Premix Question?

[birddogg]

Working on a friends 85' 250R and wanted to mix up some fuel for it. He bought some Amsoil synthetic that has a recommended ratio of 50-1. The R says 20-1. I haven't owned a 2-stroke in 20 years and I don't want to give bad advice to a friend. Shirley one of you guys are up on the newer lubricants.

All I remember is that one bottle of MC-1 mixed up 6 gallons of fuel for my old YZ.

[Mr_RPM]

threw the years 2-stroke oil has gotten better and therefore less is needed. the 250 says 20:1 because at the time it was made the oil quality required that much. now days with normal oil its basic to mix at 32:1, and now with synthetic oil you can run as little as 50:1. if it was mine I would run it a little rich and maybe somewhere between 32-50:1 on the synthetic oil

[birddogg]

That's what I was thinking. I don't want it fouling out left and right, but I don't know the condition of the engine and don't want to seize it either. He says it's all original and I believe it. Still has the original grab bar on it. Skid plates are intact and in good condition. Really clean machine.

[3Razors]

If the bike is completely stock including the jetting it will run best at 20-32:1. That is the oil ratio Honda engineers set the jetting at.

[DixiePlowboy]

That's what I was thinking. I don't want it fouling out left and right, but I don't know the condition of the engine and don't want to seize it either. He says it's all original and I believe it. Still has the original grab bar on it. Skid plates are intact and in good condition. Really clean machine.

Plugs are cheap....though more indicative of your jetting than your oil content. Cranks and pistons....not so cheap.

I don't have the exhaustively detailed studies of oil ratios bookmarked that explain the many reasons why the "50:1/modern oil" theory is wrong, but the data exists.

You actually lose horsepower with the higher ratios anyway, but that's not the only reason to make sure everything that needs lube is getting lubed.

I run 32:1 for all around riding with periods of both fast and easy riding. For long periods of full-throttle or racing I'd mix in a bit more oil to make sure the crankcase never runs dry.