I just bought a 1972 olympic 300, just wondering what ratio the oil should be mixed.

20 : 1. Use $3.49 a quart Castrol mineral oil. Synthetics do not stay suspended in the gas.

20:1 was the ratio back in the day.

You can run 40:1 and even 50:1 with today's good quality oil (Shell Advanced, Bombardier Oil, etc).

Best bet is to go by the spark plug - if it is oily, then too rich. Always better to run a bit on the rich side as it is better to foul a plug then to pop a piston.

If a motor has not been run in a while, I like to run 32:1 for a bit.

How do I know for sure what year it is? Is it in the serial number? I will try to post up a pic soon.

Clearances of old motors require more oil.

Year is in the serial number....but if it is a 72, then the build year will show as 71. If it says 72, then it is a 73.

Just Post the serial number and I will tell you what you have.

AL

Hey there. Dont mean to bump in, however....
I picked up what I believed was a 1970 Oly 335 (serial number 7112636328). By your suggestion, this sled should be a 72. However, it has a state registration sticker on it expiring in 1971. Any thoughts? Thanks.

You have a 1971 Olympique. It should have a (type 337) motor 335cc.

I use 40:1 to 50:1 with synthetic oil on my old Alpines with no problem. (2.5-3.2 oz per gallon) They are used, sometimes pretty hard, for grooming. The synthetic runs cleaner & don't foul plugs. Turn the key or pull the cord and any of the 3 start right up & idle nice.
1970 640, 1971 399, 1982 640.