Gets a little rough at 6500 RPM
 

Hey guys so I just got my bike on the road after it sat for a bit and it runs real well around the town but when I take it on the highway, once I start gunning it and get up to about 7k rpm, it starts to putter a bit and doesn't really get any faster. I have sprayed carb cleaner down the carbs when they were off but I never took the carbs off one by one to do so.

I just replaced the switch on the fuel pump and it seems to work good.

Will using injector cleaner in the tank eventually work?

Just want to know what the common things to look at first before I spend a day taking her apart!

if your carbs are real gooey then best bet is a carb cleaner bath or the guy who builds my race engine says bath in diesel then clean off with carb cleaner, if green and crystaline substance then dirty and need a clean.

in this order check-
air leak at carb boot/ram air/ air box
fuelling to the carb T piece make sure lots of fuel is in there
carb slides move freely
float bowls and floats clean
jets are clean


sounds to me like too much air or not enough fuel through the main jet, shouldnt be pilot jet as it works low down.

Hey just so you know, Its good till like 4th gear. 1st 2nd and 3rd are good all the way through its only when it gets up to 4th and above. The bike is also having trouble starting if it sits for more then 5 hours. I just shoot some starter fluid in intake and start it up that way and it works perfect. Any ideas?

yeah i put restrictors in my carbs (uk law at 17) to produce on 33bhp the bike would red line in first and second but no other gears. this tells me that your cylinders aren't getting the appropriate mixture.

clean the carbs thoroughly dead easy job if you go deep clean start on friday night soak the jets over night and rebuild saturday morning, check moving parts move etc and get back to us after the carb clean.

is there a video or tutorial on how to clean them?

All the input you need, courtesy of IdoDirt

https://cbrforum.com/forum/stickies-...cation-124026/

Ride safe,
Ant.

I like that post but is there anything more detailed? I really dont want to mess it up worse then it already is.

Thanks for the help man

you wont mess it up just take off carbs

remove float bowl and jets soak them in carb cleaner over night then scrub with tooth brush and compressed air

take the slides out and clean with brush and carb cleaner

the hardest part i found was getting the gasket in the correct place so it didnt get pinched but you can use a small amount of yellow grease to hold the gasket in place.

Help!
 

Okay I did all that and it runs much better but still does it!!!! Is it running too lean maybe or maybe its not getting enough fuel at high RPM's? I did the air bypass as well. The only thing I didnt clean was the jet needle holder.

The jets are 136's and 138's. The previous owner had the jets meesed it with (going from 1-4) 136, 138, 136, 138's and I put it back to factory with 138's on the inside. The pilot jet is turned out to 2.5 and I have a K&N and a undertail exhaust.


The bike runs AMAZING in low rpms and high rpms in first 3 gears but then 4th-6th after 6500 rpm it starts to stutter. HELP!!!!

so everything is working as it should carb wise? well im a little stumped with this one my next guess would be that the undertail exhaust is lowering back pressure making your engine flow quicker which would mean it needs more air or more fuel or both, i would go to a dyno any decent dyno tech will have your bike running at peak power within a few hours i had mine setup correctly for £160