Backfire when you downshift, why?

Pater · 02-22-2004, 4:51 PM

What would make the engine/exhaust backfire or "pop" when you downshift coming into a turn. Is it something that can be helped by adjusting the fuel/air mixture screws? A little too rich maybe? The bikes a 94 f2 that has been jetted and has a two brothers full system. Not real happy with the exhaust. It's just too damn loud. Would a different exhaust help?

CBRBob · 02-22-2004, 5:09 PM

too rich or too lean will do it, lean backfires or overly rich filling up the canister and then firing. Keep the pipe, change the can if you want.

abtech · 02-22-2004, 5:29 PM

Remove the PAIR system while you're at it. They are famous for causing backfires on decel. Normally (if the PAIR isn't the problem) backfiring means you are a bit lean (although it can happen if you are WAY too rich as well). When you jetted the bike, did you change the needles as well as the mains?

ConqSoft · 02-22-2004, 6:09 PM

CBR 600's have PAIR valves too?

showmethebombs · 02-22-2004, 6:43 PM

quick way to tell...as your riding the motor braking compression...and you hear the backfire...move the choke on a little bit at a time...that will be a quick way to tell you if its too lean. I had that issue on my 97 F3 after it was piped and jetted. I then knew to richen it up after I did the "choke test"

so then just take the jets and richen them...do not ride around with the choke on.

Pater · 02-22-2004, 8:13 PM

The needles were changed and the clips were set per the directions that were with it. If the choke test doesn't work and I still get the backfire, am I just way too rich and need to tighten the screw up a bit?

thx for the info...

abtech · 02-23-2004, 8:54 AM

Quote:

Originally Posted by ConqSoft

CBR 600's have PAIR valves too?

Depends on the year. Not certain if the F2 has one, but my 89 Hurricane (F1) did.

The Sook · 03-05-2004, 11:04 PM

Pater, when you say Jetted, you mean a Dynojet Kit? If so, those directions are the problem. What's your bike got on it, besides the system? If the air filter is stock, then you'd really only need to adjust the standard needles and maybe up the main jet size. Nearly every bike we do down here, runs so rich if you put in the bike what the box says, it ain't funny. I'd put back the original needles, set them slightly richer, leave the main jets you've got in it now, or even bring them back a size, and if you've changed the pilots, put them back to stock. Then see how you go.