With over 85,000 miles under the wheels and a propensity for this to happen on the 450, I suspect my luck ran out.
The design was originaly for a 175cc and the 450 puts out a fair bit more torque than they do. It is most common in race machines using 450 clutch springs.
Replacement parts are available for some items, some new, some secondhand. But, things like the clutch spring cups are unobtainium and a bu**er to get made. They are normally pressed from mild steel, but nobody has the tooling and it's expensive to tool up, whilst the Manx Norton ones (don't fit!) and in stainless (so that they don't rust and an "eyesore" on the exposed clutch) are now £10.50 each + VAT +P&P and I need 6 of them!
I have looked for alternatives, including speedway ones, but so far nothing has appeared.
I have managed to source a new cover, inspection plate, springs, retaining screws etc and now have to modify the clutch hub to a race spec., with homemade pillars and a different fixing method. The problem is the reduction in size of the pillars to 5mm from 8mm as they pass through the drum and are rivetted over at the back. the pillars snap at the edge of the reduction in diameter. On mine you can see that it appears that the factory nicked the pillar and then moved on a bit before cutting to length, hence the weakness. Some people put a TIG weld on them, but that can create cracking in the hub due to heat stresses in the material.
A new full spec race clutch hub is a work of art, but at £360 + VAT + P&P a bit steep!
So, the SRX Mono will put some more miles under the wheels and the spanners will be twiddled some more. As SteveL and I would say "Yew keep a troshin bor!".
Good health, Bill