Listerjag Posted March 18, 2021 Report Share Posted March 18, 2021 What would be advise re oil fuel ratio with synthetic oil for my Ossa 250 MAR please? Alistair Quote Link to comment Share on other sites More sharing options...
keychange Posted March 18, 2021 Report Share Posted March 18, 2021 If you end up running say 50:1 then you may need to allow for the richer mixture ie: more fuel : air. Quote Link to comment Share on other sites More sharing options...
Listerjag Posted March 18, 2021 Author Report Share Posted March 18, 2021 Thanks for your reply. So if I am running 80:1 with present jetting I would need smaller main jet? Quote Link to comment Share on other sites More sharing options...
keychange Posted March 18, 2021 Report Share Posted March 18, 2021 Less oil means more fuel in the mix, it’s only small but should be considered Quote Link to comment Share on other sites More sharing options...
millwright Posted March 18, 2021 Report Share Posted March 18, 2021 More oil = better piston sealing = more torque i run 30/1 Putoline MX5 in my Bantam back in the day my Maico 125 road race ran 16/1 Castrol R40 got 2nd fastest through the TT speed trap. Be careful what oil you use some of the latest oils are designed for water-cooled engines running at 60c air cooled engines run a lot hotter the max temperature i have found on the exhaust port on my Bantam is 180c. 1 1 Quote Link to comment Share on other sites More sharing options...
Listerjag Posted March 18, 2021 Author Report Share Posted March 18, 2021 Thanks, I hadn’t considered the ring sealing. I’ll see what’s available oil wise around here. Quote Link to comment Share on other sites More sharing options...
djr Posted March 19, 2021 Report Share Posted March 19, 2021 I mix 40-1 full synthetic in my Ossa MAR 250, I did originally use 50-1 , but the bike seems to run better and less hot at 40-1 just my opinion , and you will get people swearing by 80-1, 100-1 etc. as well as ring sealing , the oil can absorb some heat as it passes through the engine , and most importantly - bearing lubrication , some old 2 strokes have bearings that are only just up to the job, so less oil could be the last thing they need Quote Link to comment Share on other sites More sharing options...
Listerjag Posted March 19, 2021 Author Report Share Posted March 19, 2021 Thank you. Quote Link to comment Share on other sites More sharing options...
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