19 replies to this topic

[BaronVonchesto]

I'd say the Throttle Disc isn't 100% centred. You won't be able to feel for it, during a build, I hold them up to the light to check them. It only takes the smallest of gaps. If it's been driven for a while like this, the throttle disc can 'eat' in to the body of the carb around the throttle disc, so check for that when you have it off.

If you suspect it's a worn spindle, there's a few ways to check for that. Spray some carb cleaner (or similar) around the ends of the spindle and see if the speed picks up further, of put some light grease around the ends to see if t slows it down. It would need to be pretty bad though to give a continuous high idle, they usually cause an erratic idle.

 

I suspect this is likely the case. Perhaps the disc isnt properly centred. If the disc eats into the carb body does that mean the carb is ruined?

[Spider]

I suspect this is likely the case. Perhaps the disc isnt properly centred. If the disc eats into the carb body does that mean the carb is ruined?

 

 

Usually, yes.

[MiNiKiN]

Have you checked the idle timing?

Two fools one thought.    I just was about to ask if he maybe has considerably advanced the ignition by accident. Mine was doing exactly that on initial start up, turned out the, not yet fastened, dizzy was set to +30 deg. 

[Dashpot Dad]

Did you centre the jet after the rebuild? If not then the needle could be fouling against the side of the jet and stopping the piston falling fully to the bridge.

[BaronVonchesto]

just came back to say that Spider was bang on the money. The disc wasn't properly centred when I rebuilt the carb. Thankfully the carb body wasn't badly scored. After centreing it properly, its working properly now.