One of my 'gulls runs so hot that it misfires and almost seizes! It's a 1951 AD in good condition(bearings,water jacket,carburation etc) but after about 20-30 mins running it gets VERY HOT and the crankcase is so hot that I can hardly touch it This problem has only started recently. My other motors,SD,AC and WSC run COLD in comparison! It pumps plenty of water which is why I can't understand why it runs so hot. My 1944 SD can run ALL DAY and still not get that hot. Has anyone else had this problem?
Remember,dust and dirt are the enemies of all moving parts...keep your motor clean and it will repay you!
Water ways. Close to the spark plug there are deposits so the water can't reach where it should. There is still flow but hot spots occurs.
Fuel/carburation matter. Too much oil could lead in the crankcase being too hot. Or maybe the carb has a wrong jet or generally something wrong. That leads in wrong mixture etc.
Check those to things please (not judging from the water flow) and let us know.
Everything looks fine to me. Carb is correct,mixture correct. As for the crank,the flywheel came off same as the others and the motor starts easily and runs smooth until hot then the problems start! There is no vibration or strange noises,that's why I can't figure out what the problem is...
Remember,dust and dirt are the enemies of all moving parts...keep your motor clean and it will repay you!
I think David is right, it urgently needs a full strip down!
If the crankcase is running hotter than the cylinder base next to it, ignoring the insulating paper gasket between them & the fact that there is about 400 litres of cooling petrol/air mix passing through it every minute, there is a major source of heat creation where there should be none!
It shoud be very obvious on inspection, where the problem lies, if it will stop the motor.
Make it idiot proof and someone will make a better idiot.
Here's a look at the inside of the AD. There is no more wear than normal in big end or small end,I have certainly seen worse Seagulls and they didn't run hot! I have been rebuilding engines for years and I can't see any reason why this one runs hot and yes,the water passages in block ARE CLEAR!!!
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Remember,dust and dirt are the enemies of all moving parts...keep your motor clean and it will repay you!
You have had the head off then and seen that they are clear?
Sorry about that as you said it was a model 102 AD.
So when you say it's pumping enough water, are you going by the telltale where the cooling water enters the exhaust tube?
Is it possible that the only exit water is that coming out the telltale, with none exiting inside the exhaust tube?
Last edited by phil on Fri Jul 19, 2013 8:55 pm, edited 1 time in total.
Any coke deposits in the area near the little end? I had an occasion with a piston that had a small hole and let the combustion reach the little end, but this won't be the reason to get your engine run hot..
In addition, do I see a discoloration on the big end?
This problem has only started recently. My other motors,SD,AC and WSC run COLD in comparison! It pumps plenty of water which is why I can't understand why it runs so hot. My 1944 SD can run ALL DAY and still not get that hot. 
Has anyone else had this problem?
I have been rebuilding engines for years and I can't see any reason why this one runs hot 
and yes,the water passages in block ARE CLEAR!!!