Yes swisheroo, thermal expansion differences for sure but also these things also just plain flap and shake and shift on their seams even mildly treated, but, ugh, just one kicking up of heels or long haul no let up so no re-torquinh and the sealing turmoil begins again. I hear the stories of oil tight wonders so trying to match em.
11+ CR stayed tight in my ole P!! at ridiculous young greenhorn rpm, but was special constructed and assembled engine, not my fumbling. I suspect Trix could get away with 87 oct. d/t the 2S cam over lap and maybe almost kissing squish gap, what little there is in Combats. Again I'm pretty kind to Trixie and have to use 87 routinely. Tune and throttle hand can match or beat 'puterized retard and fuel injection compensation, sheeze. Trix is gal next door, ok for a good time but not taking on a Ninja death squadron single handed, in the dark, in the rain, off road, that's Ms Peel's task, sheeze.
CHO Head was redone last year by Micheal Starky of British Toys in NC, a life long picky tricky crowd pleader and solution worker. He also did Peels current head with the bronze spacers instead of spring to center rockers over Kenny Dreer's valve kit with new seats cut right. So yes I've considered guides and seals but theres oil on my LH side cover and head seam, ugh, prior it was on R side, not much last rides, so must 1st assume head gasket and maybe even gas jet grooving from chamber to tunnels. No smoke shoots out head, been there done that with flames too on Trixie in '06.
Simplest way out would be a good flamering, now I know what to ask for, smear of copper coat or metallic paint plus some type of good thread around the tunnels and hole drain. Silk or cotton as the synthetics melt and contract in beads leaving gaps or flatens out and doesn't rebound so leaves a weak gap in sealant that eventually fails.
Next simplest would be base plate to make up geometry of missing gasket. Reasoning is less pressure to resist at base, even is about as much shifting and twisting and gapping as head. I'm a bit piffed with even Hylomar at this point but less so that gray thick stuff that acts more like starch when compressed, ie: kinda solidifies and fractures. The tary stuff seems to get too soft with heat then stirred to flow away by the vibes.
Hardest would be doing it like Peel, no base plate or gasket, then diddle the pushrods shorter and relieve pistons for valves and head for pistons. Closer clamp force, no crush material and less thermal shear/shifting plus half the planar leak surfaces with better heat flow.
If turns out to be the head, then i hit a bit of quandary. Spare small port head on hand was the key ingredient in past Ms Peels sport bike hunting hobby. Spare bigger carb and dialed in 2-1 header/megaphone just sitting around too. Must resist as neither me nor Trixie is up for that sort of spunk w/o special preps to handle it. Trixie is my Gulf Coast low octane bone stock tramp.
I would not be the 1st to go naided head on a Norton. hm.
