Su Hs4 Carb Set Up.

hey all, having a few probs setting up my carb. the engine runs and idles sometimes but then on its own the revs go up and down by them selves. and when i press the throttle pedal it isnt what i would call efficient, the revs go up but take ages to come down when i release then pedal. heres a picture of my set up. help would be greatly appreciated. cheers callum.

Have you topped up the dash pot with oil. The throttle will not return without the dashpot oil pressure to assist the spring.

yeah the oil is topped up.
red ones the accelerator and blacks the choke.

I notice a couple of things -

* Your choke looks like it's not adjusted correctly - when the choke is not in use the screw should not be in contact with the heel of the mechanism.
the choke does 2 things in a particular order - the first half of it's travel will lower the jet, the second half of the travel should open the throttle a small amount.

* Have you made sure the throttle cable has a tiny amount of slack on it? If you have pulled it tight so the pedal is all the way up when your foot isn't on it, then the throttle will not be able to close fully under the weight of the pedal etc,.. this can hold your idle up,... in addition to what i mentioned before, the choke screw looks like it's stopping the Throttle closing up properly for idle

other than this - check for air leaks around the carb, all the gaskets okay?

I notice a couple of things -

* Your choke looks like it's not adjusted correctly - when the choke is not in use the screw should not be in contact with the heel of the mechanism.
the choke does 2 things in a particular order - the first half of it's travel will lower the jet, the second half of the travel should open the throttle a small amount.

* Have you made sure the throttle cable has a tiny amount of slack on it? If you have pulled it tight so the pedal is all the way up when your foot isn't on it, then the throttle will not be able to close fully under the weight of the pedal etc,.. this can hold your idle up,... in addition to what i mentioned before, the choke screw looks like it's stopping the Throttle closing up properly for idle

other than this - check for air leaks around the carb, all the gaskets okay?

right many thanks mate i have printed out what you have said and i will go and check it all and adjust it all. all the gaskets are brand new.
callum

Sounds like sticking throttle cable - fit a new one ! The comments the other lads have made are all relevant too - except the dashpot oil does NOT help close the throttle................

throttle cable already new.

I'm having a similar problem with my twins,

recently rebuilt and a new cable yada yada yada.

Recently all of a sudden the throttle is really slow to come down, sometimes sticking. The cable is not sticking in the outer as it is the same when I open the bonnet and force the butterfly closed by hand. It stuck at 3.5k rpm coming off the M5 into a service station much to everyones horror! a quick blip of the throttle clears it though and it fell back to idle, but very slowly.

I have a slight air leak due to a worn spindle and have believed this to be the cause.

Edited by AlexP, 21 June 2010 - 01:38 PM.