What oil do you use for a 1986 Honda CG125?

Answer 1

Given the era of manufacture, oils were a lot "simpler" back then. Good old Castrol "GTX" or "Grand Prix" or similar Mineral 10w-40 or 20w-50 will do the job just fine. Avoid anything with "friction modifiers" in it as the clutch won't like it a lot.

The secret with ALL egines like this that do not use a replaceable filter -change the oil OFTEN -if it turns black, you've left it too long.

Also, under the RHS crankcase cover is a "slinger" which needs cleaning periodically if ridden regularly, Annually, at least. You'll need to replace the cover gasket in all probability when doing this.

AVOID AT ALL COSTS using RTV or any form of silicon sealant in lieu of a new gasket. It could cost you your engine. (Don't say I didn't warn you!!)

This is an extremely reliable & robust engine -as long as you keep clean oil up to it. The harder you thrash it, the more often you should change the oil. 1000 Miles max will reward with long life. It doesn't hold much, & the oil does gearbox duty as well, remember.

"Fresh oil is a cheap spanner"