hey everybody...noob here...got a 99 cbr 600f4 last year....27000 miles but really clean and well maintained....ride every weekend...not far...maybe 25 miles or so at a time...never had a problem until saturday...was down-shifting coming to a light and all of the sudden I get this backfire and now the bike misses BAD and has aVERY LOUD popping noise coming from front of engine !! like a super loud pop-corn maker!! WTF !!! [:@]...seems like its right under the front of the gas tank...lost all power...feels like compression's gone...backfires when i pull the clutch...thankfully I was close to home so I babied it home at about 5 mph and shut it down...called a dealer and the service guy says it might be the exhaust header separating from the head ??!! but of course "I need to bring it in so they can look at it"...not convienient right now...so i took the lower and upper fairings off last night and the headers are fine...so i started it up and shut it down real quick and the loud POP is coming from under the front of the tank ?? there's a small diamiter rubber hose that jumps big time everytime it pops...but i cant see what's it's connected to...runs parallel front to back and has "TA" on it with 2 small up-arrows ?? I've got a pic but i cant attach it here...i can send to regular e-mail if anyone can help...anyone have any idea ??so far I've heard it probably ISNT the CCT....signed cbr-less-and-bummed-out in michigan

 

It sounds like you may have dropped an intakevalve. With valve stuck open, it will let all of the compression of that cylinder back through the carbs and when it fires, it will backfire through the carbs. Your air intake is right there and the noise will pop there. I would pull your tank, pull your airbox cover off and start it again. Stand back and see if your getting backfire through the carbs. this may suggest that you have a stuck or brokenvalve. It may also suggest bad ignition system (sparkplugs, coils. ect).

Another thing, a little less likely is a change in timing. I doubt the timing would have changed, but you never know.

first things that are simple. check plugs. check wires, check coil for cracks.

Unless your mechanically inclined, I wouldn't reccomend tearing into the engine to far. You may end up bringing the bike to a dealership to figure it out. I would start by asking them to diagnosis it. Then decided if its something you tackle on your own to try and save some money.