I would like to know how you can adjust the valve timing on this engine.

I appreciate this is an overhead camshaft type engine and I therefore presume that the only way to adjust the valve timing is by shims i.e. you cannot more simply adjust the valve gap by lock-nut and screw adjuster as you would do on a push-rod engine.

Reason I ask is that the owners manual tells me the valve timing should be checked & adjusted after every 150 hrs of use - seems quite often for an overhead cam type engine to me. Also when I tried to take the "rocker box" cover off it proved to be very flimsy and seemed to be a disposible item that would bend if any leverage was applied. I decided to back off rather than risk a new cover just for having a look at the engine.

Can anyone confirm / advise whether I am correct in my thinking on this?

Also does anyone know what the exact valve timing should be (exhaust & inlet valves). Many thanks in advance.
Dommo

The valve timing is not adjustable, if the timing is off you would have to replace the timing belt. Chances are you are referring to the valve clearance, which is adjustable and should be checked periodically to make sure they are within specifications. Adjustments are achieved via an adjustment screw and a locknut.