My trusty Rap was running fine today when I stripped the heads off to replace leaky upper seals on a couple of the pushrod tubes. (Those little blighters don't seem to last long do they?).
When I removed the front head, the piston showed some interesting markings adjacent to the carb showing a clear strip of piston like it had been washed clean by petrol. The front head shows a similar phenomenon in the same place. See pics - which I hope I have attached properly. The outside of the inlet valve is also oily - so it could be the valve-guide seal is on its way out too?
I'd be interested to receive opinions as to what is happening here.... In the meantime, I'll carefully strip the head down and photograph it as I go.
Peter B
Bristol, UK.
PS The rear head combustion chamber is dry with a mixture of dark grey and brown deposits - light brown on the head of the exhaust valve. Oh, and if anyone is interested, the pistons are Suzuki; they must have been in for over 15 years now, eh Trev? There is no wear and no scores in the bore (despite no air filters), I can still see clearly the 30 degree criss-cross honing marks in the cylinder!
When I removed the front head, the piston showed some interesting markings adjacent to the carb showing a clear strip of piston like it had been washed clean by petrol. The front head shows a similar phenomenon in the same place. See pics - which I hope I have attached properly. The outside of the inlet valve is also oily - so it could be the valve-guide seal is on its way out too?
I'd be interested to receive opinions as to what is happening here.... In the meantime, I'll carefully strip the head down and photograph it as I go.
Peter B
Bristol, UK.
PS The rear head combustion chamber is dry with a mixture of dark grey and brown deposits - light brown on the head of the exhaust valve. Oh, and if anyone is interested, the pistons are Suzuki; they must have been in for over 15 years now, eh Trev? There is no wear and no scores in the bore (despite no air filters), I can still see clearly the 30 degree criss-cross honing marks in the cylinder!