Moto Grand Prix
Main Motorcycle: 1973 Triumph TR7RV
Join Date: Oct 2013
Location: Pleasant Hill, CA USA
Other Motorcycle: 1964 Triumph Mountain Cub
Hi Ploughboy, You should buy a bunch of lottery tickets as a lucky man! Or... you used your luck up on the Triumph.
Anyway, I can't tell for sure, but looks like some nicks in head which will smooth out nicely. Same with piston at edge of valve relief.
Good you found the problem & now have a repair path. Glad you didn't bend valves or have major damage.
Regarding the PRT upper seals, that is not from over torque. The torque wrench sets the torque. The PRT seal crush is a product of the thickness of head gasket in relationship to if head or cyl have been skimmed & all that.
Saying that I've seen these red soft seals do that even with proper crush . I'm personally not a fan of them. I personally like the Viton O-rings which can come in any color but from Rabers were usually brown or black.
Push rod tube seal crush is a whole subject unto itself. Did you test crush at assembly? Even .015" is enough. I feel over .035 is getting to the max I like. More than .040" is not recommended & can cause head damage.
The official spec in Triumph Bulletin # 324 November 1969 is crush .030-.040".
Deburring tappet block sealing surface & head bore for PRT is essential to preventing leaks. I usually put a thin smear of silicon on the round O-rings. Still they often will start to seep after about 5 years.
If you have too much crush even with thinner white bottom seals, you might think about thicker head gasket. Solid copper .080" thick.
Regarding air filters, unless you have a specific race track reason to not use air filters, you are asking for trouble. No filters can wear slides, carb bore rapidly also. Where I live you won't cover 3k miles without wear out carbs & cyl bores.
I don't know how that coin got into your motor, but you'd not believe what can get sucked through a carb. Pebbles you'd be certain too heavy to suck in is not uncommon. Again I don't know the size of the coin compared to passing by valve, but small bits are thrown into air all the time by passing motorists. I've had them hit my legs often. A gas cap once. That hurt! I have factory air filters. Always surprises me how much little twigs, bits of grass & insects is in them besides the expected dirt.