Carb Jetting Advice

So now that I have the new to me '91, I am addressing the lean running issue. The bike runs very warm and cooks your ankles, starts and idles fine after taking a while to warm up. Lacks top end power and surges under acceleration from about 1/4 or 1/2 to full throttle, so I suspect it is running lean. I pulled the carbs and did a good cleaning and checking of the jets. All of the jets are the stock 40 pilot and 130 main. Found a little gunk in the pilots which was cleaned out, but not much. Reinstalled and tested the bike and it ran about the same, which I expected.

What pilot jet, main jet, needle shims (if necessary) has anyone tried that works well? Stock air filter and a Vance and Hines slip on is on the bike now. It would be nice to know so I don't have to pull the carbs as much.

Thanks.

 

How strange, I ran a wide open Delkevic can on my standard 93 and it was completely fine. Has it got the PAIR system installed? I'd be surprised if it needed jetting with no heavy mods. Is the fuel filter clean and the fuel pump fine?

 

PAIR system is intact. Does removing/blocking it off help? I thought it only injected fresh air into the exhaust to help with emissions?

Have not checked the fuel filter or fuel pump. Are they typically suspect on these bikes?

 

not usually but they would cause a weak mixture. As said in a prev. post, these bikes usually run rich if anything

 

Rich? Hmmm. Ok. Well, I will check on it and let you know.

 

I'd hazzard a guess at a dirty, clogged up fuel filter and/or a faulty fuel pump might cause hesitation and stuttering. The other thing to try is resetting the idle mixture screws. As standard they're meant to be 2.5 turns out from seated (lightly seated!) which seems to cure a few woes for people with running issues.

 

Gen 4 bikes run lean at medium-to-low rpms due to EPA-mandated emission limits, and they are naturally prone to surging at low throttle openings. I needed to instal a K&N/Dynojet kit to cure the surging and improve overall performance on my '97.



As a start, experiment with opening up idle mixture screws a bit as John above suggests. :livid: