carbs

[oneday!]

i no this should be in tech but these carbs are really starting to piss me off, scat 35 twins, no matter what i do there is always black smoke and there is alot of shaken going on around tick over,i no that it seems like an air leak but cant find anything, the only time she nearly runs clear is when the mixture screws are wound rite in but i dont want to take that chance and cook the old girl, but shes fine on pick up i no these carbs i supposed to run on two cylinders at idle but why the shaking,didnt do it with my single carb, with these on her she really does fly along nice but sounds really dogy at tick over ive done the tappets points timing with gun maybe jetted wrong? :roll:

 

[Trikky2]

Its not an air leak. Black smoke = rich mixture. Air leak = lean mixture.

If its running on two cylinders it is probably the cylinders on the same side of the engine that are running rich and the prime suspect would be fuel level in the float chamber of the carb on that side.

Check the needle valve is shutting off correctly, the fuel level in the float chamber is correct.

If not then you may need to replace the needle valve or the float.

If the carb has been messed with then the washer between the needle valve and the carb top may be damaged/leaking or missing altogether, in which case the fuel level in the float chamber will be too high.

 

[oneday!]

nice one trikky will be delving into it but what about the shaking is this down to the same thing?
cheers
leon

 

[Trikky2]

Yes, the shaking will occur when one or more cylinders arent firing, because the engine will be out of balance eg. the inertia of the rotating bits being turned unevenly will cause the engine to "shake"