Mculloch MT300x Strimmer will not run at full throttle?

Hi,
I have obtained an old, good coniditon2 stroke petrol strimmer.
All parts look functional and in goods condition.
When I start it it runs at slow tick over but as soon at I open the throttle it cuts out.
It sounds like it could be a fuel supply problem and I can see on the carb only an adjustemnt screw for slow running, there is two other what look like like adjusing screws but I am not able to move these.
Can any one help, is it possible to e-mail me an instruction / service manual??
I know this is an old model engine but I would think that McCulloch would have used this design of two stroke engine on many later and possibly current tool systems.

Regards
Bill