Fuel/oil mix

[gorm]

The manual says for the 502 to run a 25/1 mix. My neighbour has a bunch of old sleds and he said with the new oils he is running 40/1. What is everyone else doing?

Garth

[cdnprairie]

Hi Garth,

I spoke with Bruce awhile back on just this topic. He tells me he runs 25:1 in his, although he tells me some run as low as 40:1with no issues. Myself, and Bruce think along the same line. That is to run richer just to be safe. Other members, if you know something different or use a different mixture, please post a reply.

Ken

[mike1937]

most oil company,s tell to mix it to factory spec there was a company back in the dat that said they could run 40 :1 they went out of bussness rebuilding blown engines mike

[Barrie2777]

The recommendation for the JLO is 16:1 but I run 25:1 in my JLO 252 and can run all day at full throttle but you must be sure that the mix isn't lean. It is the gas that cools the piston and more problems will come from overheatiing than from poor lubrication.

[Roy Teske]

I've been using 40:1 with no problems. Just don't lean out your carb to much . I found I had excessive oil leakage from the exhaust at 20:1 . Most small engine advice I've read on this subject says modern oils are much better. If you take out an engine, it's probably not the fault of a 40:1 mix. Roy.

[slotcycle]

I have dicussed this on this site befor, and here is my 2 cents...

the stock hirth piston on the 300 has 3 rings. If you run a mix too lean, say 50:1, its possible that the middle ring may not get enough oil, and as the engine gets hot, you could lose power. This happened on my buddy"s 300 in a 67 panther. we couldnt figure it outtill someone recomeneded we mix the fuel at 20:1. after that, we had no problems. Similar situation with my Evinrude. I ran Amsoil at 80:1 and lost power. I've talked with a couple engineers about this problem, and they said the middle ring doesnt serve any function, that it just floats between the upper and lower ring and doesnt provide compression. It actually slows the engine down. as a result, I put one engine together and ran a compression test. then removed the lower ring and tried the test again. The compression was the same. Replacement pistons have only 2 rings, and allow the engine to make more power with less resistance. I did assemble a 372 Hirth with olny the upper 2 rings and ran it with no issues.

Matt

1 Diablo, and 20 other weird sleds.

[beefyl]

Hi,
I agree with Roy. I use 40:1 in all my sleds with no problems. The 16:1, 20:1 mixtures were on the real old sleds but if you remember back then most of the time they used just straight 30 oil not 2 cycle oil.
That's my two cents. I've been working on these things for 40 years as a mechanic and never had a problem with 40:1.
Thanks, Beefy

I have dicussed this on this site befor, and here is my 2 cents...

the stock hirth piston on the 300 has 3 rings. If you run a mix too lean, say 50:1, its possible that the middle ring may not get enough oil, and as the engine gets hot, you could lose power. This happened on my buddy"s 300 in a 67 panther. we couldnt figure it outtill someone recomeneded we mix the fuel at 20:1. after that, we had no problems. Similar situation with my Evinrude. I ran Amsoil at 80:1 and lost power. I've talked with a couple engineers about this problem, and they said the middle ring doesnt serve any function, that it just floats between the upper and lower ring and doesnt provide compression. It actually slows the engine down. as a result, I put one engine together and ran a compression test. then removed the lower ring and tried the test again. The compression was the same. Replacement pistons have only 2 rings, and allow the engine to make more power with less resistance. I did assemble a 372 Hirth with olny the upper 2 rings and ran it with no issues.

Matt

1 Diablo, and 20 other weird sleds.

[HUS-SKI ED 1961]

Mike,
What is the name of the Company which went broke selling 40:1 oil and when.
Ed