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Didn't know that? I know Matchless/Norton and others shared British tech before they went defunct. The Snorting Norton, here's a Commando 750 gearbox i'm finishing up for a 1973 restoration. Sooo different than the Asian bikes! Think i have all the Andover tools and Whitworth tools for just a one-off endeavor i'll ever need again, but ya never know ha.

Well that didn't go as planned, got the rivets welded in but I got hairline cracks, tig welded it with ER80 S. Anyone know the secret to welding these? Hoping Jay might chime in and share his process??

Welds look burnt.
Probably not enough sheiding gas which has led to excess oxygen causing overheating, over expansion and enbrittlement.
Maybe to many amps too.

Tig was set at 25 lpm, furick #10 pyrex cup

Welder friend used silicon bronze type welding rod on my 750 basket.  He welded each rivet in segments, working his way around the basket.  

P1020585 by nessism , on Flickr

Hmm, never thought about Tig Brazing them in........

Who got nutty with the drill bit lightening the basket? That's probably where your hairline cracks came from, no dispersion material to relieve the byproduct of heat when welding. 

In the Suzuki GS world, drag racers would sometimes scatter clutch assemblies because the backplate would shatter, and/or the basket, although this was much less common.  That clutch assembly full of holes throws a red flag to me, although, admittedly, I'm not a draw racer, and I don't know big KZ's very well.   

I used 304 ss to weld my clutch basket. Sil Brz would be a good choice too.

I don't think you need to be worried about some tiny cracks, you mentioned your planned engine build was going to yield about 140 HP.

It takes a lot more HP than that to rip apart a KZ clutch hub. I was told stock KZ stuff starts to break at the 400 HP level.

You also need to remember the weld material is now stronger than the material it is bonded with. It would take some crazy power to rip that assembly apart even with the lightening holes.

That would be me that lightened the clutch assembly, It's not unusual to do that, I doubt it has anything to do with the cracks, 

I have never heard of a KZ clutch coming apart at the drag strip. The main carnage happens to pistons or drive chains, I have seen some drive chains break and it can cause case damage in front of the drive sprocket.

I got rid of the stock chain guard at the front sprocket, I made a stronger thicker steel guard in case the chain lets go (grey strap) This protects my fuel pump and lines but also the lower case.



The stock trans door cover casting breaks too easy when the chain comes apart. This is on a 650 but you can do the same thing on a 900/1000.