4 replies to this topic

[wesson124]

As said before, i need some base settings for the hs2 carbs on my 998 cooper engine - mk1 1965.

can anyone help me out?

cheers

[Sherlock]

Warm the engine to normal running temperature & switch off. Slacken the throttle connecting link clamps, unscrew throttle stop screws until they are just clear of the stops, (throttles totally closed) then set each screw 3/4 of a turn open. remove dashpots & pistons & screw jet adjusting nuts upwards until the end of the main jets are level with the bridge of the carburettor, or fully up if this can't be achieved & re-fit dashpots etc & top up dampers with oil. Turn down each adjusting nut by 2 turns. (12 flats). At this point the engine should start & by listening to the intakes with a tube you can balance the airflow by adjustment of the throttle stop screws. Re-secure throttle link clamps allowing about 20 thou clearance on each before they start to open the throttles. This must be exact on both carbs to ensure correct throttle response. Standard needles are GY. Weaker version: GG. Richer: M. When doing this, ensure that the throttle return springs on both carbs are in place.

[Ivor Badger]

Take the dashpots off and set the jets level with the top of the brass tubes. The turn them down 2 1/2 turns, 15 flats. That is near enough running setting to get the car running. Then warm it up and balance them out. Set the tickover with the throttle links disconnected, then set them so the butterflies open together.

by the way, the rich /lean needles don't work to adjust the mixture under normal conditions. The rich needles are for use in winter in cold conditions, ie Scandinavia and the lean for use at altitude.

Edited by Ivor Badger, 01 December 2009 - 12:44 AM.

[dklawson]

There is little to add to the posts above. What's most important is that you asked the question and did not assume you could just slap the carbs on and have them work.

I encourage you to print out the posts above, and sort of consolidate them. Then Google the topic for more information. There are LOTS of web pages out there discussing SU tuning. Read your Haynes manual AND if you have it, read the SU manual and/or the Haynes manual dedicated to Weber/SU/Stromberg carbs.

What was not mentioned above was that you must also loosen the choke linkage and make sure the choke's fast idle screw(s) are completely backed out/off before making mixture and idle speed adjustments. Again, that will be well documented on various web sites and in the SU and Haynes carb manuals.

If you visit YouTube you can search for videos by John Twist of University Motors. John closed his British car shop earlier this year after several decades. However, his maintenance videos are still on the web. I think his carb tuning videos are dedicated to HIF type, not HS, but the methods are similar and it wouldn't hurt to watch those. You will also find several videos on YouTube that cover the tuning of the Hitachi (SU clone) carbs used on Datsun/Nissan cars. They should also be informative.

[Sherlock]

The rich option needle is often required when using open air filters or ram pipes instead of the normal filters & airbox which draws warm air from the vicinity of the exhaust manifold. I only mentioned them as an element of the initial set up, as if all does not seem right, it's essential to know whether the needles fitted are the correct ones.