View Full Version : Carb Adustment

10-11-2010, 4:43 PM
OK, so I did a rejet to the slow speed jet, moved up to a #48. I adjusted the idle to about 1200rpm. I tightened the idle mixture screw all the way in and turned it out 2.5 turns. Now if backfires rolling to a stop just like before the rejet? And when I start it cold after a long ride it backfires like a canon? All these adj. were given to me by my local mechanic that wont do rejetting because its in california and not allowed. All this started because I swapped my stock racetrack air cleaner with a Ness big sucker cleaner system. Any advise? I dont want to use another mechanic thats going to charge 150 bones to adjust it!! Thnx. Its a 98 1200 sporty.

10-11-2010, 5:31 PM
Otherwise stock cv carb? I would try 3 to 3.5 turns on the idle, and take it back down to a #45. The way I understand it is...idle mixture is for idle (after choke,) slow jet is just off idle, part throttle, and the main takes over around 50-60% throttle.

Did you make the adjustments with a warm or cold engine?

10-11-2010, 5:37 PM

10-11-2010, 9:33 PM
Redryan, ya Ill take it out a couple of more turns, and its a stock carb. I have been making the adj with a cold engine. Each time I go out I took a half turn to see if it changed anything? Ill mess with it some more, its a no brainer im sure! Runs fine, just dont like the crackling.

10-11-2010, 10:07 PM
are you running baffles?

10-12-2010, 3:55 AM
Now if backfires rolling to a stop just like before the rejet?.

If I read this right, that sounds like cold air mixing with hot exhaust gas. Exhaust leak.

10-12-2010, 10:13 AM
do your idle adj hot running at idle speed, adj the idle a little lower then normal so you are well into the idle circut then slowly turn the idle mix screw in (clockwise) and listen for the idle speed to start dropping then slowly turn the screw out in small increments until you reach the fastest idle speed and then reset your idle screw to the proper idle speed.

10-12-2010, 10:20 AM
no more than 4 turns out. if you gotta go more than 4 your slow jet is too lean.

10-12-2010, 12:22 PM
try replacing your intake seals

10-13-2010, 10:32 PM
Got It! 3 1/4 turns out and adjusted idle up slightly! Runs like a top! Knew it had to be simple, thanks for all the help!