Righto, after blowing the head gasket last weekend (and replacing it last night), I'm finally getting around to tuning the Moke.
It's been running like quite a dog since I bought it , but I have been too lazy to do anything about it.

Dwell has been set at 55 degrees.
Static advance at 8 degrees.
Tappets are at 12 thou.
All that is set as it should be.

The only thing that isn't right is the fuel mixture.
It currently has a DL needle in it.

A bit about the engine now...
Standard 1098. Completely standard.
Standard exhaust, on factory cast manifold. Everything is stock!

I am thinking the DL needle is not right. Beanie has had a play with the fuel mixture. It idles alright, but then upon driving it, it has a massive flat spot at (without a tachometer) i'd say around 3000rpm with any form of load. Its not just a flat spot, it breaks down and sounds like its missing.
Lifting the dashpot through the back of the carby, the engine revs pick up slightly then come back to the same idle...

Any input would be great.

Nothing a monster tacho wouldn't fix.

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One should never skimp on the zip ties.

Floating or fixed ?

Floating - ADC

Fixed - HG ( Standard needle 1071 Cooper S )

Both of them are better than the standard AN

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possibly try a "RED" spring & an "OA6" needle for starters ,,, see how that goes,,, then come back here & tell us all how that went & we can go from there yeah?

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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.

Forgot a couple of pretty important things didn't I

SU is HS4 (1.5").
Needle is fixed.

Not sure what colour the spring is.

oops,,, my bad,,, sorry i didnt read your post very well at all,,, DL needle hey? Hhmmmm;;; ok try RED spring & CP4 or an MME & see what happens then ok?

edit,--->,, those needles & spring combo may be a tad rich for you but at least it should get rid of the (by the feel of it) lean flat spot (as long as your piston & bell assy is free & smooth & not catching on any sh!tty patch inside (make sure it`s all clean in there) But at least we can go from that point with a new "Feeling" (over the net it`s pretty difficult to tune someones engine for them so all i can describe it as is a "Feeling" & maybe get it closer

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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.

Sweet, I will give that a crack when I can next get my hands on some spare needles.

willy, I have a spare CP4 you can try if you want. If no worky, just post back.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

CP4 or if you need a slightly richer needle a No.7 ........ what fluid are you using in the dashpot?

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

Scott, we went from nothing at all (eep!) to using ATF.
Helped a lot with going from idle to wide open throttle quickly - relieved the spike in richness.

Actually I think you'll find using oil vs no oil will allow the carb to produce a richer mixture under acceleration, not reduce the richness.

Allowing the carb piston to rise quickly (i.e. no dashpot oil) admits more air into the engine, reducing velocity over the bridge (therefore picking up less fuel) which leans the mixture out. Using a thicker oil (or going from none to ATF) slows the piston's rise, which causes higher air velocity over the bridge, drawing out more fuel per cc of air.

As described earlier, it sounds like you may have had a leaning out problem at higher revs, which would have been exascerbated with no oil in the dashpot. Using a really thick oil would compensate for the too-lean needle a little, but throttle response will suffer as a result.

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Simon

The adventures of an owner builder in the Tallarook Ranges

Sorry, my bad, yes a spike in leaning out.

Does anyone know what characteristics the DL needle has?
Or what application it would be used in.

I just thought I'd ask as I have seen many types and mixes of fluid in dashpots in the workshop and was wondering if you may have been using either a fluid that was to thick or to thin.........
ATF is what I have been using after speaking to a person who has been playing with SU's since god was his next door neighbour when they were just young kids.

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

compare the needles here willy

http://www.morrismini.com/SUNeedlesV2.a ... P4;DL;MME;

obviously your DL is riduculously lean compared to the others, the CP4 looks good because it is slightly leaner at idle and cruise, but obviously opens up... starting with one that is a bit leaner at idle means you can richen it up across the whole range if you need to, but starting with one that is rich at idle means if you want to go richer at the top end you've gotta get another one, or file it

(must write a help page for that one day...)

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did I tell you that I won a trophy?

Fantastic site Simon, similar to one Dr Mini showed me.

Well that graph certainly makes clear about the tuning problems I've been having!

CP4 should be on the money.
Beanie has a 7 in an SU he has spare. Could try that, but by the looks the CP4 is very very close in profile to it.

Doc is sending a CP4 over for me to try.
Fingers crossed it will work smoothly

& i will give the carby slide & body a good cleanout when I change the needle and let you know if it feels gritty or anything before. I am pretty sure it flowed quite nicely down the slide of the dashpot.