YTM 200 Problem ( Help Please )

[jempro]

Hi i recently purchased a YTM 200E as a non runner, after hours of trying to get it running it started & ran for 30 seconds then blow alot of oil out of the breather. Blowby the rings i thought so i fitted an over sized piston,rebore & new rings, still the same hard to start then when it does it blows out most of the oil in the crankcase. I then took the head off & had two new valves fitted thinking it was that put it all back together with new gaskets and still the same. When cranking it over with the dipstick out there is alot of pressure comming out with each stroke of the piston.
I have checked the valve timing it is ok & when you do get the engine running it ticks over ok and sounds ok. So has any one got any ideas to what else could cause massive crank pressure to build up.:wondering

[muthey]

time to check the bore job, and see if they bored too much, also check the rings placement, if all that is ok then there might be an issue with the crank. Have you had the head checked for warping yet? These are just some of the options, I recommend a complete tear down and inspection of the entire motor to find out what is wore out.