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Fao Mini Owners (and Anyone Who Knows Engines)


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Well i'm trying to get my Mini's engine happy enough for its mot tomorrow.

I've set the idle speed at around 1100 rpm and it seems happy enough to run at that speed and will accelerate nicely from there.

The main problem is that the exhaust is very loud and making black smoke. Its puffing slightly but not totally regularly. When i put the accelerator down it will make a puff of black smoke and then settle down.

I've pushed the piston up on the carb and the revs got quicker, so i did the nut at the base of the carb up against the spring, testing it every couple of flats. I've got the nut done up fully now, and the revs still increase when i push the piston up. Problem. There's too much fuel in the mixture so could it be a problem with the air supply? I've been tuning it without the air filter on, but putting it back doenst alter anything.

I'd like to check the valve clearances and the spark plugs but i dont have a feeler gauge, i think i might have to go get one this afternoon.

As always, any thoughts appreciated, as quickly as possible!

If i cant sort it i'll have to get my MOT garage to do it... :lol:

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First thing that came to mind when you said black smoke was piston rings. but you say that when you rev it, it smokes and then clears. so it may not be this.

Another that came to mind are the stem seals in your cylinder head are worn which is allowing oil into the chambers and burning on the intake. this isnt a major problem but you may not pass your mot on emmisions etc. if it is stem seals i would estimate £50-75 to get it fixed depending on where you go, obviously you should install a new head gasket at this point aswell. as for your tuning problem i am not to sure on what you should do. i would just take it to the mot station and let thyem have a twiddle. oh and you should tune your car with the filter onas the difference is noticable and it is all to do with air/fuel mixtures. you will be overfuelling if you tune it without the filter and then put it on because you are restricting the ar flow hence the air/fuel mixture will be too rich.

hope this helps


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Its impossible to get at the carb on a mini with the air filter on, so thats not a viable option.

You could well be right about the seals in the head, but i'm fairly sure its a probem with the mixture (the black smoke being unburnt fuel) so its probably a problem with the carb.

Will report back after the MOT tomorrow. :lol:

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Black smoke normaly means its running rich.

Oil normaly makes blue smoke.

You could try checking the float level, dont know what else to suggest, never had a mini, so dont know its carb.

Try checking the needles and that its all set correct.

Edited by 24seven
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Yeah, the problem is that i've adjusted the jet so its as lean as i can make it (all the way up against the spring) and its still too rich.

A mini friend has sugested that there's probably a problem with the jet and/or needle on the carb, but i can't fix that before tomorrow.

Any ideas for reducing emissions and improving the idle before the mot?

Thanks people :lol:

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