Trouble setting up the carb on 803cc SII - Help!

[damian1978]

Hi, I've recently removed the carburettor on my 803cc SII to replace some cork seals round the jet. I got a repair kit from Bull Motif and I've replaced the jet and the rubber seals. The old ones were leaking.

The choke seems to operate smoothly now and the leaking is cured. The car does in fact run ok, but I'm concerned as to whether the mixture is set correctly as the car doesn't always idle at the correct speed. I've adjusted a screw on the side of the carb whilst the car was idling and that seemed to work, but occasionally it idles to fast.

Does anyone have any ideas? I'm not very knowledgeable on carbs and I've done this 'blind' so far, so to speak.

Any advice appreciated!

[mike.perry]

First warm the engine up and push the choke control knob fully in.
The mixture adjusting nut is the big brass nut with the spring above it under the carb. Mark one flat of the nut with Tippex so you have a reference point. Wind the nut fully up. Next wind the nut down two complete turns or 12 flats. This will give you a starting point. Wind the nut up or down a couple of flats at a time until you have the fastest tickover. This will give you near enough the correct mixture setting.
The two screws on the side of the carb are for setting the idle speed. The one that contacts the moving cam governs the choke control fast idle speed and should be adjusted so that it is just touching the cam. The other one controls the engine tickover speed and should be adjusted after the mixture nut has been set.
Order of adjustment
1. Adjust screw away from cam.
2. Set engine tickover speed to as slow as possible without stalling the engine. You may have to readjust this screw whilst you are setting the mixture to prevent stalling
3. Set mixture adjusting nut to fastest / smoothest tickover
4. Readjust tickover screw to desired engine speed
5. Re adjust other screw to just touching cam.
It sounds complicated but ensures that adjustment of one screw does not affect the other settings.
When you pull the choke lever out the first part of the movement turns the cam and increases the tickover speed, the rest of the movement pulls the central jet down and richens the mixture for cold starts.

[damian1978]

Thanks for that Mike, it looks a really comprehensive set of instructions. I'll give a go tomorrow when I'm off work. Hopefully things will turn out ok!

Thanks again.
Damian

[bmcecosse]

You also need to make sure the accelerator cable isn't sticking, and has a little slack when it's at the idling position. If it's not been renewed in the last few years - this may be the time ! You can use the inner cable from a bicycle gear shift - cost about 60p in bike shop!

[damian1978]

That's a good point actually. The cable is the same one which was on the car when I bought it 5 years ago and prior to that it had lived in a barn for years. I think I'll get one ordered. Thanks!

[bmcecosse]

Walk in to bike shop and buy the gear cable - it's fine !

[alanworland]

I found one bike cable was enough to replace accelerator, choke and starter switch pull (which was quite badly frayed) - great value!

[bmcecosse]

Certainly a handy spare to carry in the car.