Well, I spent a long time yesterday sorting out and cleaning the various parts that came out of the destroyed engine; not everything is scrap, but I'm throwing away the cases, gearbox, crank- everything inside the engine except the clutch and cams, really.
I checked the cams, and they are untouched- they must have been under a lot of pressure, but it's the rear head that's taken the damage.
But I wanted to try to understand why the incident occurred- simply because when I build the next one I want to be as sure as possible that it won't happen again!
One the (still usable) front piston, there are small marks where (presumably on downchange overrev) the valves have actually touched the piston face.
I know that the cam timing was still set ok, and that the cam chain hadn't jumped a tooth or more, I checked before disassembly. Plenty of oil, too, and the oil pump drive chain was still intact and functioning, so that was another left-field possibility out of the window.
But the touching valve/piston worried me a bit. I had, of course, rotated the engine during a dry build before getting it all locked down, with only the inner valve spring fitted, which allows you to depress the valve until it touches the piston, a degree at a time through the whole of the approaching tdc phase.
So I knew that there was plenty of clearance- at the time I was surprised at how much, because I noted that you could get away with quite a bit more lumpy pistons and cams, higher compression etc.
Not sure how easy it would be to start if you did, thought, but never mind that for now.
So as it's now obvious that touching took place I'm doubting myself a fair bit.
Sure under high revs the con rod grows a little, the valves can move down further than the cam pushes them due to inertia and tired valve springs ( I used standard springs, they seem to cope well under normal revs and I didn't increase the rev limit).
But the more I looked at the heads of the piston that survived, the more confused I was about exactly where the valve was touching the piston faces- it wasn't properly in line with the cut-outs machined into the piston face.
There are two unmachined "lands" that sit at the extreme front and rear of each piston; one land is larger than the other.
It's the same on a standard piston.
So when fitting the high comps I took care to fit them the same way round- there are no "front" arrows, or markings to show inlet and exhaust sides.
Yes, dear reader, I got them the wrong way round when fitting them.....
The larger of the two lands is the opposite way round compared to that of a std Storm piston.
So the valves were not lining up correctly with the machined cutouts, and on occasions were touching raised areas (unmachined areas) of the piston, eventually leading to a bent valve and various mechanical mayhems.
Actually, I'm not unhappy- at least I understand exactly WHY it failed, and I can be sure that it won't affect the next build.
And I'd rather do something stupid on my own engine than a customer's.
Interesting, though, that it survived two years plus of being thrashed senselessly, track day, drag strip, Yorkshire Dales and other meetup abuse- I don't exactly treat it nicely....
Just goes to show how much clearance there really is when fitted correctly, so maybe 12.5:1 is the way to go next time....
And lastly, if they'd been the right way round, wonder how much more power it would have made?
Onwards and upwards, and every little problem is an upgrade opportunity.
I won't be adding more to this thread, apart from answering any questions, as I'll be starting a new one with details of the new build once it gets going. It should be interesting.....
There's a few other little projects to undertake before then, once a few parts arrive I'm giving it lareg with an airbox tub, Flo Commander, and maybe I'll get my finger out with the variable inlet stack thing, oh, and there's ram air to do, but all on the standard engine currently in place, so that I can tell what difference if any those things make before changing too many other things.
Ah, well, nobody's perfect, and it's only money....
It's not falling off, it's an upgrade opportunity.
Quite often it's the simplest of things that catch us out. Rather annoying I'm sure, but at least you can now build the new engine with confidence when the time comes. 
