5 replies to this topic

[mini-mad-dan]

hi just wondering how many revs should my mini be doing with choke fully out? asd it seems to be 2500-2700 rpm (only for tiny bit as i set it back after a few seconds) but it is still at 2000 rpm at half choke is this right?

[fikus01]

i set mine to 2200rpm when cold at full choke, and let it sit at 1500 when its hapy to til the temp gauge starts to move then she's more or less happy to sit at no choke!!

[Bungle]

mine just adds another 500 rpm

[mini-mad-dan]

so full choke and i could get 1500(bungle) or 2200 im just thinking i should get it as low as possible to help prevent engine wear on cold start-up?

[Dan]

That is not how to set up the choke control on an SU carb properly. The SU choke control has two functions, the first 1/4 inch or so of travel is just a fast idle setting only, after that the rest of the travel enriches the mixture. You should just set the fast idle setting, the rest of the choke setting sorts itself out based on the needle. To do this on an HS design you need to hold the choke in the position where the linkage is about to start moving the jet down and set the fast idle speed to (ideally) 1600 rpm. To do it on an HIF type you need to hold the choke in the position where the arrow marked on the choke lever aligns with the adjusting screw (this is stamped on since you can't see when the fuel channel inside the carb is opening) and set the fast idle speed as above. The idle speed you get at full choke will vary depending on many things (fuel type, needle profile, engine size and type, cam, piston spring, dashpot oil, the weather.....) so set the carb up like it says in the manual and it will work properly. You can set a higher speed if you don't think it's working well enough but always set it in the correct setting position.

[mini-mad-dan]

i assume the 1/4 is the black part of the chocke knob, if so mine does absolutley nothing to the speed at all! well maybee 100 rpm (yes 100)