24 replies to this topic

[Marc13]

Hi my classic Mini runs terribly when cold.

Starts fine every time. When stationary and you slowly press the accelerator the revs increase, but doesnt sound right. When stationary and you floor the accelerator it just dies, the revs drop away completely.

On the move when cold, its awful, actually sounds like its missing and is quite juddery.

Once its been driven for 4 or 5 minutes, it runs fine. Any idea on what can be done to sort the problem?

[sonscar]

More use of the choke?Steve..

[cal844]

Try a little more choke and also make sure you have the correct grade and quantity of dashpot oil for your car

[D 'n A]

Check for the adjustment of the choke at the carb in general.

When it runs maybe adjust the CO value to what the engine likes better?

[MatthewsDad]

Are any of the plugs fouling?

[bpirie1000]

Deafo a mixture issue i think....

[Marc13]

To answer a few points. The choke makes no difference - I can give it no choke, or full choke and it still runs like a pig when cold.

Plugs seam fine.

What is the correct grade and quantity of dashpot oil?

Regarding the mixture - isn't the mixture (adjustable by the screw on the carb) only applicable to the idle mixture? And when driving its the needle that controls the mixture, not the screw on the carb? Have I got that right?

Bit of a newbie here.....so what is meant by
"Check for the adjustment of the choke at the carb in general.

When it runs maybe adjust the CO value to what the engine likes better?"
Could you give me a bit more guidance on the above two points please?

Had the car out again today and its most definitely apparent when cold, either running or stationary....its awful and the more accelerator you give it, the worse it is

[D 'n A]

Oil level should be 6mm from the top if I'm not mistaken.

Regarding the choke setup: check that is actually moving the tube where the needle sits in downwards. If pulling your choke cable does not adequately move the parts in the carb you are not really using the choke.

You can also take off the dashpot and check if the tube of the needle sit slightly lower then flush with the carb body.this is a good starting point.engaging the choke should lower this pipe. Maybe also check what needle you have its stamped on the top side.

If pulling the choke gives no difference compared to no choke something is stuck open or base settings are way off.
That or an possible airleak of the carb. You can check this by spraying wd40 on the carb when the engine runs and see if the revs change.

The CO part is not important for now, first let it get to idle correctly

[D 'n A]

Also, are you sure your ignition is ok? Good leads? Clean distributor cap? Good ignition timing settings?

[D 'n A]

Also, are you sure your ignition is ok? Good leads? Clean distributor cap on the inside? Good ignition timing settings?

If you cant check the last, army least check if the distributor is not lose and can't be turned around by hand

[MatthewsDad]

SU carbs have a workshop manual, and they also have helpful technical notes on their website. Worth buying / downloading.

[cal844]

Your carb dashpot would have used 20w50 engine oil from the factory. Its what I've used on all my minis and I've never had an issue.

[Aaran13]

Your carb dashpot would have used 20w50 engine oil from the factory. Its what I've used on all my minis and I've never had an issue.

Agree with this. Rebuilt my SU for the 1st time recently and used the SU Oil, ran terribly. Replaced with 20w50 and made a huge difference.

[Marc13]

Oil level should be 6mm from the top if I'm not mistaken.

Regarding the choke setup: check that is actually moving the tube where the needle sits in downwards. If pulling your choke cable does not adequately move the parts in the carb you are not really using the choke.

You can also take off the dashpot and check if the tube of the needle sit slightly lower then flush with the carb body.this is a good starting point.engaging the choke should lower this pipe. Maybe also check what needle you have its stamped on the top side.

If pulling the choke gives no difference compared to no choke something is stuck open or base settings are way off.
That or an possible airleak of the carb. You can check this by spraying wd40 on the carb when the engine runs and see if the revs change.

The CO part is not important for now, first let it get to idle correctly

[Marc13]

Oil level should be 6mm from the top if I'm not mistaken.

Regarding the choke setup: check that is actually moving the tube where the needle sits in downwards. If pulling your choke cable does not adequately move the parts in the carb you are not really using the choke.

You can also take off the dashpot and check if the tube of the needle sit slightly lower then flush with the carb body.this is a good starting point.engaging the choke should lower this pipe. Maybe also check what needle you have its stamped on the top side.

If pulling the choke gives no difference compared to no choke something is stuck open or base settings are way off.
That or an possible airleak of the carb. You can check this by spraying wd40 on the carb when the engine runs and see if the revs change.

The CO part is not important for now, first let it get to idle correctly

How do i check that the choke is moving the tube near the needle?

How do i check if the needle sits slightly lower than the carb body?

Wheres the stamp - the top side if what?

Im sure the choke is doing something, when i pull it right out, you can tell the revs are changing. But floor the accelerator and it just loses everything - the same as with little or no choke.

You say "If pulling the choke gives no difference compared to no choke something is stuck open or base settings are way off."
It gives difference, ie the revs increase, but it makes no difference to the fact that the engine almist dies if you press the accelorator hard.

Leads/ignition/timing/distributor all fine. Changed a lot of these parts and had timing done not long ago.

If there was an air leak, by spraying carb with wd40 you would really expect revs to increase?? I'll check tomorrow or sunday

Thanks for all the help and sorry for all the questions