I've been trying to figure out why the Mini (1989 998cc stage 1 kit fitted with a HS4 carburettor) has been running hot, primarily at higher speeds such as on the motorway. I've checked the temperature gauge which looks like it goes up to about 90-95 degrees. I've upgraded the radiator to an aluminium Fletcher rad in hope that it may help the issue, which has helped a bit, but not enough that it still runs quite hot at times. However, when sitting it traffic, idling the temperature sits bang on where it should be in the middle.
After looking at the past MOT emissions test, the CO reading is 0.56% and the limit is 3.5%. I've heard many stories of fellow Mini owners having to weaken their mixtures to pass the MOT check, is this a hint that the Mini may be running too lean, causing the overheating?
One other thing which may also be a hint that it's running to lean (or something else entirely!), which is whilst cruising and then applying full throttle it'll feel as if it holds back, then after around half a second it'll then accelerate as it should.
If anyone can shed some light on this it will be much appreciated! Many thanks