Float Bowl Adjustment

Posted by Myumi-2 on Apr 20, 2009; 7:40am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Float-Bowl-Adjustment-tp459762.html

I'm progressively working through the issues with my 1972/74 CB750 and each solution unearths another problem on the path to ideal performance.  

The most recent issue is when operating at between 3000 and 4000 revs the performance is unsteady.  The bike feels jittery as if one cylinder is only sparking occasionally.  i.e. when maintaining a constant speed of 60kms/hr it will gradually slow down, then when I increase the throttle slightly, it will come back to life with gusto and rapidly accelerate to 70km.  If I change down a gear and maintain a constant speed of 60km/h with 6000 revs there are no performance issues.  

Also when acclerating slowly from a standing start there is a pause, right at the start of the acceleration, before the engine kicks in with full power.  Whilst under hard acceleration is problem is not apparent.  

Whilst the immediate solution might appear to be that I just need to ride this bike hard and keep the revs up, I'd like to resolve this little problem.

I suspect that the issue is Carb related.  Ive had a series of events with my number 3 carb.  First, it was overflowing (I adjusted the float), then it seemed to develop a bloakage and no fuel was making it to the bowl (I was able to fix this on the side of the road by removing the fuel line from the tank and blowing through the line). So tonight I'm going to pull the carbs out again and clean them, re-sync and see what the outcome is.

Ive cleaned the carbs before, I've not re-jetted as they appear fine, and synced the carbs with noticable improvement.  

I have a suspicion that I may have over compensated for the overflow problem and adjusted the float bowl to far causing the one jet to be starved of fuel at speeds.

My question is what is the correct adjustment/height for the float?

Cheers
Tim