Hi,

>Given many 125cc bikes use just 1 litre of oil, it might be getting a hard life with a fairly high revving engine. On My Grandsons Yamaha, i used the highest quality synthetic oil at about 14 pound a litre due to his lack of any bike knowledge. I used to oil change it every time he turned up at my house. There is a very crude oil filter on those 125s.

One of the Hondas I owned when dispatching was a dearly beloved 250RS single. It followed a (late 1970's) Dream twin - the twin had 2.5 litres of 10W40 and a proper full-flow filter, the RS had 1 (or 1.5?) litres of 10W40 and a tea strainer "filter" about the size of a postage stamp ... Both did the usual Japanese thing of swilling the engine oil 'round the gearbox but, in addition, the RS had a roller big-end. Honda "recommended" the same 1750-mile oil-'n'-filter change intervals for both ...

>high quality oil would be a good recipe

I used the best I could afford and changed it every 1000 miles but sadly no synthetic available then. Also I got the bike with over 65K on the clock and a broken speedo. cable so iirc I only got the bike to about 75 Kmiles before the big-end rumbling became too loud. Sold it to a mate with more expertise of fixing old Britbikes with roller big-ends on built-up cranks. He fixed it in the end but he said Honda had put in several gotchas to deter all but the most bloody-minded from fixing 'em.

Amazing any 250RS have survived ...

Regards,