At this point it looks better in the pictures than it actually is. Once I got it onto my stand I gave it a cursory examination, I think it must be out of an 750SS as it has the mechanical rev counter drive on top of the horizontal cylinder head. The ignition pick up leads have definitely seen better days, worryingly the gearbox sprocket has about 6mm slop radially around the centre line of the output shaft but only about 2 - 3 degrees circumferential slop, so hopefully it is the sprocket splines that are worn and not the shaft
Today I attacked it with the dead petrol drained out of the ZX9R. Whilst petrol loosens the grease and grime it is not very good at actually de-greasing as it evaporates as it runs off and merely spreads the crud more widely. It was all I had to hand and I thought I ought to get some value out of stale E10 petrol.
The engine original colour was I believe silver but it had been brush painted with another silver that barely survived the petrol wash. The barrels and head had been also brush painted with black using a bog brush by the look of it.
After about an hour I was able to examine what I had more closely without being afflicted with congealed chain grease.
The good news was that the swinging arm bearings had been removed from the back of the crankcase as they can be an absolute swine to get out. The bad news was that I found this.
The hole in the drive side crankcase for the swinging arm is at least 1mm oval measured 3 o'clock to 9 o'clock compared 12 o'clock to 6 o'clock. The right hand side measured with a digital caliper is still round. I do not think anyone extracted the drive side swinging arm needle roller bearing I think it probably fell out.
Many would at this point simply break the engine for parts but somehow I do not want to do that and anyway I love a challenge. I think what I will need to do is make a jig so I can bore the drive side case out and fit an oversize bearing, the difficulty will be in ensuring that the hole is at right angles to the split in the crankcases and parallel to the rear wheel spindle. I do not have a milling machine and only a small lathe, it will certainly exercise the little grey cells (both of them).