when i gear the bike down (2000 vfr 800 2300kms) im noticing some backfiring almost sounds like popcorn popping. Just wondering if this noise is a result of my pipe wearing out or some tune up issues. Any advice would be appreacited.
Backfiring Is this on deceleration, or during normal riding. Also are you fuel injected or carburetor?
A little popping is normal, at least in my experience. I know my 98 i just purchased has a lil snap crackle and pop when engine braking.
On engine compression you cause a Vacuum in the header this in turn sucks in fresh O2 from a very small leak in the header changing the mixture so it will ignite giving it pop, won't take much but that is what it is IMO.
I've got an '04 and mine does the same.Have just recently removed the little air snorkel on the top of the airbox ,and popping very noticeable now, sounds great to tell the truth because it does it on soft deceleration as well.
Yeah, i love a little grumbly popping on decel, sounds mean haha. Im sure it's just normal in the OP's case.
Decel popping Now for the 64 cent question... is it a constant popping IE: if you go down hill engine braking does it contiguously pop, or is it only the occasional pop-pop that eventually subsides. If it is only occasional when you immediately roll off the throttle this is normal if it is continuous then this may be one of several things. 1. Too lean of an engine condition. 2. intake manifold air leak. 3. Exhaust manifold air leak. Have you changed the air box, and filter to get higher flow? and have you changed the exhaust for higher flow? if this is the case you may be just out of spec that the FI computer cannot compensate for it. If no, check the boots at the intake manifold for signs of cracking around the rubber, if you see any replace them. If this all looks good then check for exhaust leaks, Good way for this is light a cigarette and while the bike is running let the smoke drift over the manifold attachment points if you see it puff away you know you have a leak. If you've done no modifications, and are experiencing constant popping check your injectors to see if they are clogged (or run some tanks with injector cleaner) this can also cause a lean condition. With the new fuel containing alcohol this runs somewhat hotter and leaner than gas with MTBE this can also fool your FI computer into thinking it is delivering the correct mixture when it is running too lean. VFR's unfortunatel have little wiggle room on the lean mixture as the engine was designed and configured to run as lean as possible to meet emissions standards. so it does not take much to put them into a too-lean state.
I have an '07 and after I put in the K&N and the two brothers stash exhaust mine will pop it I give it a little gas at idle or a little when I am down shifting. I didn't get a programmer for it but everything seems to work fine.
Mine only gives a little pop here and there, it's not constant, but consistent, nothing out of normal I feel, Everything seems to be in order and she runs smooth as silk. As for the mods all I have is Staitunes. Not even worth a mention but thought I would jump on thread with DAN DOG and let him no he's not alone.
All in a dyas work. Its normal, My lazes with the full on race spud, only pop occasionally. Generally on Deceleration and usually on a hill. Otherwise pure rumble. Its usually Roll off Pop-Pop-Pop-Pop done, If it was carbureted I would open up the idle Jet just a bit. and this would solve the issue. But its not severe enough to warrant addressing as it is so minimal that it really doesnt warrant attention. Now if we were talking about my Harley, Oy-vey. Roll off and it poppppppppppppppopppppppp. Needed to Shim my main Jet, and open up the Slow Jet to handle the K&N and the 2-1 4" exhaust. Also had to replace the carb seal gasket as my was cracked and leaking a bit of air. Unfortunately this meant, replace gasket, test, Shim main Jet Test, replace slow Jet re-test. Of course being very old school mechanic, I got it very close Just on sight inspection of the plugs. Then took it to the shop and hand them run a exhaust Gas analysis to determine how close I was. Long story short the main jet shim needs to be .001 thinner. I can live with it being a bit rich. http://vfrworld.com/forums/images/smilies/smile.gif -Cheers!
