I have a Colourtune and I've just been reading one of the faults in Test 2 where you slowly increase the revs.

For yellow flame between 1000 and 1700 it says..

"worn metering needle, inspect for scuff-marks at thickest end of taper.
Typical symptoms - idle mixture correct with jet screwed in further than usual (Normal posn. 2-3 turns out from flash with casting) accompanied by engine instability at 50-60 mph and during acceleration."

Maybe the needles are not only unsuitable they are also worn?

I don't remember a yellow flame, I'll have to take another look with the colourtune.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

fuel level in float bowl and check the position of the needle in the piston. Also check that the pistons are lifting correctly. If they are not then lowering the jet[choke] is allowing more fuel in to compensate for the piston not lifting.

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

From the specs given I'd say you need richer needles CP4 or No.7 would be a good start, very similar spec needles, No.7 from memory is slightly richer by a thou or 2 all the way down. (may even require as rich as MME's)

As others have mentioned here do the basics first . . .
1. check fuel delivery
2. check float bowls are clean of grit etc at bottom
3. check needles are the same
4. check jets are in roughly the same position
5. correct fluid and fluid level in dash pots (use ATF dextron3 is found to be best)
6. before adjusting any mixtures get engine to a good/normal operationg temp
7. without load (being driven) does the engine "breakdown" (cough and splutter)
8. if so spray WD40/RP7/etc onto throttle shaft ethier side of each carb to find out if it clears up or if you notice a difference in engine sound there is probably an air leak due to a worn throttle shaft and or housing which will probably require either new shafts and or bushes fitted to the housings.
9. have you checked the tension of the carbs onto the manifold or for air leaks . . . use wd40 etc to check for air leaks in that area aswell
10. check for air leaks around the inlet manifold/cylinder head face, check tension of nuts on studs . . . i hope you have the brass nuts on the studs as required.
11. it could also be the coil or a lead/s breaking down but check all the ignition coponents eg plugs, points condition and gap, cap, rotor, high tension lead resistance etc, etc . . .

Hope this info is of assistance

Cheers Scott

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http://www.youtube.com/watch?v=nDMkVq1jRGU

Thanks all for the responses,

I entered most of the suggested needles into http://www.mintylamb.co.uk/suneedle/ and they are all very similar with the exception of the ones I have fitted (M) which are the odd ones out showing up as quite lean so hopefully that is the problem. (see pic below, my needle is the red one)

I've ordered some #6's and see how they go.

..however I will check all the other stuff that people have suggested just to be sure.

Cheers

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

bleugh!! what a rubbish interface!

try mine - it ain't pretty, but you can search for richer or leaner needles based on what you've got, instead of guessing the letters.

http://www.morrismini.com/SUNeedlesV2.aspx?linklist=6;7;CP4;GT;M;MME;

I added 'GT' to your list, that's what I think I'm going to try next, leaner at cruise, richer at bigger throttle openings

Ok I have taken the Carbs off the car and there is a little bit of play in the spindles.

Can anyone recommend someone to check over the carbs and overhaul them as necessary.

I was thinking of Midel but if anyone has further recommendations let me know.

Cheers

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

i find it difficult to believe that """slightly""" worn shafts would interfere with or produce any (much) drama with engine revs up where you`re talking about,,, with throttle open some-what, the shafts wear plays less havok than on idle or very slight throttle

but still if you want them "Perfect" then by all means don`t let me stop you spending time & money on them,,, i like them all nice & lovely before i tune them too

you live up north-ish somewhere don`t you Phil ??? The guys at Carb-Tech in Kipparing are legend carb repair people , Ian Stewart (Navigator for one of the fastest Aussie rally drivers) works there & is VERY VERY good carb specialist, i would suggest he is one of the Very best in the Brisbane area.

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Yes I realise probably not related to my original problem but while off the car thought i might get them checked out.

I had been having a little trouble with the idle, namely it would be high and then slow down, but with the needles I had I think I was having to have a really rich idle to get correct mixture at speed.

I guess I might only need new spindles, the body might not need rebushing.

I'm in Wollongong actually but work in Sydney.

I did discover a manifold nut was loose/damaged so replaced it and it's nice and tight now, that may have been part of the original problem.

The needles I'm sure were not suited, I did a bit of experimenting and as I increased the mixture the problem moved further up the rev range.

I have some new needles now which should be richer at higher revs.

Trying to check my floats now (see new post)

Have checked fuel flow rate. It pumped 140mls in 15 secs so 560ml/minute. Someone said should be 1 litre per minute so maybe this is another issue?

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)