Dear all, the final part to this story
So yes i bought the bike as I had an excellent low mileage engine to put straight in it. The original engine which I didn't bother even trying to start has sat in the corner miserably since it came out. Today in a mad five minutes I thought I would take a look at it. It turned over okay, no nasty noises, no grinding etc. Valves in right position, off with one set of valve gear, rotate and did the other. What no bent push-rods
Undo head bolts, lovely. Nothing much to see in there on either piston just a faint scuff on the front exhaust valve and the rear inlet valve. Anyway with the strain off the cams off comes the cam chest cover. Oh, perfect, no broken teeth, oil pump drive perfect, cam bushes perfect. Okay so back to the pistons, and all seems good in there, not even much wear to be seen, I haven't measured it yet. Having the heads off it was only two minutes to get the marked valves out, they are both slightly bent, just enough to stop them seating.
Okay so lets go back to the start of this story. It says "Anyway. I'm on the M8 extension last Saturday, the bike has an initial loss of power - hundred meter maybe - before cutting out and coasting to a halt. Recovered home on a lorry..." The giveaway is the M8 EXTENSION part. I would like to guess that having the bike with a shed load of revs on-board on the M8 EXTENSION one may have selected an incorrect gear that tipped the old girl well past the redline / rev limiter. This duly made things mash together indoors on the top end bending two valves one in each pot just enough to lose compression.
So we cant blame the oil pump drive for this one
The heads are now being sorted in the machine shop and some new valves fitted. I just thought it would be a good post to show what made this XB12 develop this...
" 30psi on the front cylinder and nowt on the rear... The pessimist may well have been right."
Remember a size 11 boot can make it happen
Could shortly be seen in For Sale in bits ! One lump or two