Mickly

I’ll let you know when I’ve finished the Trophy engine rebuild 🥺

No problems for me, just watched episode 2 series 3 of Black Sails

Right, I’ve found a place that will skim the head, hone the barrels (& properly clock them) & reseat the valves. I decided to remove the valves myself to have a look at the condition of the seats. obtained a cheap valve spring compressor & oh bugger, because it’s a shim & bucket arrangement it can’t act on the spring coz it’s hidden. So a bit of head scratching & with the help of a modified old spark plug... all 16 out - it got easier as I got the knack, still took 3 hours !! All out, Tagged & bagged. The inlet valve seats lo

Yep

Right, taking @Mr Fro ‘advice I’ve measured all the gaps - I checked that the top ring gap was the same, top middle & bottom down each liner, which they were although they differed across the liners. so it seems that all gaps are within tolerance although towards the top end .... The head scratching continues !!

I think there was a T-shirt that said “ What would Dan do? “

I liked this, Dan Walsh used to write for Bike magazine & combines an easy writing style with bonkers ( maybe true ) adventures.

My pistons don’t look anything as bad as that. The bikes only done 30k so I’m scratching my head about how the compression has dropped, these engines are renowned as being robust, the early Hinckley Triumphs were over engineered to break the link to the bad reputation that the Meridan bikes had developed.

Ah, yes .. the ‘special’ off set cam nut

Good point, I did try to ensure they were square, I’ll measure the distance from the end of the bore to make sure it’s square.

New rings are £45 per piston !! yeah, all the rings were free when the liners came off.

Dunno yet, but the reduced compression was across all cylinders

“Usually” your experience in this matter shows

That’s the conundrum - is 0.05mm above the tolerance enough to make the difference?

Piston number one off looks good? Top ring = 0.35mm tolerance is 0.20 to 0.41 installed in liner Piston Diameter tolerance is 75.96 to 75.98. Actual is 75.98 We might have a winner - the second ring gap is 0.63mm - upper tolerance is 0.56mm is this enough to cause the compression issue?