[Reaper1999]

I have a 1999 CBR 900 RR, It has 24,000 miles on it, engine rebuilt 10,000K ago, Stage 3 jet kit. I just started a new job which has me riding 42mi each way, in the past 2 days I've noticed it has been stuttering alittle on its own at a constant speed or when i let off and re-apply throttle, I'm hoping its a light blockage that could be solved with using seafoam, also (shame on me) I've been using Mid-Grade fuel, Hope someone out there has some good news so I don't get stuck on the side of the rode, Thanks

 

[cbr900racer77]

Is this something new that has started happening? My first thought would be you have needles too high but if it's something new, that wouldn't be it.

 

[Reaper1999]

Its something new, but it does have an erratic idle, but it does have stage 3 jets. I'm not sure if its vacuum synced correctly. I've been wondering if its due to me removing all the fairings (damaged at a drag strip by previous owners, started to crack even more). I tried to test my theory by drafting a large pickup truck, the bike smoothed out immediately. I think it might increased air flow throwing off the fuel/air ratio. Its most common in high wind, and speeds of 65mph and above, once I twist the throttle more smooths out till i come to a steady constant speed

 

[cbr900racer77]

Raise your needles another clip and see how it reacts. If it's the needle that's doing it, it'll either get better or ALOT worse. Then you'll know which direction to go.

 

[Reaper1999]

What would be alot worse?

 

[cbr900racer77]

I meant it would hicup alot worse. If it did, you know raising needle was wrong way and go back and drop them 1 notch below what you are at now.

 

[Reaper1999]

oh ok, not like if I left it un-changed it would fail. Do you think that with most of fairings off the bike that I'm leaving it with recieving too much air changing the fuel/air ratio

 

[cbr900racer77]

Too much air is a good thing. Every single performance upgrade out there is designed to do one single thing...get more air into/out of your engine. If you're getting more air than you were, just compensate with more fuel. Plug checks are your best friend here (unless you have a wideband with datalogging capability). Adjust needle til you get smooth acceleration during a roll-on then run it up to redline and shut off engine while pulling in clutch. Pull a plug after coming to a stop and check. If you're running pump gas, should be a very light brown/tan color to plugs. If you really are getting more air to intake, plugs will look almost like they did out of the box.

 

[Reaper1999]

Gotcha, I'll try that when I change the plugs this weekend, I'm gunna use NGK Iridium plugs

 

[cbr900racer77]

great plugs IMO.