Hi guys, I've finally got around to the point where I can follow this up now.
Since my last post in August I've gone through quite a bit trying to get this running properly and although it is much better it isn't quite right yet.
From where I left off above:
1. I swapped the valve seals and checked the shim clearances. Clearances were well out but put it back together with the new seals to see if it improved but it didn't.
2. Stripped off the heads and swapped out all my shims as the tolerances were well out, found that one of the front valves was very slightly bent. It still sealed properly but can't have been healthy. Also found that the little oilway stud hadn't been seated properly previously and had dented itself into the barrel so it didn't locate all the way down. Fixed all this and it ran better but still heavily fouled the rear plug.
3. Removed the heads and barrels, found a shattered oil ring in the rear piston. This will account for all the metal around the sump plug. Gapped the new oil ring, put it back together and it ran even worse than before. It bellowed smoke out the back and spat oil out of the exhaust joints!! As it was worse than previous but now actually had an oil ring that lead me first to the oil seals I had swapped. Bought a new set and fitted them which sorted all of the smoke and oil coming out the back. Looks like I had nicked one of the seals slightly when fitting them and even a tiny bit of damage caused a LOT of oil to get through.
4. Ran a compression test, adjusted the mixture again and sync'd the carbs. All was looking much better but not quite right still. On the road the clutch was slipping badly and when you went through the rev's the bike still pop's between 4-6k rev's. At this point moving house and fitting a kitchen halted progress for a couple of months.
5. Fitted new clutch plates and oil seals a couple of weeks ago and the bike mostly pulls like a train all the way through to the top end. It isn't hesitant but it still pops slightly in the mid range. You notice when trying to hold a constant speed and as well as hearing it you feel it through the bike. Took it for a blast to my brothers and pulled the plugs out where I saw the back one fouled up again quite heavily with carbon and oil. As I couldn't remember when I swapped it out last I just bought a new set and rode it from Redditch to Blakeney (about 60 miles). Took a look at the plug again today and it doesn't have a heavy build up of crap any more but it has a light coating of oil over it still...
Now at this point I'm running out of ideas. It is much better than it was and it is rideable now but I don't like doing things by halves and want to nail this down but I've swapped out everything I can think of so any suggestions are appreciated!!
From here all I can think to do is swap out the rear valve stem seals one more time in case there was an issue from fitting them. But as it has had a new oil ring, new valve seals, new shims, new o-rings, several sets of new plugs and lots of TLC I was hoping it would be sorted by now.
