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trouble shooting 99 wr 400

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so a while back i got a used wr400f motor and threw it into  my street legal yz400f i thought a wide ratio transmision and the wr stator was a big plus. i had it run and stall out in the past never to run again, i did things like put a yz450 carb and shim the valves- no start and no bump start worked, it had spark and i dumped fuel in the plug hole it would not fire. yesterday my kid brought over his new leek down tester it took less than 5 min to figure out air was getting past the piston because we could hear air in the timing chain galley , cam caps off and cams out we could hear air in the intake and the exhaust. what a great tool to have if your trying to figure out if a motor is any good without tearing it down.

i guess 175 bucks i got what i paid for lol, i have new valves , guides and seals on hand so here i go again to the machine shop.

is the difference between a 400 and a 426 noticable? my 400 cylinder looks ok but measuring will tell for sure, are the 444 big bores reliable? what to do its old and i dont want to dump more into the motor than the bike is worth

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