Hi, I'm looking for assistance, I have a mk1 Cooper S, I have fitted twin HS2' SU's after rebuilding them with new kit. I can't get it to idle below 2000 rpm with the idle screws backed off. I have only done static timing as per the manual. Needles are M and I have carefully centred them so they fall with a nice clunk.as far as I can tell the throttle discs are centred.Fast idle clearance is as per manual, both carbs measure the same airflow using the snail type meter. Vacuum gauge shows it's just above idle. When I rev it it sounds normal. plugs show its rich but the jet is as lean as I can get it after winding up from the base adjustment of 12 flats down It starts first try everytime with no choke.
Any suggestions are appreciated.
Thanks Stewart

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Mk 1 Cooper S 1965
If you could erase all your mistakes of the past
You would also erase the wisdom of your present
Remember the lesson not the disappointment.

Have you got a pcv fitted? Is the diaphragm ok? Does the RPM rise if you remove the oil cap?

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Thanks for your reply. Yes I do have the pcv fitted and it's got a new diaphragm. Removing the pcv and blocking the manifold off makes no difference. Removing the oil caps makes no difference, if I use them to push the dashpot down the idle does fall but won't stall.

_________________
Mk 1 Cooper S 1965
If you could erase all your mistakes of the past
You would also erase the wisdom of your present
Remember the lesson not the disappointment.

Hi StewartP
Had the same problem on my 70S. Couldn't workout why it was idling fast after trying everything I could think of to slow down the idling. One carby was the culprit. I took it to local mini mechanic who found one of the butterfly valve shafts was sticking. Might be worth loosening the valves and resetting.

Bazzz

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Mini Cooper S Mk 2, 1970,
Mini van 1970 with side windows now converted to 4 seater traveller

Stewartp
I think that Timmy201 means the engine oil filler cap. I remember reading somewhere that it has air holes that partly control the vacuum within the block and hence the action of the PCV valve.
Replacing the engine oil filler cap is mentioned in some service schedules.
Good Luck Dave D. (There are not many 65 S's around.)

Thanks for the suggestion I removed the dashpots and looked in with a mirror and light both discs are closed without the engine running.

_________________
Mk 1 Cooper S 1965
If you could erase all your mistakes of the past
You would also erase the wisdom of your present
Remember the lesson not the disappointment.

Thanks, By coincidence I tried that this morning their was a very slight change. I have a new cap on the way anyway as the minispares UK website says they should be changed every 12000 miles I have no history of mileage on all three caps i have.
Stewart

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Mk 1 Cooper S 1965
If you could erase all your mistakes of the past
You would also erase the wisdom of your present
Remember the lesson not the disappointment.

Is the cap you have now and the one on order a vented type?

https://minisport.com.au/products/mini- ... 8021&_ss=r

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Check seal between carb to manifold / manifold to head - could be a vacuum leak: Too much air will lean out the mixture and cause high idle.

With the rebuild did you replace throttle shafts / re-sleeve bore of the body? Although shaft spindle is brass, the bore of the cast SU body can also wear, and can be re-sleeved. Check leaks in this area spray a combustible liquid in the around throttle shaft and note any idle change

Yes the old one, and the one on order are vented, I believe I need vented for use with the pcv valve
Stewart

_________________
Mk 1 Cooper S 1965
If you could erase all your mistakes of the past
You would also erase the wisdom of your present
Remember the lesson not the disappointment.

Hi, I replaced the throttle shafts but decided I had no need to re sleeve the Bores as their is no play, if anything they were tight rather than loose,. I don't have the throttle cable connected so can manually push the throttle closed.I did have air leaks as the revs constantly rose to over 3000 then fell and kept repeating. It was a delaminating manifold gasket, since replaced with a new one. I have sprayed carb and throttle body cleaner with no change to idle.
Thanks stewart

_________________
Mk 1 Cooper S 1965
If you could erase all your mistakes of the past
You would also erase the wisdom of your present
Remember the lesson not the disappointment.

Revving like that can only be due to too much air getting into the engine, right?

Get a piece of rubber tube, hold it to your ear and down the throat of each carb, right up against the piston - is one louder than the other? If it is, then that carb is sucking more air than the other - the butterfly is open when it shouldn't be..

If they're the same, then air is getting in downstream, probably manifold...

Its unlikely to be the rocker cover cap or PCV, rule it out by removing the PCV from the manifold and plug the hole, still revving?

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did I tell you that I won a trophy?

Thanks for your suggestions. I have very bad hearing, Nil in left ear age related. I checked airflow with a snail shaped meter and both were the same. Looking in with a mirror both pistons have lifted about the same.
I have removed PCV valve and plugged the hole,
The carbs are Cooper not S so the driver's side one has the vacuum outlet for the Cooper Distributer. I had that blocked with a silicon cover, there was an extra hole in the manifold that had a set screw in it. The thread was bad so I drilled and tapped for a barbed adapter for the vacuum gauge. The pipe to the gauge is too small for that adapter so I blocked that and tried the gauge on the distributor take off. the gauge isn't showing any vacuum at that point. I'm not sure if its blocked or just not sufficient for the gauge. I'm about to try another set of carbs and different manifold. The problem will be this manifold doesn't have the takeoff point for the booster. BTW the booster isn't connected and the outlet is closed off.
Thanks Stewart

_________________
Mk 1 Cooper S 1965
If you could erase all your mistakes of the past
You would also erase the wisdom of your present
Remember the lesson not the disappointment.

I've used pcv valves with both types of rocker cover caps, they both ran fine.

Edited for clarity

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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.

Is there a blocked off Vacuum port on the inlet manifold? If there is try spraying Start Ya Bastard around it to if the revs rise.