Ya know, I use to be a believer in 2 strokes, infact I still am, however, rebuilding a new four stroke motor really is'nt all that different than building that 350 four bolt main we love so much, or that 440 six pack, or that 351 or 429! Its the same motor, just smaller with overhead cam(s). The good thing is there not EFI. Yet. I was a little shocked to see the prices on valves and junk like that, especially the price of a good aftermarket pipe. BUT, some of these Japan based companies have given up on making good 2 stroke engines. Remember in 1994, the KX 250 that was made? My friend here in PGH still HAS one, with the original reeds, only one top end ever was put into it. We named it Christine! And that bike has lasted. Over all the other smokers we had in the last 10 years, that one was built to last. I now am getting rid of my new 2006 CR 250 because the motor already needed 1200$. Im going four stroke now because of the low maintinence. If you keep these machines well oiled and maintaned, they will last.