Just a quick question? Is the plug really black and carbon fouled or is is it getting a fine hair of carbon across the gap?I doubt it would be rings cause I regularly see these mowers with really low compression before they start playing up.Your fuel mix is right but what plug are you using?Older powertorques used cj8 latter ones use cj8y.Make sure you use the thing flat out thats why victa put stop start and run only on the throttle control cause two stroke are not very efficient at low rpm.only things that cause running rich that have not been discussed are main jet (victa have used different ones over the years they are denoted by circles on the front of the jet) most common jet has flat face with just screw driver slot.I have come across jets that have been drilled to stop machines over reving.Air leaks at manifold and starter sometimes cause fine hairs of carbon across plug.Also take the starter off and see if the crankcase is full of carbon.If it is its usually air leak at the starter
