Engine Fault?

You almost certainly have a carburettor fault, it may well be that a carb overhaul kit is available - try e-bay. I wouldn't worry too much about the piston discolouration at this stage- as the engine runs- it is probably just varnish buildup and a change of 2 stroke oil in future fuel mix may clean it off. this is common on 2 stroke engines. before you spend money on piston/rings do a compression test - should be around 90 psi peak. Makita technical in UK are helpful tel 01908 211678 ask for Chris Wright

Martyn
August 2010