Carb Tuning Help

[Ainon]

Hey guys,

I am currently riding a 99 Buell cyclone with a freshly rebuilt engine. Anyways, I just got the engine in place. I set the timing, and set the carb up with a 200 main jet.

Right now the bike has a Vance Hines exhaust and aftermarket airbox.

My problem is that the bike seems to go flat at about 60 mph in fourth gear. Fifth gear seems to be flat also. I assumed that I am running lean. But if I move the needle up half of a notch with a washer it seems like im bogging down and losing low end power, and my top end doesnt improve much.

Any ideas? Should I move down a jet size?

 

[knwyman]

FWIW, I had a 99M2. I ran a 185 main & I was pretty close to sea level.

 

[Ainon]

Hmm I'm a little bit stumped as of now.

From what I understand,

Slow jet effects idle to 1/4 throttle
Needle / Needle jet effects ~1/4-3/4 throttle
Main jet effects 1/2-full throttle

So being flat with WOT, I assumed my main jet was too large. I tried the 185 main, and for some reason the bike idles horrible. It has pre-ignition problems, and backfires through the carb and pops. I tried 190 and had similar results. With a 195 main, I was close, but still had some lean popping. I advanced the timing 3 degrees past its stock position (to make it run better lean) and it runs without popping, but the top end is still flat.

I'm stumped. Why is my main jet effecting my idle conditions?

 

[Ainon]

Could my idle screw be in too far, essentially cutting off my idle circuit?

 

[Ainon]

Hmm that would not make sense either. In idle, the fuel flows through the slow jet and then through the idle mixture screw correct?

Seems like there is no way the main jet should effect idle... Can't figure out why moving down a jet size creates backfiring through the carb at idle.

 

[bigblaze]

What pilot jet are you running? problems on idle=pilot circuit. Pilot jet and mixture screw. 200 main is too big also.

 

[ReconLdr]

What do the plugs look like???

 

[89rs1200]

I live at 5,000 feet ASL. K&N air filter and race exhaust, So the 185 main jet works best for my S3's and RS1200. At sea level the 185 or 190 main would be best.

All buell's were lean from the factory to meet CARB regulations. Up one size on the secondary/idle jet should fix your problems.