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1999 CBR900RR Fuel / Spark problem?

5010 Views 24 Replies 6 Participants Last post by  bangerz731
I had let my bike sit for 3 months and forgot to run the gas out the carbs before my vacation.

Now it runs rough, need to use more choke to start it. And I feel a surging / misfire at all rpms... It feels completely under powered at higher rpms and really feel the surging above 6k.

Clogged carbs? Spark problem? Thanks for any input.

Also it has 41k miles.
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Remove and disassemble the carbs => spray carb cleaner into everything hole and cranny there is, pull plugs, ground to frame and check for healthy, blue spark.
Drain tank and get fresh gas.
Check fuel filter and lines for flow.
Yea that's to much work, I called my local shop he will clean and tune for $140 that sounds worth it to me.
Really? To each their own, but it would only take about 1.5 hours and 3 beers...:D
Buy yourself a Haynes Manual.

Sit on the bog in the morning and have a good read - anything they can do you can do too... Might take you longer but at least your not having to rely on stealerships etc.

I'd rather put the $140 to a small parts washer and a few cans of carb spray.. then using a camera (if you need to remember where all the bits go) or make diagrams and count the turns (on the screws etc) I'd just go for it.
Hey twin, i was wondering how this forum comes about its little smiley face icons and who makes them?

I have a suggestion ;) ; rating jobs by beer.

ex. "this is a 4 beer job" => four little beer icons
Hey twin, i was wondering how this forum comes about its little smiley face icons and who makes them?

I have a suggestion ;) ; rating jobs by beer.

ex. "this is a 4 beer job" => four little beer icons
It would be quite a good gadget to have for the people who like a drink like myself, but what happens about the T-Total ones? :rotfl:

I'd like to think of it being a "Four Crate Job" :thumb:
:rotfl::rotfl:After four crates my bike would be missing its tank and front wheel
It would be quite a good gadget to have for the people who like a drink like myself, but what happens about the T-Total ones? :rotfl:
I don't drink and I don't use those stupid smiley things :)
But youre always so close with the :) bit!
I'm old school :)
Well I do have the honda shop manual and got all the carbs separated and started to break one down.

Do I have to take out the Main and slow jets out?
Well I do have the honda shop manual and got all the carbs separated and started to break one down.

Do I have to take out the Main and slow jets out?
If you want them clean then yes, you would need to remove everything.
But you don't seperate them from the rack unless the connecting pipes are leaking - the manual should have mentioned this.
This breaks it down for you, wrote it myself. And Bladeracer is very much correct, seperating them is not a good idea unless absolutely neccessary. After you assemble them you may have to sync them. I would've first ran some Seafoam through it, that stuff does wonders.
Carb cleaning 101 - RRZone Forums
Well I did find a nice size piece of that foam from the little box attached to the air box in one of the carbs. Got it all back on the bike started right up took it for a 10 mile test run on the country roads. I feels like is has more power but I still get some of that misfire feeling. could that be a sync problem?

Also if I try to slip the clutch in 2nd at 9k does not even come close to coming up maybe 3 inches.

I'm going to check the spark right now.
When its in neutral, rev it slightly. If the carbs are out of sync, the engine will take a bit longer to get back to idle than normal.
So I finished my full cleaning of the carbs twice now, also check my spark nice and blue... but shes still completely under powered when accelerating. Could it be my after market rectifier... or any other suggestions? Thanks
So I finished my full cleaning of the carbs twice now, also check my spark nice and blue... but shes still completely under powered when accelerating. Could it be my after market rectifier... or any other suggestions? Thanks
You said it sat for three months but you didn't mention you'd changed anything or done any work to it.
How long ago did you change the regulator?
Is the system charging?
How low does the voltage drop when cranking the engine?
Does it behave the same when it's fully charged?
I changed the regulator abt a year ago... the problem started after sitting this year june 1st to september 2nd. It still charges fine when running. Didn't need to be charged when I got back cranked over fine and started just needed more choke.
I changed the regulator abt a year ago... the problem started after sitting this year june 1st to september 2nd. It still charges fine when running. Didn't need to be charged when I got back cranked over fine and started just needed more choke.
Then if was fine for nine months with the aftermarket regulator I would suggest you can rule it out as the problem.
Carb synch is usually only a problem at idle.
Have you cleaned the fuel filter?
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