So here is whats i have been up to.
I'm happy with the de-greasing results, but it would not take the tarnishing off the inside.
I took the block and crank to my nearest engineering shop for inspection and it turns out that the bottom end has had a rebuild at some point and just polished the crank and re-honed the cylinders. Although the bearings and piston rings looked good i will replace them whilst i have it stripped down.
Unfortunately, the engineers shop were not familiar with machining the block to fit a rubber oil seal.
So i decided to go with the rope seal. This is a bitch of a job, it took all day to press and crush the seal a bit at a time, then turn the crank, then remove and re-lubricate it and start again gradually increasing the pressure on the bolts and using a sash cramp to keep the end cap square as it would tilt using the bolts alone. There's no way you could ever do this with the crank in situ, its far too thick.
Next was the cylinder heads, i bought some later heads off eBay which were in pretty good shape. I made a jerry built jig so that i could press the old valve stems out and new ones in. with the aid of a 10 ton jack it worked surprisingly well.
New valve stems and oils seals in place.
New springs and valves fitted using the old spring caps and colletts. The valve and seats were re-seated the old way.
Bit of a jump as the pictures between these 2 didn't save for some reason. still it saves you getting bored.
At this point nearly everything is re-fitted, i upgraded the timing cover and oil pump with an one from a SD1 which is a straight swap and has the bonus of a rubber oil seal.
New cam shaft and bearings were also fitted.
Next it was the turn of the carbs, a complete strip down and new carb service kits from Mark Gray whether they needed it or not, who knows.
Now fully assembled, i decided to upgrade the air filters as the old air box had rusted through in places.
Work on the gear box is about to commence, i was hoping to replace the 4 speed box with a 5 speed SD1 box, but in over a year of watching they never seem to come up for sale in my area and looking at the price people are asking i'm not sure it warrants the money?