and LOUD, no amount of carb fiddling solved it. Our local custome bike muffler manufacturer solved the issue. They fitted a pair of custom made plugs to the inards the mufflers that increased the back pressure but still allowed the bike to have that nice growl and no real noticable drop in performance. This took a bit of fiddling getting the match right right, but once done, there was only an ever so slight occasional muffled pop if really pushed things.

Cheers

 

Right on Andy now that I think of it - anytime I fit the DB killers - guess what

It kills the popping and burbling too - back pressure forsure - downside to DB Killers
is they kill the growl so yeah internal chambering would do the job like you mentioned
I reckon