SOHC.co.uk Forums > CB350/400
CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE - NOW COMPLETE
K2-K6:
I was just thinking the same as you hairy, the amount of carbon visible in the number 1 piston looks like it happened some time ago. Don't know if it's fallen out of the others as you've cleaned them. Seems to have done a decent job of holding compression up though, guess it's a bespoke shape to fit it :)
I'd guess at it happening some time ago. Detonation (yep, pinking) that sounds like if you dropped a M8 nut into a porcelain hand basin from about three feet up so it rattled around. Likely this was previous owner.
Hairy, it understand that piston centre melted is not detonation but pre-ignition that gets the centre of the piston bouncing up and down like a trampoline as it gets hot enough to melt through like you've attacked it with a cutting torch.
Nurse Julie:
Haha, yes, I remember 'pinking' very well, I had a Vauxhall Chevette that did it in every gear under load !!!. What my concern is I suppose, is if it were something I have caused, how can I rectify it to make sure it doesn't happen again? Now, if it was the PO that had it set up wrong thus causing the damage and then me just being the one owning it when it presented it's problems, then I can't change anything to prevent a further failure.
K2-K6:
I messed that up, I should have said dropped from a metre as I was working in metric with an M8 :D
You may have just invented carbon piston rings, could call them graphene in a honed fossilised matrix and claim design rights.
Those Chevettes where quite a nifty chassis with double wishbone front suspension and panhard rod location for a coil spring axle at the rear. Escort owners would kill for something so good, they're still welding bits on them nowadays to get them that good.
Nurse Julie:
The engine blew up on my Chevette going up the old A21 at Polhill in 1982. Got my Dad to come and pick me up, left the car and never, ever went back for it. Could still be there in the undergrowth for all I know but, doubt it ;D ;D
paul G:
Mind boggling how that was still running :o :o :o
Good luck with the rest of it Julie in at the deep end with this one ;) ;D
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