Adjusting the valves:
Adjusting the valves is a precise job that need some practice. A too wide valve clearance is not as bad as a too narrow clearance because in case of a too narrow clearance it can mean that the valves never close completely and that means that the valves can not disperse their heat via the valve seats and therefore they will burn.
Correct valve clearance:
intake valve: 0,15 mm
exhaust valve: 0,20 mm
Remove the valve covers by removing the valve cover nut in the middle of the cover and both M6 nuts (and rings) between the cooling ribs on the cylinder head.
Remove the locking nut on the rocker arm and put the correct feeler gauge between the valve and the rocker arm. When turning the engine (allen key in rotor retaining bolt from alternator) the feelergauge will fall when the piston is in the top position.
Put the feeler gauge back and torque the adjusting screw by hand till the feeler gauge.
When the engine makes a turn the feeler gauge with the correct size must stay in place while a feeler gauge one size smaller must fall out when the engine makes a turn.
Tighten the lock nut without turning the adjusting screw and repeat the last step until the valve clearance is properly adjusted.
Repeat this procedure for all the four valves and don't forget that the exhaust valve has more clearance because it becomes hotter.
When the gaskets are in bad shape replace them and put the valve covers back in place.
When a valve revision has taken place the valves have to be re-adjusted after a pretty short time when the valves are properly seated on the valve seats.
When the cylinder(head) has to be re-tightened this has influence on the valve clearance so this has to be done before the valves are adjusted. This also means that the valves have to be adjusted every time you re-tighten the cilinder(head).
(c) W.P.Barendsen 2000