Motorcycle Repair: Cylinder failure yz450f 2009, wiseco piston, bike repair shops

Question
Good day Gary
First of all I would like to thank you for your time concerning my question.
I have a problem with cylinder failure on my YZ450F. I only do casual riding. I am a technical analyst on earth moving equipment and do have good knowledge on mechanical operations although this is not to say I know exactly what to do on a motorcross bike. I took my bike apart to re-plate the cylinder as it was glazed. It was re-nickasiled at a company that do work for various bike repair shops in South Africa. I received the cylinder and re-used the standard piston with a set of new rings. At the first start-up there was a noise that seemed like a timing chain scratching. After numerous attempts the bike was again torn apart. The marks on the cylinder was in a vertically direction and seemed if the plating dislodged from the cylinder. The plating was then again done and a new wiseco piston and rings was inserted. Oil drained etc to have it all done properly. The people however had taken of just too much from the cylinder top area after nickasil and the piston just touched my head area. The noise was not loud and seemed like pre-ignition. I drove the bike (after good running in period) and decided that the noise need to be dealt with. When opening the engine the I saw that the piston touched the top and the cylinder again showed the same failure marks as previously although it was not that severe as the first time. I was using a synthetic based oil at the time API SG 10W40.
Any information will be gladly appreciated

Regards
Luan Fourie

Answer
Luan,  I have built a few of these and some quads in this size. Here goes.. The piston is to close to the head as every thing heats up it expands and may do some horrific damage. The piston has to be fitted to the cylinder with only about .002" clearance at the skirt.If the cylinder was decked at the top to up compression to much may have been taken off. With the cylinder in place place piston at TDC to see what kind of clearance you have.If you dont have enough some times approx .035" can be milled off. You can also do a clay test. Install piston you dont need the rings for this install cylinder and place a small amount of play dough or clay on top of the piston. Install cylinder and torque down. Rotate engine over and smash the clay then pull top end off and cut the clay and measure the portion stuck on the piston.This should give you an idea of clearance or lack of it. Some have gone as far as two base gaskets to raise the cylinder for piston and head clearance but only to find the timing chain tight to get on.