If you read the book , the pistons last as long as the oil and every consumeable part :-
15 Hours
is that a new piston every 15 hours andy? , had my 2007 CRF250X nearly 2 years, change oil & filter & gearbox oil every 2 to 3 months depending on use, and check level after every ride, have valves checked after first full year of owning it, by my local bike shop, they fitted it with steel valves, but they did think it was strange i wanted them checked even after a year ( they both race crf 250 & 450s) which i thought was strange as everyone harps on above valve checking? also they have told me not to bother with filter cleaner and clean with petrol & then oil, and also i use semi symthectic oil which is the same stuff they use in there race bikes ( morris oils i think)
