Just bought a used 01 yz 426. It has little compression it had set up about a year from last ride. Took off carb held my hand over intake and compression is definately being lost past the intake valves. I pull-started the bike and it ran about two blocks or so till i went to let it idle and it died (did this twice keeps fouling plugs) Anywho took the valve cover off and the I cannot get my smallest feeler gauge .0015 between the lobe and lifter on the intake side (exhaust checked ok .010). could it have gotten so tight that it is causing compression loss. and timing chain is really loose, took tensioner out and seems to be working properly is this fairly common for the chain to stretch that much. can i change just the chain or do i have to change all three gears.