Hi,

I have a 91 CBR 600 that was sitting for a year and would not start. I drained the tank and put in fresh gas then had to clean the carbs out. The bike start and runs at all speeds now, however, when I apply throttle it is slow to return to idle. I know that the rubber diaphragms were ok on the needle sliders when I disassmebled. This is my first carb cleaning, so I'm not sure what to do next.

thanks

 

When you put it all back together by any chance is the throttle cable somehow hitting the choke cable a little bit or the choke sticking?if not what about the needle screw how many turns out did you put that screw out in the carbsi put my 91 to about 2 1/2.

 

isn't factory 1.5 turns from the bottom for the pilot screw

 

This can be an indication that the engine is getting air past the carbs that is the rubbers between the carbs and the cylinder head may be bad. One other thing is fuel mixture, if it is way to lean this can happen. At what RPM will this problem start ?

 

I think the cables are ok. I backed out the pilot screws two turns.The Rubber for the intake ports seemed ok, but the whole assmbly took some force to get on and seat properly.

One thing that Iforgot tomention is that the small foam air filter (not sure what it is called or what it does) that is attached to the hose going to the carb body is missing. Would this cause too much air? Is this a breather mechanism of some sort?

 

HeyVallip,

The problem seems to be on the lower end of the rev range. If I opened up the throttleto say 7k or so then letoff it seemed to linger at around 3.5-4k and would take a long time to return to idle.

thanks

 

Ok if you are sure it is not the rubbers then I am leaning towards the pilot screws, try turning them 1/4 turn each time and see if that works, obviously there is a limit to how much you turn them out roughly 31/2 turns.

One thing you can dois take out a spark plug take a photo of it and post it, judging theA/F ratio from a photo is not the best but we can give that a try.

 

here is a pic of the #1 cylinder plug. Pic is a bit fuzzy, but the tip was covered in a white clky powder that I could wipe off, the rest of the plug looked normal. These plugs were new and only had 15 or so miles on them.

[IMG]local://upfiles/29074/4945900C622248DA9318555FA7914B66.jpg[/IMG]

[IMG]local://upfiles/29074/B7536FE3FAF54A16879D041F04D1924B.jpg[/IMG]

 

Download the service manual and follow the instructions for adjusting the pilot screws.

The starting point is approximately 1.5 turns, but can end up being more or less after adjustments are done.

 

Hi there,

now as you say the photos are a bit fussy and difficult to read but it seems that the steel tip ( the bent part coming from the outside of the plug ) is a bit white, correct me if I am wrong, and that tells me that the bike is not getting sufficient fuel during idling. Have you tried turning the pilot screws out ?