Hi folks, I have an intriguing problem with my 1967 S2a. It wont start with any amount of cranking, but as soon as you try starting fluid it fires up fine, then runs sweetly. Subsequent starting is then a bit hit and miss - and if it does start it requires quite a bit of cranking. Same performance with air filter on or off. Have replaced carb, in-line fuel filter, fuel lines (new), and tank and I've reconditioned the fuel pump. I am still suspicious of the latter though as when I blow into the outlet (or suck on the inlet) a bit of air still passes. I tried a secondhand pump and that didn't result in any improvement (the pump worked fine on another s2 I had a few years ago, but to be fair, also fails the suck/blow test). Might still be pump? Could it be too rich mixture? Doesn't obviously seem to be blowing dark smoke. Compressions on all cylinders are 140.