Engine dies twisting throttle

[tom1104]

Hello all,
I have an issue with my CB77. The bike starts up nice and easy, idles perfectly on both cylinders but as soon as I twist the throttle the engine dies. The only way i can rev the engine is if I very slowly turn the throttle and I mean very slowly. I'm guessing it may be a fuelling issue. Any ideas would be greatly appreciated. Recently ultrasonically cleaned the carbs/jets, timing and valve gaps adjusted, new spark plugs/caps, fresh fuel, new throttle cable, throttle valves are on the correct carb L and R

[deuce_7]

First check would be to insure the throttle valves rise and fall at the same time. Check the slot positions of the jet needles - same as before or if changed, why? Float bowl levels correct? Any fuel line flow restrictions from tank to carbs?

How did the engine perform before work was done, and was there a specific reason that carbs were disassembled and cleaned?

[tom1104]

Thanks for the reply,
I removed and cleaned out the carbs due to the bike running a bit rough when purchased. Turned out the o ring on the carb had disintegrated and gone into the carb, so i replaced that and the bike is running much better now when idling. It does idle great and I can ride it just about if I pull the throttle very slowly. I'll have a go at changing the position of the needle and see how that goes. Which notch is it standard?

[deuce_7]

Start with middle notch on the needles. Also, the carb jets degrade with time and wear. Consider replacing them if not already.

This forum has a good search capability. Did a search for "needle" and found: search.php?st=0&sk=t&sd=d&sr=posts&keyw ... 12&start=7

You can narrow search with key words to find results with more precision.

[tom1104]

Thanks, I'll have a read. I did try changing with the needle position a few days back. It was on the middle and I lowered the needle, so placed the clip one up from the middle. I'll give a go on all the other positions and see how it goes

[deuce_7]

Lowering needles will lean the mixture. Raising needles will provide a richer mixture. Engine might be starving for fuel at higher RPM, so raising needles could provide a clue.

[sky.fred]

There may also be an air intake.
With the engine running, spray water on the carburetors. If the rpm drops or the engine stalls, there's an air intake.