well what type of adjustment will u be doin? if u are cuttin u need a bore cutter so bring it to a dealer. personally i would bring it into a dealer cuase [censored] happens and u could be [censored]! so i would just bring to a dealer and have it done fine no problems!
u are just looking top adjust the valve to rocker clearaance correct? if so do it yourself, takes 15 mins. did it on the 400ex last night. bring the pistion to top dead center on the compression stroke. there are two covers on the left of the motor when sitting that screw out. one is roughly the size of a thumb and the other about a 50 cent peice. the bigger one allows you to turn the crank and the small one lets you see the outside of the staor with marks labled t and f. t is what you want.it is after the f. there will be no stress on the valves at this point and this is where you want to adjust them at. you will need a feeler gauge. on the 400 its .004 for the intake and .005 on the exhaust the intake can have less clearance due tothe cooling of the intake charge and less expansion of the valve is taking place. slide the feelr gauge between the rocker arm and valve. there should be some resistnace , not to much, not to little. as if you turned it out just a hair it would slide freely, that is where you want to set it to. jsut enough so there is resistance. it should not slide freely. on the xr350 it was .002 for intake and .003 for exhaust so you should be somewhere in this range. if it is too tight the valves will open prematurely on the intake and the exhaust will burn up because there will be no play after expansion. if you have anymore questions email me at firstname.lastname@example.org