9 replies to this topic

[Murrayup]

I think the settings are correct on this hs4 however the engine only runs on 3/4 choke and not smoothly. Hunting etc. I suspect an air leak on manifold gasket.
1973 998cc mini clubman.
Was waxstat
New mechanical fuel pump.
Mixture adjusted 2 turns down from flush jet on bridge.
Red jet tube and AAC needle.
New float seat and needle.
M/S gold coil new
M/S electronic distributor geu390ms new
M/S plugs leads and cap new
Any other reasons for poor running greatly appreciated
Regards Ian.

Attached Files

•  IMG_4047.jpeg   72.82K   5 downloads

[68+86auto]

Can you post a picture of the other side of the carb?

[timmy850]

Setting the mixture 2 turns down is just a starting point to get the engine running. You will likely need to measure the idle mixture and set it correctly for your specific engine (once it’s up to operating temperature).

Have you set the correct idle speed?

If you suspect a gasket leak you can test this with brake clean or a similar product, spray it carefully around the suspect areas and see if the engine changes in rpm. Replacing the manifold and carb gaskets will allow you to check a few things while it’s apart

[68+86auto]

A waxstat carb apparently has a finer thread so would need more turns.

Edited by 68+86auto, 22 April 2026 - 05:55 AM.

[Murrayup]

I have a new gasket coming today as well as new studs washer and manifold nuts.
I did the brake and clutch spray test and I think there was a momentary rise in revs.
Difficult to tell as the engine revs are all over the place below 2000 rpm.
Set the ignition timing visually with rotor pointing at no1 cyl with 7&8 rocking.
Regards Ian.

[68+86auto]

I have a new gasket coming today as well as new studs washer and manifold nuts.
I did the brake and clutch spray test and I think there was a momentary rise in revs.
Difficult to tell as the engine revs are all over the place below 2000 rpm.
Set the ignition timing visually with rotor pointing at no1 cyl with 7&8 rocking.
Regards Ian.

 

Setting the timing using the rotor position isn't sufficient.

[Murrayup]

This is the Su hs4 other side as requested.
Regards Ian.

Attached Files

•  IMG_4048.jpeg   66.83K   4 downloads

[Chris1275gt]

Is the choke out in the first picture? If not the jet isn’t hard up against the mixture nut as you have what looks like a 3-4mm gap

[Murrayup]

Second photo: not sure re choke but your right it’s not up against the nut.

Attached Files

•  IMG_4047.jpeg   72.82K   5 downloads

[Ethel]

The choke cam is a bit past the fast idle position if that's as far as it returns with the choke in.