Chainsaw Repair

The Stihl 4mix are definitely true four stroke with a intake and exhaust valve as far as the combustion cycle is concerned.

The oil in the fuel is the source of lubrication.

http://www.stihl.com/4-mix-engine-lightweight-and-with-good-lugging-power.aspx

I have several 4 stroke model airplane engines that use the regular two stroke fuel.

They use blow-by past the rings to lubricate the bottom end. They last as long as the two strokes.

The small Honda four stroke has a impeller in the crankcase that whips the oil all around. You have to have it in a certain position to check the oil.

The 246.4 and the attachment series  Dolmar  trimmers are a true 4 stroke with oil in crankcase and straight gas in the tank. they pump oil by crankcase pressure forcing oil through passages that have check valves for one way oil flow.
the 245.4 and 335.4 trimmers and the blowers don't have the check valve system...Honda system sounds similar to what these do.

the mtd, troybilt, Ryobi 4 stroke trimmers use a dipper system to just throw the oil around.

shindaiwa and stihl have 4-mix system which has no crankcase oil and instead uses mix gas to lube everything. I think they both had some problems in the beginning.
 We have a 4 mix stihl on the farm that is 8 years old or so and other than replacing the carb a couple times it has been great. Since the dolmar showed up it doesn't get used anymore though.

A weak 50cc saw weighting like a 70cc saw, no thanks! 

ok I may have spoken too soon. the 335.4 according to the sales flyer is the 360 degree engine and the product book doesn't list it as the 360 engine so idk for sure which it is.