I noticed some scuffing to the rear cylinder when I shined a proper light down the bores this morning. Decided to strip off the cylinders and inspect ...... glad I did!
First thing I found was that there were no spreader washers fitted on the base nuts, and they were not very tight
Pistons havent been fitted with proper oil control rings and none of the rings were gapped correctly, the pair in the bottom groove had seized and the piston is very badly scored!
Front piston has some minor scuffing but the same issue with the two rings in place of oil control ring