Snowmobile Repair: 1973 Suzuki xr400, vintage sleds, vintage sled

Question
ok, my 73 suzuki xr 400 owners manual says to use a ratio of 20:1 for mixture of oil and fuel. it also gives conversion charts for this. for 6 gallons it says 2.4 pints which is i think eqivalent to 1.2 quarts. anyway my freind and his dad said that from past experience with other sleds back in the day , that using that much oil i will be fouling plugs all the time and that i only need half a quart. what do you think i should do. i mean that does seam like a unbelievable ration considering his sleds are 50:1

Answer
Hello Matt,

   I've had 3 vintage sleds over time, and have always mixed 20:1. Out of those sleds, one never fouled plugs, and the other two would foul at times. the problem is, a vintage sled is really old, and needs alot of lubrication. On the other hand, too much oil can cause overheating, just like too little oil. For your Suzuki, I would mix 1 quart of oil to every 5 gallons of gas, if you use cheaper, NMMA - TCW3 type oil. If you use good, fully synthetic oil, 40:1 would be ideal. Hope this helps you. Let me know if you need any help at all. Good luck with the sled! --Arcticatman