marshg246
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- Joined
- Jul 12, 2015
- Messages
- 4,762
Some time back bought a partly built Combat. It was being put together with a monster single carb, a Harley oil tank, extended forks and supposedly a professionally rebuilt engine. I have a customer who wants a stock Combat. So, I started on it. If interested, the writeup of the build is here: https://www.gregmarsh.com/MC/Norton/CustomerCombatBuild.aspx
The engine cases were not cleaned up when it was built so apart it came - found plenty of problems so it was good that I took it apart.
Everything was going OK but on the first quick test ride, I noticed a little oil smoke from the left exhaust. It didn't clear up so I figured that the valve seal had split or come off. The bike ran very strong and was more of a bear to kick than the last Combat I built but I figured that was the new +.020 over pistons, new valves, new cam and so on. So, using the rope trick, I removed the springs from the left-side intake. The seal was fine. So, something I truly hate and have trouble doing by myself on a Norton had to happen - off with the head.
If quickly became apparent that the new copper head gasket was bad. I should have inspected it before installing but I didn't. I didn't have another in stock so I reassembled with fire-ring composite gasket. Started the bike and there was a noise that wasn't there before - WTF! So, off with the head again. My stepson was helping me and thought he heard something fall out of the head. So, another new head gasket and back on. Now the noise was louder!
Today, I took the head off again and can see where the left exhaust valve is just touching the piston! I compared the head to another Combat head and it has clearly been decked! I should have caught it before when I noticed that the rocker adjusters barely stick out of the rockers! I haven't done any precision measuring but it looks like .020-.030 has been taken off the head. It is flush with the bottom fin.
It's a real shame since the head has new guides, black diamond valves, and new springs. I hope the spare head I have is has good guides and seats - it has no valves.
The engine cases were not cleaned up when it was built so apart it came - found plenty of problems so it was good that I took it apart.
Everything was going OK but on the first quick test ride, I noticed a little oil smoke from the left exhaust. It didn't clear up so I figured that the valve seal had split or come off. The bike ran very strong and was more of a bear to kick than the last Combat I built but I figured that was the new +.020 over pistons, new valves, new cam and so on. So, using the rope trick, I removed the springs from the left-side intake. The seal was fine. So, something I truly hate and have trouble doing by myself on a Norton had to happen - off with the head.
If quickly became apparent that the new copper head gasket was bad. I should have inspected it before installing but I didn't. I didn't have another in stock so I reassembled with fire-ring composite gasket. Started the bike and there was a noise that wasn't there before - WTF! So, off with the head again. My stepson was helping me and thought he heard something fall out of the head. So, another new head gasket and back on. Now the noise was louder!
Today, I took the head off again and can see where the left exhaust valve is just touching the piston! I compared the head to another Combat head and it has clearly been decked! I should have caught it before when I noticed that the rocker adjusters barely stick out of the rockers! I haven't done any precision measuring but it looks like .020-.030 has been taken off the head. It is flush with the bottom fin.
It's a real shame since the head has new guides, black diamond valves, and new springs. I hope the spare head I have is has good guides and seats - it has no valves.