At The End Of My Tether... KAD 1380 Road 100 & HIF44

[Exminiman]

Duplicate please delete - Sausage fingers…..

[Peter Laidler]

Reading through this saga again, surely this is a problem that could be identified with an old COLOUR-TUNE. I still use a pair of them when needed. In addition to the needle bodgery/butchery that we can see, it is a volumetric air/fuel mix problem across the whole range problem. NOT a difficult problem to fix I say. And as soon as I read the words 'filter king'..........

[Exminiman]

Maybe the needle was mangled from the start ?

“ From cold it would start (no choke) but would not idle without constant throttle input - any choke and it was flooding. Once warm it would idle anywhere between 1200 and 1500.”

Surly the needle would let lots of fuel past it in that state…it’s almost squared off

[Peter Laidler]

You're dead right Marc. At the point where it's butchered, closest to the piston, is (virtually) at tickover, allowing too much fuel through. Trying to do anything else while retaining that needle is doomed to failure.

Take exminimans advice on board Marcos-craig and you're on the home straight to fixing the problem.

As I keep saying, carburation is not difficult in itself but it is a practical thing......, more a seein' and doin', practical thing as opposed to a readin' about it thing. It's not even taught to apprentices now and very soon, I fear it'll become a forgotten art, like listening to the different sounds made by air intakes as they draw cleanly - or struggle for breath as we used to say

[Marcos_Craig]

EDIT Just an after thought, are you sure the needle was mangled by KAD, and not by the Bradford specialist ?


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Yes, I’ve had it confirmed from the guy who built the engine. Apparently done to set the “correct” progressive air fuel ratio.

[Marcos_Craig]

You're dead right Marc. At the point where it's butchered, closest to the piston, is (virtually) at tickover, allowing too much fuel through. Trying to do anything else while retaining that needle is doomed to failure.

Take exminimans advice on board Marcos-craig and you're on the home straight to fixing the problem.

As I keep saying, carburation is not difficult in itself but it is a practical thing......, more a seein' and doin', practical thing as opposed to a readin' about it thing. It's not even taught to apprentices now and very soon, I fear it'll become a forgotten art, like listening to the different sounds made by air intakes as they draw cleanly - or struggle for breath as we used to say

Like Goff said, it is now sorted thanks to AC Dodd. I could not agree more about it becoming a forgotten art. AC is a wonder to watch, and you can hear the results between every profiling of the needle. I could not recommend his services highly enough.

[Allen Brzeczek]

I have a 1380, self assembled - MED machining/supplied. I am using twin 1.5" SU's. Fires up quite quickly but needs full choke then part choke until engine is warm. I suspect that in keeping with many other vintage car owners I use a clothes peg to hold the choke until the engine is up to temp.

With lightened and balanced crank/flywheel together with choice of cam tick-over is somewhat lumpy therefore I choose to set this somewhat higher than normal.

[Desmodromic]

+1 on the clothes peg for choke duties! Should be standard issue.

Though I only have to use it with H4 or at least H series carbs, the HS series chokes don't seem to need one, as the return spring mechanism is different.

[burchy35]

The peg is a must. My peg clips onto the heater switch panel when not used for the chock which stops the heater panel from vibrating.
Shame there are no pegs with Austin mini printed on them.
They would fly off the shelves

[Desmodromic]

The peg is a must. My peg clips onto the heater switch panel when not used for the chock which stops the heater panel from vibrating.
Shame there are no pegs with Austin mini printed on them.
They would fly off the shelves

A BMC Special Tuning peg for those with twin H4's really should exist

[timmy201]

There’s some people doing custom choke pegs
https://www.ohsoretro.co.uk/product/choke-pegs/

[burchy35]

Bloody fantastic, that is going on my good boy xmas list.

[850man]

Some of the responses in this thread are unbelievable. You would think that a number of people on this forum have never actually tuned a Mini or worked on a SU carburettor before.

1st, Tell me, why is the float bowl breather blocked off?

2nd, Anyone who thinks that modifying a SU needle to obtain a better mixture clearly does not own an SU needle chart or a stockpile of needles to choose from. There are hundreds of needles available, there is no need to ever modify a needle. That's just poor workmanship and outright laziness. AND it has nothing to do with this carburettors cold start problem.

3rd. Jet size, needle type, Dyno sessions, etc have nothing to do with cold startup, while using the choke.

I stood at the 2019 IMM watching a well known "expert" tune peoples Minis under a tent. I had to walk away because I could not believe what I was seeing.

[timmy201]

I guess it depends if it’s the fuel bowl breather or the crankcase breather port. It’s not clear from previous messages

[Exminiman]

Some of the responses in this thread are unbelievable. You would think that a number of people on this forum have never actually tuned a Mini or worked on a SU carburettor before.

1st, Tell me, why is the float bowl breather blocked off?

2nd, Anyone who thinks that modifying a SU needle to obtain a better mixture clearly does not own an SU needle chart or a stockpile of needles to choose from. There are hundreds of needles available, there is no need to ever modify a needle. That's just poor workmanship and outright laziness. AND it has nothing to do with this carburettors cold start problem.

3rd. Jet size, needle type, Dyno sessions, etc have nothing to do with cold startup, while using the choke.

I stood at the 2019 IMM watching a well known "expert" tune peoples Minis under a tent. I had to walk away because I could not believe what I was seeing.

So what do you think the problem was or is ?

['S'-type]

Some of the responses in this thread are unbelievable. You would think that a number of people on this forum have never actually tuned a Mini or worked on a SU carburettor before.

1st, Tell me, why is the float bowl breather blocked off?

2nd, Anyone who thinks that modifying a SU needle to obtain a better mixture clearly does not own an SU needle chart or a stockpile of needles to choose from. There are hundreds of needles available, there is no need to ever modify a needle. That's just poor workmanship and outright laziness. AND it has nothing to do with this carburettors cold start problem.

3rd. Jet size, needle type, Dyno sessions, etc have nothing to do with cold startup, while using the choke.

I stood at the 2019 IMM watching a well known "expert" tune peoples Minis under a tent. I had to walk away because I could not believe what I was seeing.

Quite a few of the responses on this thread did point towards the needle being the issue. Though nobody would have expected to see the butchery that turned out to be the cause of the OP's problem.
Should it have been spotted earlier? Probably. Should it have been sold like that? Probably not.

On point1, as Timmy says, we don't know which breather was blocked. I suspect the OP meant the crankcase breather.

On point 2, I agree that it should be possible to select the appropriate needle without modification. I doubt many shops carry 600 plus needles however. I agree a dyno session has nothing to do with a cold start, but once that problem is eradicated, surely that is the only way to be certain of how any particular needle is performing in any particular motor.
As regards the dark art of reprofiling, David Vizard was not averse to modifying needles as per his numerous publications. AC Dodd, not only found the problem but appears to have, through a process of modification, achieved very satisfactory results. The OP is happy. QED.

On point 3. I agree jet size/ needle profile have nothing to do with cold start up, while using the choke. But they DO when the car starts cold with NO choke and floods. This was the OP's main problem ( among others), which is why quite a few posters focussed on it being a needle/jet issue. With the benefit of hindsight, we now know that this was the correct diagnosis.

[Marcos_Craig]

Some of the responses in this thread are unbelievable. You would think that a number of people on this forum have never actually tuned a Mini or worked on a SU carburettor before.

1st, Tell me, why is the float bowl breather blocked off?

2nd, Anyone who thinks that modifying a SU needle to obtain a better mixture clearly does not own an SU needle chart or a stockpile of needles to choose from. There are hundreds of needles available, there is no need to ever modify a needle. That's just poor workmanship and outright laziness. AND it has nothing to do with this carburettors cold start problem.

3rd. Jet size, needle type, Dyno sessions, etc have nothing to do with cold startup, while using the choke.

I stood at the 2019 IMM watching a well known "expert" tune peoples Minis under a tent. I had to walk away because I could not believe what I was seeing.

Quite a few of the responses on this thread did point towards the needle being the issue. Though nobody would have expected to see the butchery that turned out to be the cause of the OP's problem.
Should it have been spotted earlier? Probably. Should it have been sold like that? Probably not.

On point1, as Timmy says, we don't know which breather was blocked. I suspect the OP meant the crankcase breather.

On point 2, I agree that it should be possible to select the appropriate needle without modification. I doubt many shops carry 600 plus needles however. I agree a dyno session has nothing to do with a cold start, but once that problem is eradicated, surely that is the only way to be certain of how any particular needle is performing in any particular motor.
As regards the dark art of reprofiling, David Vizard was not averse to modifying needles as per his numerous publications. AC Dodd, not only found the problem but appears to have, through a process of modification, achieved very satisfactory results. The OP is happy. QED.

On point 3. I agree jet size/ needle profile have nothing to do with cold start up, while using the choke. But they DO when the car starts cold with NO choke and floods. This was the OP's main problem ( among others), which is why quite a few posters focussed on it being a needle/jet issue. With the benefit of hindsight, we now know that this was the correct diagnosis.

Absolutely correct on all points thank you S-type.

[OrigCooperS]

Can I ask why many of you need a peg to hold the choke in the correct position? I’ve owned a multitude of Minis over the years and never once did I need a peg to hold the choke out, the ‘pull and twist method’ always seemed to lock the choke cable for me?

[MiNiKiN]

Can I ask why many of you need a peg to hold the choke in the correct position? I’ve owned a multitude of Minis over the years and never once did I need a peg to hold the choke out, the ‘pull and twist method’ always seemed to lock the choke cable for me?

This method, as intended by the engineer designing this semi-clever mechanism, works until the thing is worn - from then on you need a peg.

[Peter Laidler]

The later twist-and-lock choke cable retention method is indeed a clever design Minikin and OrigCooper. The wear usually starts to take place during the first few months from new and works reasonably well until the car is 13 months old - JUST out of the warranty period when it fails totally. Hence the peg.

As happened with mine. As I recall, JUST out of warranty or guarantee period it was quite an expensive repair because the heater had to be lowered and the switch plate had to be removed from the rear etc etc before a new cable assembly could be re-assembled. Then all the stuff and bits and pieces....... Anyway, you get my drift.