// Adjusting your tappets

Remove legshield & left side engine cover.
Remove spark plug, to make engine easier to turn over, remove both tappet covers, turn the flywheel, while you turn, watch the tappets, when top one goes down, (induction) keep turning the flywheel, as the tappet comes back up, look for the T mark on the flywheel, this should be inline with the notch on the casing, the engine is now at TDC (top dead centre) on the compression stroke, get a 2thou feeler gauge and put it between the valve stem and tappet, it should be a nice sliding fit, take your time its a very fiddly job, if you have trouble getting at the inlet one (top) I unbolt the manifold at the barrel, slacken the air cleaner hose at the carb, and swing it to one side.

The reason it has to be at TDC on compression, is so the camshafts in the right position, i.e. both valves closed.
remember the 4 stroke cycle, induction, compression, ignition, exhaust, as piston travels down inlet valve opens draws in fuel/air=induction, near BDC (bottom dead centre) the inlet closes, piston goes up compressing fuel=compression, near TDC the plug fires the fuel =ignition, as the piston nears BDC again, the exhaust valve opens, as the piston goes up the exhaust gas is pushed out, =exhaust, sorry if you new this already, hope this helps.

Courtesy of www.fuzzibitz.8m.com & members of www.cubc90.co.uk