I've just stripped my spare BIS engine to see what its like. I was just going to pull the head but got carried away. It had done about 50,000 miles and was apparently running fine when taken off the road - the nice colour to the valves appears to confirm this. The engine had not had an oil change for a loooong time based on all the sludge which was a bit of a blow. However, the bores were perfect and the pistons show no blow-past. Thus, like Rusty I would double check before buying new pistons as you can likely get away with just new rings and a glaze bust. The crank appears to have survived with just a tiny bit of scoring to the journals but both big end shells and the flywheel side main bearing were down to copper so the poor thing must have had low oil pressure as well. Timing chain and sprockets were quite worn as well. I don't know how much wear on mine was down to lack of oil changes but I reckon a well cared for BIS engine should be able to do 100,000 miles easily.
Keith
