Honda-SOHC

For the second time since the bike's rebuild the circlip parted company with the shaft today.
Just made it down a slip road in second luckily.
I may have used a non standard circlip burpt it looks like the groove in the shaft is a bit shallow?
Anyone here come up with a better way to retain the lever in this setup?

Many months (years?) of head scratching over my poor running but totally re-built motor may nearly be over ?
Lack of any real pull and bogs down under load.....just about gets to its MoT test.
Re-tracing events prior to this....
The head gasket got replaced again after removing the cover to retorque when some stripped threads in the head meant it had to come off for repair with inserts.
The second gasket was also genuine Honda and the retorque was done after an initial running.
Eveything else has been checked and re-checked over and over.....ignition, carbs balance and float height fine, tappets set, camchain tension ok... Nothing left to do.....but hard to start the thing  !
Once it is going and warmed up it idles quite steadily but revs up a bit like like a twin.... Kind of harsh and the exhaust note isn't right. Plug colour is ok though. No smoke either.
Did a cold compression check with carbs on and off with the same results....170 150 150 170 psi both times. Then did the check after warming up......150 150 150 150.
Counter intuitive I thought....compression worse when hot  on cyls 1 and 4 ??
I can only think the gasket is leaking between each pair of cylinders where the clamping pressure is weakest/ gasket narrowest?
When cold it seems that cylinders 2 and 3 under compression lose pressure to the outer cylinders which are on their inlet stroke....2 and 3 fire with 1, 4 compressing so no loss of pressure?
Is this right?... Assuming 1,3,4,2 firing order is right.
 
Maybe re torquing again will work, maybe not?
Probably a new gasket, seals.....££

Does anyone have one of these (in a box,shed, loft) please?

Preferably not dented or holed...
So one that's fit for re-plating.

Thanks

My 400/4 had an aftermarket BSM exhaust when I got it back in 2006.
I have got the bike back to standard spec including the exhaust system (once those downpipes are sorted).
The BSM pipe has been hanging around in my garage gathering dust ever since it was removed.
Funds are needed for other items so it's got to go.

It has buffed up very well and seems to be made from a grade of stainless steel as there is no sign of rust or pitting anywhere. Looks like it was designed for a long life and the welds are neater than Honda's OE.
If I intended to use my bike for commuting I would fit this pipe !

 There are a couple of minor dinks in the silencer which hardly show.
The BSM people are still making these in Holland and they list this system as a 'Classic' style for 400 Euros or so.

If anyone would like it, please make a sensible offer.