Forum

[Martin]

Having spent years of wasted time with worn out two stroke
enduros and abandoned outboard motors that eventually ran,
but with feeble power or limited revs, I found virtually ALL
had faulty Crankcase seals. Since the two stroke principle
requires the same compression to function as the piston
and bore, the air cleaner issue is just pissing in the wind
Good news is Mr. H has the seals so you can order them with
the piston rings and gaskets you will presumably be needing
too

[Norm]

A running Ensign, amazing.

[simon]

My little Berini Cyclemotor engines were very lacklustre until I decoked the silencers. Now I can barely hold on!

[apparently lucky eddie]

Why are you using a straight 50 grade oil intended for old 4-stroke motors instead of a decent modern 2-stroke oil?
Also to endorse Gordons comments, the crankcase pressure is essential and of course has to be at cylinder pressure so even the smallest leak will kill performance. You could check for leaks using the old gas-fitter standby of a cup of washing up liquid and water, splash it on to the crankcase joints and look for bubbles. I recall BSA Bantams frequently leaking from the front of the cases just below the barrel. Easily fixed temporarily with some instant weld or araldite but new gaskets and seals are usually required on an old motor. Also make sure the exhaust is free of carbon, block up one end and fill with caustic soda and leave overnight to loosen deposits.