Hi all, with 2 strokes after 1980 the bearing tolerances etc have been trimmed down.
With 30 years plus worldwide 2 stroke race engine building/tuning experience there are a few rules to make sure your engine is reliable.
1. DO NOT USE 4 stroke oil. The esters will not mix with the fuel easily and it causes friction on the bearings, rings etc. No lubrication. It pools in the crankcase and makes it hard to start.
2. Only use 1 type of 2stroke oil. Never change brands, grades or mineral to synthetic. The oil causes certain wear properties to the parts, changing oil type/brand/grade can lead to premature wear or engine seizure. Only chage oils at rebuild time.
3. Always err on the too much oil side. Easier to de-coke than it is to rebuild.
4. Buy the best oil you can readily get. Local garages etc. No good running out of oil and only 4 places in Australia sell it. Castrol 2T is available everywhere, mower shops, bike shops, jetski shops, garages and so on..
5. With 50cc oil injected scooter's you should put 5ml of oil for each litre of fuel in the petrol. The oil pump cannot supply enough oil at sustained high rev's to keep the engine lubricated properly.
With my mojo 50cc scooter I have removed the oil pump and run pre-mix at 65/1. I use GRO go-kart oil.
Lastly you should not use 2stroke oil in 4 stroke bikes as the clutch/gearbox on most 4stroke bikes uses the same oil as the crank, pistons. 2 stroke oil in a 4 stroke causes heaps of problems, clutch slippage and bearing knock come to mind.