Mystery non-start issue. Help needed!

[svenedin]

Definitely confirmed fuel pump running fine as directed the input to carb into half a Coke bottle which it filled at a good rate. Fuel looks a little yellow but certainly seems petrol-like.

Having taken air filter off, carb piston does seem to have a bit of a buildup of black gunk on the side, I've run out of time today to take any more photos but will have a look tomorrow when I get a chance and snap some more pictures, as well as try and get the float bowl off to check for crud. The carb piston does seem to move up and down, albeit a small distance.

Will also snap some pics of the distributor side to check I've not been an idiot again. As far as I could tell earlier, when no.1 piston was at TDC, the rotor wasn't exactly on top of where one of the distributor lobes should be, but just before one (which I assumed was 1 and then set the rest up following on)

I do appreciate all the help here, I'm doing what I can but admit the limits of my own spannering quite freely.

Updates to follow

The trouble is fuel goes off and it really doesn't take very long. The petrol shouldn't look yellow. It suggests the fuel has gone bad. If you have an original fuel tank then there is a drain plug at the bottom of the tank. It is a nuisance to have to do this as it is potentially dangerous to drain fuel and you will then have to dispose of it appropriately. Alternatively, you can direct the fuel hose from the pump into a Jerry can and run it until the tank is empty. I'd try the Easy Start idea (https://www.halfords.com/motoring/engin ... 93737.html). Incidentally, carburettor cleaner will also start an engine if squirted in having removed the air filter. If the engine starts then you are narrowing down the problem. If you are going to take the lid off the float bowl make sure you have new gaskets on hand as it is almost guaranteed that a gasket will tear and then leak if you have no spare!

Stephen

[tjcmus]

Hi all,

Apols for delay - life has got in the way, as it tends to. Had a chance to get the carb mostly apart this afternoon to check if it was gummed solid, and although the fuel does seem a bit yellow, there's no sediment in the float bowl, the float moves fine and actuates the needle, which itself moves fine.

The dashpot had plenty of oil, and although the piston had a bit of a black residue on it, it seems to move fine, and the choke mechanism seems to work fine at the bottom of the carb. I stopped clear of taking the carb off the engine, as I have no gaskets, and it does appear to have been sealed in with something or other - it ain't budging.

I will reassemble the carb and try the Easy Start/carb cleaner idea, which if it works would be just typical, but at least sort the prob.

I have a niggling suspicion that there's something off with the ignition/points/condenser though so may just order a service kit to be on the safe side, but if that doesn't suss it I really am out of ideas.

Photos attached of partially disassembled carb etc - you can see the black gunk around the top of the cylinder.

IMG_20241110_153217.jpg (1.33 MiB) Viewed 743 times

Will report back on any progress. Thanks again.