Cathals Yamaha engine. 75hp 2 stroke

[realyriley]

I have problem with smokey engine running rough with low power, running "off" a cylinder, spark ok, new spark plugs, smoke is heavy white with some oil deposits in water, was run at 100to1 petrol /oil mixture, could this have caused engine damage? or does the fuel system need cleaned and run on 50to1 mixture.

Can any one offer some help.

Best regards.