First breakdown

[Alexlib]

1966 G3 with 500 conversion.
Went for a ride yesterday, after 60 miles at A road speeds going up hill on a duel carriageway the bike wouldn’t take more than three quarters throttle, shortly afterwards on a back road the bike started to misfire then stopped. Having no tools on me I waited for RAC.
The RAC man confirmed spark and cleaned the plug, the bike then started and seemed to run okay taking it easy.
No wanting to stop the engine I left it on tickover for a number of minutes .
Oil began to pump from the breather pipe near the alternator. Is this normal, it stopped when I started riding again.
The misfire and cut out returned later that day , I cleaned the carburettor jets and the bike seemed better, I suspect water in the petrol.
Grateful for any advice

[dave16mct]

Difficult to diagnose from afar but if you suspect the fuel put fresh fuel in and try that. Only try one thing at a time. Next I would try a new condensor or a good old Lucas one, often the cause of a misfire. (Are the points slightly burnt looking? Clean ad reset them.) Next I would try a new plug. Next I would check the tappets, should spin freely on TDC. Good luck.
Dave

[Alexlib]

Thank you , I will try that , the oil leak on tickover, is this normal? Does the scavenge rate on tickover lead to a build up of oil in the sump?

[dave16mct]

No it shouldn't be pumped out, just a few drips after stopping especially if on the propstand. Is there any blue smoke from the exhaust? Is the oil returning to the oiltank OK? Just thought , if the plug is getting very oily it could be causing your misfire.
Dave.

[Alexlib]

Thanks Dave
It only pumps out after tickover for 3-5 mins , if I rev the motor the oil stops.
The oil return seems to be as it should be from reading other threads.
No smoke from the exhaust, the plug is fouling but no sign of oil build up, I believe the engine is running rich and I am slowly improving the carb jetting .
But given me something to think about

[Alexlib]

Went on a 40 mile ride today with no problems

Seems the breakdown was caused by water in the fuel causing the bike to get very hot running lean

[clive]

Nice bike but I do wonder about the colour of the exhaust pipe. Has the bike been run with the ignition retarded.? The exhaust pipe has obvisly been overheated to go that colour and that's usually caused by an ignition setting that's retarded. If it's happened once the colour will not go hence I have a hint of it on my G11CS not the one with the broken crank, the other one!

[Alexlib]

Thanks Clive
It got very hot when it broke down, seems to be running well now although as I am new to matchless I could be wrong, hopefully will meet up with some other owners soon