I have a 96 CBR900RR, heres my problem. Bike starts right up, but once it warms up usually after a few miles and the temp guage is mid point my idle goes from 1200rpms to 2000rpms then fluctuates from 1500 to 2000 rpms.
Any suggestions would be appreciated.

 

Did it just start doing that all of a sudden ?

What does it do if you 'blip' the throttle ?

You could start with the idle circuit adjustment screws but they normally don't need adjustment all of a sudden for no reason.

Need more info.

 

I don't have much for you. I have no history on the bike, bought it last October and I noticed it back then but I was more concerned with the cosmetics. Sat all winter fixing plastics and other things, didn't start driving it till June. If the bike stays cool it idles fine its not till it gets hot then the idle increases.

Thanx, Bill

 

Well , that sounds like it's rich at idle. Lean out the idle mixture a half turn or so and see what happens.

 

i had the same problem with my 1999 cbr 900......but it went all good after i cleaned the carb in general, took it out and used lots of carb cleaner after dissembling it...!! mine used to chug on first start of day at about 1200rpm and go to 1600 after heated up around 65-80 degrees and it was running ''FAT''..... now it starts (cold) at 1400 and goes to 1600 when heated up..!! i keep it to 1500 because i use yoshimura pipe...thanx...!!

 

Check your plugs out and clean the carbs really good. I was having all sorts of issues with my bike and plugs were the number 1 cause of it.

Also you said its been sitting for a long time? did you flush the tank and lines and put fresh clean gas in it?

 

get the carbs off of the bike and dont just spray them and put em back on!! take out te jets and inspect them for blockage, but you need to adjust your air fuel screws and make sure you set them at 2.5 turns out from a lightly seated position, then make sure your airfilter isnt dirty!! 900's like breathing clean air, but if you live above 3000 ft in altitude or ride in mostly that climate yo may want to try 3 turns out!! Then let us know how it works

 

how much did you say bro (toddmonster) ...2.5 turns or 3 i did it 5 when i last leaned my carb, will that interfere any thing or do any harm.....i have no idea about this air fuel mixture......???
check this video guys i made after cleaning carb and before cleaning......!! YouTube - honda cbr 900rr

 

first I would look into trying a different fuel. drain the tank and replace with fresh. locate a service manual and follow the instructions to set the carb mixture screws. you may alco want to check the choke is functioning correctly. lastly think about tacking the carbs off removing the bowls and seeing the condition inside the fuel area it will give you a good idea of how well it was maintained. while the carbs are outtake a look at what main jets are installed this will also indicate if there were modifications they may be causing your issue. If you check all that out sync the carbs set the mixture screws and checy the choke curcuit you will find your problem.. check for air leaks by checkng that carb mounting screws and the air box screws. there are three hex screws on the head that allows you to sync the carbs make sure they are in place and tight.

 

if your air screws are turned out 5 turns you are running way too lean and couls possibly drop valves as your bike is gonna run hot the exhaust will turn cherry red and then the exhaust valves will start pinging after that the problems will continue to snowball the efective range is from 2 to 3 depending what your running for intake and exhaust