Vire 7 - Bulletin Board

What Petrol:Oil Ratio Do You Use ?

8th July 2001 - Introduction from the Webmaster - There seems to be fairly wide variation. Martin, in Ireland, has one of the older engines and uses 10:1, which he says is smokey. The original small-end bearings in the older engines (up to the middle of 1974, Serial Numbers 20001 to 22000) were made of bronze. The small-end bearings on the newer engines (i.e. from the middle of 1974, Serial Numbers 22000 to 99999, and 00001 to 02999) have needle roller bearings and need less oil. The 1974 and 1975 manuals recommend 20:1 for the first 10 hours and 33:1 therefter. However, RC in New York, USA, has used 50:1, as did the previous owner of his engine, and both were perfectly happy. Please, E-mail the Webmaster and tell us what you use.

Reply #1

Received on 10 July 2001
Posted on 13 July 2001

My handbook, dated 1992 states:-

I hope this is of some use.

Eddie Fitzgerald

Reply #2

Received on 19 July 2001
Posted on 22 July 2001

My Vire is a 1976 or 77 model. I was using 40:1. Recently went 50:1. On this tank of fuel, I have noticed a slight loss of power. I am going to check the plug first and if that is not the problem, will move back to 40:1 to see if that is the reason.
The motor is in a C&C 26

John on Harbinger

Reply #3

Received on 25 September 2001
Posted on 26 September 2001

I have a 1977 C&C 26 with a Vire 7. My manual says to use 1/4 pint per gallon which is 32:1 if my math is correct. This mixture has served me well for over 15 years. Every few years I clean the exhaust port of accumulated carbon.


Reply #4

Received on 16 October 2001
Posted on 21 October 2001

My Vire is an older one with aluminium connecting rod and a bronze bearing in the small end. For three years I ran it on 100:1 oil mix (Fully synthetic, Motul bio-degradeable oil). It was going fine until this Spring when I was forced to use the engine in a boring calm 60 Nm leg. After many hours running, the engine start to misfire. I checked the plug, points and so on; everything was OK, so I went on again. Suddenly I heard an alarming squeeeek, and I realised it was over for this engine.

After disassembling, I found the small end seized, probably due to the oil ratio. Now I have replaced the whole crankshaft with a modern one with needle bearings in the small end, and now I'm convinced that it will work with 100:1 ratio. It has run perfectly all summer 2001, even on long (boring, windless) 50 Nm legs. By the way, 100:1 ratio is almost smokeless with a hot engine!

Mikael Wesala

Reply #5

Received on 19 March 2004
Posted on 8 January 2005

I used 95 octane (or less, when it was available) petrol 33:1 mixture with Super Outboard oil. In emergency I have used ordinary two-stroke oil. I think that modern two-stroke, low ash oil (air-cooled motorcycle) is probably OK from the engine longevity angle although some might say its viscosity is a little on the high side in the low revs, low temperature Vire environment. From Iain Forsyth

Summary from the Webmaster

Posted on 21 October 2001

From what has been said, it seems that the safest course is: -

  1. Use Super Outboard Oil (BIA-BIN's TC-W-N quality) in preference to standard two-stroke oil.
  2. Engines with a Serial number of 22,000 to 99999, or 00001 to 02999, i.e. built later than the middle of 1974, are fitted with needle roller bearings. Older engines (Serial Numbers 20001 to 22000) were originally fitted with bronze bearings.
  3. If you are certain that your engine is fitted with needle roller bearings in the small end of the connecting rod, then a petrol:oil ratio of 50:1 is acceptable.
  4. If your engine is fitted with bronze bearings, use 33:1.
  5. I you ever rebuild your engine, use 20:1 (5%) for the first 10 hours after reassembly.

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