7 replies to this topic

[Dutchy1990]

Good Evening All,

I’m having a few problems with the engine struggling to run at idle and struggling/lacking power on acceleration.

I thought I would adjust the idle speed and mixture on the carb but I can’t find the piston lifting pin To adjust the mixture correctly. Having looked through google for hours now I am no wiser on whether it should have one or not. If it should have one, can I get this part separately or will it have to be a new carb?

Apologise for the daft questions and thanks for any advice.

Cheers

[Maccmike8]

Mixture is the hex head under the carb and the idle adjustment is the cross head next to the throttle cable.

Make sure you have some engine oil in the carb top.

[Chris1275gt]

Not all hs4 carbs have a lifting pin my 75 car didn't have one but a second hand one I bought did. I don't think you can fit a lifting pin retrospectively. Get your hands on a colour tune plug and you'll be able to get the mixture very close without the expense of getting it on a rolling road.
This is a very easy book to to set up your carburettor eBay always has some for sale.

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Edited by Chris1275gt, 02 August 2021 - 08:29 PM.

[Dutchy1990]

Thanks for all the help.

[Richard_]

My mini us the same year and has no lifting pin. You can still lift the piston to help with tuning it as described here;

 

How To Tune Hs4 Carb Without Lifting Pin? - Problems, Questions and Technical - The Mini Forum

 

- but I'm a big fan of Colortune myself.

[sonscar]

They say that most carb problems are electrical.Make of that what you will.I never adjust the carb in isolation as you could be trying to mask other things.Service items are cheapish and provide a good baseline.(I also keep all changed items until the new items prove themselves)

I have a colourtune but find it of little use on varialble ventuari carbs such as SU as they assume everything is standard 1980s and in good order.Steve..

[richmondclassicsnorthwales]

Is this or was this a constant problem ?

 

What I mean is, why are you focused on the carb ?

 

Who directed you to look at the carb and nothing else ?

 

What year Mini do you have ?  Plugs, points, HT leads, dizzy cap, rotor arm, air filter, vacuum pipes, condenser, compression, these all play a part too

[Steam]

Check and set the timing first and verify all ignition amd timing are correct before assuming mixture is the fault or adjusting carb.
The su hs4 is a reliable carb usually let down by ignition faults.