Best Octane for 1957 M72

[Eastwest]

Hi. In the process of tuning the bike. I have been using 98% Octane. Is that the best for this bike? Here in Australia the choices are 98, 95 or 91%.

 

Mark

Ps. Have added a little more of the bikes progress to my project thread here.

[haj]

The bike is made for something like 67 octane. so 91 should be fine.

 

I'm running 92 unleaded in Denmark, and it seems to be all right (It's been a while since I checked the valves though, and they are the ones that might like a bit of lead afaik)

[Eastwest]

The bike is made for something like 67 octane. so 91 should be fine.

 

I'm running 92 unleaded in Denmark, and it seems to be all right (It's been a while since I checked the valves though, and they are the ones that might like a bit of lead afaik)

Lucky I asked then. Good point you make about running unleaded in this old girl. I don't want to burn her out. I wonder if that fuel additive is still available to make it leaded fuel or its equivelant. Will contact some auto stores today.

 

Mark

[haj]

Forum question;

My feeling is that lead (or additive) isn't actually that important (at least for the sidevalves) .. anyone else feel otherwise?

[Mike Goldthorpe]

I've been running my R50/2 BMW on 91 octane unleaded here in NZ. Seems fine after 8 years....

[luca.stere]

I know an Ural M67 with more than 80.000km runing with 95 unleaded fuel with no problems. Also, in Romania after 1990 we still had for 15 years old cars which have running with uleaded fuel up to 200.000km with no problems.

[Eastwest]

I remember when unleaded fuel was introduced. It was such a big deal and everyone was adding chemicals to their fuel and rebuilding the top of their engines.

[luca.stere]

I remember when unleaded fuel was introduced. It was such a big deal and everyone was adding chemicals to their fuel and rebuilding the top of their engines.

 

Probably just fooling the consumers.

[Solly]

As I understood it was hard to get a lubricant to the then valve guides made of iron or steel of the like. So they added lead which wouldnt smoke or foul plugs. The guides of modern era are more self lubricating materials......hardened bronze or mixture of those kinds of metals. No more lubricant required. But I believe they still have some sort of additive to lubricate in tank fuel pumps and injector pintels.

[luca.stere]

As I understood it was hard to get a lubricant to the then valve guides made of iron or steel of the like. So they added lead which wouldnt smoke or foul plugs. The guides of modern era are more self lubricating materials......hardened bronze or mixture of those kinds of metals. No more lubricant required. But I believe they still have some sort of additive to lubricate in tank fuel pumps and injector pintels.

 

My father was a mechanic and told me that he learned at the mechanic school that the lead was to improve the qualities of the gas in order for the engine to run smoother and to prevent unwanted detonations. Also, in the '80 my father was instaling LPG sistems on cars and the LPG gas don't lubricate nothing and the engines was running well.

 

Me and my brothers we have cars with LPG sistems and the engines have many kilometers whithout any problems.

[Solly]

That is true....lead does have a cooling effect in the combustion chamber which could only reduce temperatures which cause predetonations. Not sure of the LPG thing. But do know when working for Ford that the Police cars that were running LPG or CNG seemed to hole out a piston unusally more often than other vehicles. We were pushed to put in synthetic oil.It did make a difference.

[luca.stere]

But do know when working for Ford that the Police cars that were running LPG or CNG seemed to hole out a piston unusally more often than other vehicles. We were pushed to put in synthetic oil.It did make a difference.

 

It was a problem from fuelling mixture, poor LPG mixture which result on blue flame with high temperature. The problem it was not the LPG or CNG itself.

[Bilge Keel Dave]

Tetraethyl lead is an octane booster, not a lubricant, it was introduced to gasoline in the 1920's and phased out in the 1970's because it ruins catalytic converters.

Another thing it does is to prevent micro adhesions between the valve seat and valves on some engines with cast iron heads and valve seats. The micro adhesions cause valve seat recession or excessive wear of the seats.

[Solly]

I knew about the octane boost that it gave. Thought for sure it had a lubricant quality to it though. Could be wrong.

[Solly]

I knew about the octane boost that it gave. Thought for sure it had a lubricant quality to it though. Could be wrong.