BTW I just took a look at the link posted. the "test" was pretty flawed IMO. Using a aircooled oil in a light load, low temp, constant throttle application like this will lead to carbon buildup. Counter to what the author claimed you need a high cylinder temps to burn the fuel oil mix completley. I have seen motors ran for 100 hours on MX2T that showed a slight, thin carbon pattern, with bare metal where the transfers dump in. The ring land area was bare metal, the exhaust pipe was spotless, the exhaust port had only a few spots of build up where the exhaust flow eddyed,and the area under the piston crown was clean as well.
Another thing to consider is the port arangment has a great influence on how clean the motor runs. Stihl and Husky chainsaws are a good example of this. A Husky saw will run very clean regardless of load and carb tuning(to a point, while a Stihl has to be tuned pretty close to the edge and be loading substanially to burn clean. Another example would be my the cr500 motor in my bike. It has stock jetting with the exception of 1 leaner pilot and the air screw adjusted daily and it burns so clean at 32:1 its scary. The honda cr 250 I had previously was the complete oposite.
A motor with poor transfer efficiancy will always be dirtier than one with a more efficiant port setup.
