Some bikes do not like some oils...
beats me. i borrowed an old prolink xl250 off a mate in the early 90's and ran around on it for a month or so then decided to change the oil and give it a once over... i put new shell oil in it and within 2 weeks it had scoured the rings and was smokin like a 15:1 castor special. shagged it totally.
i could see an old CZ struggling with new synth oils but the nickasil bores like the synthetics ok.
Silkoline.. great oil. ran my old Husky (it was new then
) on 50:1 back in 1985..people freaked but it ran well and was well within service when i tore it down after a season of racing but the pro comp oil had a octane booster and it had a good kick over the std stuff. found it hard to hang on by the end of a long day in the saddle
.
Summary: any good oil tts/ motul / etc at 30 - 40 :1 will be fine in all two strokes
fully synths can be safely run to 50 - 60:1 depending on your comfort level...
older castor styles 20: 1 enjoy the smell!!
does that sound right