hi geewhite............
you don't necessarily have to take off the flywheel cover to set the crank to "T" ( top dead centre ) as you could utilize the cam timing marks on the cam sprocket, lines parallel ( level ) with the horizontal cam cover gasket face............you will notice a "notch" on the flywheel side of the cam which is a pointer to tdc for the cylinders and I cant for the life of me remember if the notch is at "noon" for tdc on the left cylinder?
however it is better to remove the flywheel cover as ign advance and "fine" cam chain adjustment can be checked/done etc.......can you make your own gasket yet?
if plugs out and bike in gear the back wheel can "nudge" the crank ( in direction of rotation, ie anticlockwise ) to tdc.
5 in and 6 thou ex for 250......4 in and 5 thou ex for 400 on a cold engine.
remember if your fighting the cam cover to get it off or on then your doing it wrong, there is a sweet spot...........
glue to gasket ( seal ) to the cover......
with the cylinder to be checked, make sure both of its cams are pointing down.......
insert feeler gauge in gap tween none nutted end of the adjusting screw and the top of the valve.
250 exhaust....if a 6 thou wont go in then its toooooom tight, if a 7 thou will go in then its toooooo slack.........
a 6 thou feeler should slid in with some resistance but not enough to "buckle" and "permanently bend" the feeler..........
note that the clearance will change slightly when the locking nut is done up...........
its a bit fiddle at first put you will soon get the "feel"..........steady as you go.........
inlets are a bit more fiddly as there are 2 valves and gaps, so a feeler in both gaps to finish, they can be set individually to start with.
if the plugs are out you can see some of the valve face and seat......are they black and split or shiny?? and any recessing??
what was the comp test reading with a wet test?? and any "popping back " through the carbs??
how was cam timing "lag".......any non parallel marks or late ( leaning back ) cam timing?
some 2t in the petrol and slow running ( no revs over 4k ) for a while will free off sticky valves........unless of course they need a decoke.......
sticky valves are only a problem if the engine has been left standing for more than say 3 months unless you live in the brasilian humid rain forest, they can stick open usually with terminal results for the engine. even "fuzz" on car rescue knows this, flames through the carb, he breaks tooooo much stuff don't he!!
