Try tweaking the clutch adjustment first, heck of a lot easier than messing about with the engine.
I'll give that a go, but the clutch does disengage and engage properly, bites around 1/2-2/3 of the way out on the lever. the arm is sitting around 20 degrees below horizontal, so I think it's probably worn plates.
When you say you messed up a couple of shifts,,did you by any chance over-rev the engine?
The loss of power in 5th gear is a bit worrying. Does the oil light ever come on?
yes, I did rev the engine quite high in 4th before going into 5th, but not past the redline, only to about 8-8.5 and it was accelerating nicely all the way up 80mph, when I changed into 5th initially it was ok, but after going for a mile it started to lose power. yes, worrying indeed. but no the oil light never came on.
A few miles later, riding along in 5th at 70, I started to lose a lot of power, almost like my clutch was completely slipping
you should have been revving at about 6 thou at 70
do you mean it was revving high but going slow/er?
these old bikes all clank a wee bit but
summats obviously wrong, what have you been doing to the bike?
any major work/been fiddling about in the guts recently?
yes, I was doing about 6k, when it started to lose power I was still at 6-7k, but the speed fell off to about 45mph, revving higher didn't do anything really. I think it may have dropped to lower revs a while after that but I was kind of worried as there was no hard shoulder and it was a speed limit road (A4 to bath, just before Keynsham)
Engine was out because I had a small spill and cracked a rocker cover, got a few stones in the engine, but luckily it stalled before any damage was done. full strip down and inspection revealed no damage to the bores/bearings or anything else really. I put everything back painstakingly using all the manuals and many photo's and I'm 99.9% sure I put it together right and torqued up accurately. it's done over 100 miles since the rebuild and mostly it's been running very nicely indeed, the gearbox was even smoother than before.
who knows then... I might replace the input/output shaft bearings with new ones because they were not 100% and inspect all the worn parts and swap those out.
just gutted because my garage is miles away in the country and I'll need to walk/bus back after dropping the bike off. need to invest in a trailer for my car.