There are lots of things which can make a mini run that bit hotter than normal, however give the car a bit of a health check first. Make sure oil and water, are topped up and healthy looking. Feel the top hose from the radiator to thermostat it should be hot once the car has warmed up.
Have another check of the exhaust manifold for leaks. If you smell fumes within the car also don't forget that a hole in the back box could let fumes in from underneath the car. So it may not be just the manifold.... Again worth a check. After a good run out somewhere, take a spark plug out and take a look at the colour especially on the tip or around the shroud. There are lots of guides on the internet regarding the correct and incorrect colours. Basically black is rich and white is lean. Ideally you want to find a peanut to light brown colour. That way you are at least in the ok'ish ball park. Remember 1 carb feeds engine cylinders 1 & 2...the other feeds 3 & 4. So for good measure check all 4 spark plugs.
Before making any adjustments, check your carb damper for oil. Official recommendation is an SAE20 grade oil. However, in truth most use their regular engine oil to top it up. It only needs about 4 ml. You'll feel some resistance and hear a slurping noise as you push the damper back in. Try to give both carbs the same level of oil.
Generally minis can run hot from the mixture being too weak or drawing additional air into the intake. Again get the car warmed up and then use the piston lifting pin, underneath at the side of each carb. Push and hold the pin up. The cars RPM should increase temporarily and then return the approx the same rpm. If it increases and stays increased...its too rich. If it increases and then almost dies...its too weak.
Assuming you are using twin hs2 or hs4 SU carbs. Firstly check that the choke linkages and mechanism for each car is not sticking or catching somehow. Rotating the mixture nut beneath the SU carb is how the mixture is made richer or weaker. Anti-clockwise for weakening...clockwise to richen. Its a hex nut,so only adjust 1 flat of rotation at a time (Ie 1/6th of a full turn of the hex nut), before re-testing. Don't forget to give the throttle a quick blip in between tests. Again lots of guides on youtube etc. If you do try it and the mixture gets screwed up. Simply reset everything by fully adjusting anticlockwise until it cannot go any further and then adjust 10 to 12 flats clockwise. You'll be back in the ok'ish ballpark again.
Balancing the carbs is really easy, and made a whole lot easier using a good carb balancer (not the gunson balancer - its rubbish!) or even a simply length of tubing to listen to the air intake of each carb. Slacken the throttle linkages. Then adjust the idle/tickover screw on both carbs until they are drafting the same amount of air...or making the same intensity of hissing when listening through the tube (Listen from the same reference point of each carb Just behind the piston). Then adjust each carbs idle screw up or down until they both sound the same reading or hissing intensity, and your tickover rpm is where you want it to be. Then tighten up your throttle linkages. A final check is to put a shaving mirror behind the carbs with the airfilter removed....and blip the throttle a bit to 2 or 3k rpm and use the mirror to watch the piston inside both carbs rising and falling at the same time as each other.
Your first move though is a general lubricant and water check and a look at the spark plugs!!
Good luck.
Edited by stevegrabba, 23 October 2017 - 06:12 PM.
