I synced the carbs at 1000rpm and all seemed to be great (it isn't the riding season yet -10C temp out here). Then I looked at the air filter it looked too dirty so decided to change it. Now the engine "dies" when half-warm at idle speed and when I release the throttle after giving it some revs the revs don't drop as quickly as they used to. Am I having trouble with lean mixture?

 

u def have a lean condition, but it doesnt make sense if u only sync'd them. it most likely is the pilot circut, ie pilot jets, passages, and/or idle mixture. somewhere theres a missing puzzle piece in ur posts.

 

The new filter could make it leaner, but the idle speed can easily be turned up at the black plastic screw. As for the revs hanging up, the black plastic pistons that the needle jet attaches to, and/or the piston bores are dirty.

With the engine off, you can pull back the air box and stick a finger in the carb. Lift up the piston. It should go up with light resistance. Let it fall. It should fall with a soft plastic thump. Do all four. If one or all stay up or come down slowly, you have to take the carbs off and clean the upper part like this:https://cbrforum.com/forum/how-tos-8...needle-103846/ If one piston comes down with no resistance, you have a tear in the rubber diaphragm above the piston. Rubber cement will fix that.

 

The plastic pistons should be ok and the carbs clean. I cleaned the carbs few months ago and it hasn't ran much since then. The only thing that I didn't check when I cleaned the carbs was float level. I'll try to re-sync the carbs (maybe I didn't do such a good job as it was my first time) and if that doesn't help turn the pilot screw out half a turn.

 

Hi there vanalendur,
Were you able to fix your issue? I'm planning on sync my carbs as well. Also, thinking on cleaning the carbs on my 1990 CRB1000F. I've never done it either and I'm wondering if there is any heads up you can give me on both sync and cleaning the carbs. Thanks

 

Turned the pilot screws 1/4 turn more open and it seems to be OK now.