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Hif38 Carb Running Lean


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#1 sschewie

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Posted 29 January 2011 - 04:59 PM

Hi, I've recently bought a Hif38 carb and fitted it to my 1275. It seems to run ok, but if i push the pin to lift the piston up, it stalls. What i can't understand is why this happens as the mixing screw is screwed in all the way (full rich). I thought if it stalls it's running too lean? Does anyone know what's wrong with it?

#2 tommy13

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Posted 29 January 2011 - 05:55 PM

Pushing the piston lifting pin right up will cause the engine to stall. The piston should only be lifted by 0.8 mm when using it to set the mixture. I always find this difficult to do and it is sometimes easier to insert a small screwdriver into the mouth of the carb and twist it to lift the piston just a little.
It should be possible to to get the mixture roughly correct by screwing the mix screw in and out to get the fastest consistent idle point. If you still think its not rich enough, check for air leaks.

#3 bmcecosse

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Posted 29 January 2011 - 05:58 PM

Yes - adjust to get smoothest idle - but an HIF 38 is really too small for a 1275 anyway - you want an HIF 44 for best performance.

#4 AVV IT

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Posted 29 January 2011 - 07:04 PM

What sort of 1275 are you running, a HIF38 is adequate for a standard engine & was fitted to the late non cooper 1275's as standard. But if you are running a cooper or MG metro unit, then as suggested above a HIF44 is really what's needed. You might also want to consider a richer needle, particularly if you have any air flow mods such as a high flow air filter, gas glowed manifolds or performance exhaust etc.

#5 sschewie

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Posted 30 January 2011 - 12:09 PM

What sort of 1275 are you running, a HIF38 is adequate for a standard engine & was fitted to the late non cooper 1275's as standard. But if you are running a cooper or MG metro unit, then as suggested above a HIF44 is really what's needed. You might also want to consider a richer needle, particularly if you have any air flow mods such as a high flow air filter, gas glowed manifolds or performance exhaust etc.



I'm not sure. I bought it from a guy locally who stripped it out of a car he had aquired. As the car is still in building stage, i haven't actually driven it yet to see how well it goes. I think it may have had some tuning as the engine number has been machined off the block. I want to remove the head sometime and measure the pistons to find out what it really is.

Going back to the lifting pin, it sounds like i'm at fault by pushing the pin too far! :D
I'll have another go when i get the chance to see what 0.8mm does.

Thanks for your replies guys. :D

#6 Jon Hunt

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Posted 30 January 2011 - 09:03 PM

I am in a very similar position. Bought my first mini just over 2 years ago and still trying to get to grips with the exact spec of what I have. It is a 1275 MG Metro but like you with a HIF38, and yes even with the mixture quite rich, even the slightest raising of the piston causes it to still. Colour tune (which I know isn't that accurate), give indication of worn needle. We passed the MOT back in Dec with no problems, running ok at the moment but you always have that thought in your mind it could be better.

It does have a pancake type K&N filter and non standard exhaust but original exhaust manifold. It's a bit of a mish-mash, but after discovering only last week it was an MG Metro engine I can at least set the valve clearance to what they should be.

I'd be interested to see if you get the HIF38 behaving as it should. In the meantime I'll be looking for a HIF44, although apparently my father in law has a pair of twin carb down in his shed....somewhere?

..but from I've read on the mini forums that i regularly trawl, the only way to get right is on a rolling road.

#7 bmcecosse

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Posted 30 January 2011 - 09:10 PM

No need to fuss with a rolling road for such a simple engine. The MG Metro should have the HIF 44 - with BDL needle. Simples. Forget the twins ! Enlighten me please - what gaps will you set at the valves????

#8 Jon Hunt

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Posted 30 January 2011 - 09:29 PM

My budget wouldn't stretch to a rolling road session, so till now I've been using a variety of methods with just a timing strobe, exhaust note on idle, spark plugs and generally how it drives.

Without a Haynes on the MG Metro, guidance I've read is 13 thou on inlets and 16 on exhaust.

The big difference is also as it's most likely unleaded and that I'm using Valve Master, should help slow down any addition wear on the seats and constant adjustments.

...but still learning, so happy if anyone has some advice.

#9 bmcecosse

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Posted 30 January 2011 - 10:06 PM

These gaps are fine - don't bother with additives......... Just check/reset the valve gaps every 3000 miles.




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