Okay, I’ve been playing in the garage. I realised that after rebuilding the carburettor I had left the pilot jet (air screw) full in. The bike would start but only run for two seconds before stopping despite encouragement from the throttle. So I started to think that my problem was due to the air/fuel mixture being to rich. Easily solved I thought.
After attempting to start the bike with the pilot jet (air screw) at varying positions from fully out to fully in and seeing no affect I realised that it was not going to be that simple. Any way the pilot jet only comes into effect when the throttle is fully closed because it is part of the idle circuit and I usually open the throttle about one eighth open when attempting to start.
I then had a look at the spark plug. It was dry and black; a light rub showed a nice grey brown colour. The spark plug is a new KLG super M30 so I changed it back to the old KLG M30, but this had not noticeable effect.
I did have one miner success. The fuel was some times coming out of the top of float chamber. It is a bottom feed float chamber. I looked inside the float chamber which is new and realised that the float needle had two notches so I placed the needle retaining clip on the lower notch, which means the fuel level will be lower in the float chamber. This stopped fuel coming out of the top periodically but did nothing for starting the bike.
The bike has been on the road running since I cleaned the tank out, replaced the petrol tap and rebuilt the carburettor, however at the moment it seems to only fire for two seconds then die. After this it will not fire at all unless I leave it for about 1 minute with the fuel tap off. What is this telling me?
AMAL 276 PRE-MONOBLOC CARBURETTERS
Do you need one thousand words or just one picture?