it might be helpful to actually measure your combustion chambers and and the pistons to see what you actually have for compression ratio rather than rely on what everyone thinks they have.
There is a variety of ways to do this and the info is readily available on how.
Pro engine builders use a kit you can purchase but for the home mechanic you can make up your own
(dont raid the missus cooking equipment).
Published CR can vary widely with real world data not to mention if the head or cyl might have been skimmed in the past. Adjustments with limited piston choices can be addressed in other ways but each is a complicated topic I wont get into here.
Fuel quality of course has significantly changed from 50 years ago as well as what makes up what fuel is today which is a very complicated witches brew of chemicals. Complicating that regionally petrol blends differ as well as seasonally.
It seems inevitable someone mentions aviation fuel (AVGAS) and lets skip that discussion. Its not compatible with your bike, It WONT make it faster, and in most places its illegal to use on a road going vehicle. I have used it blended with some other fuels and chemicals when I was racing as an alternative to off the shelf race fuel but thats a complicated topic and suffice to say ITS NOT A GOOD idea in a machine like yours. Whats good for a recip acft at 10,000 feet in known icing conditions is not formulated for your old tractor engine at sea level or not far from it.
(I am a FAA licensed A&P tech and I can legally purchase AVGAS)
When I was in Europe and the middle east I had considerable problems with fuel quality in my hot rod car. Several friends and I experimented with a alcohol injection system into the carbs and it worked, but was fiddly and not for the masses. The reason we did this was we had non stock engines and that gets into big ports, big valves, very lumpy cams with lots of overlap. A stock car wont have noticeable issues on that same fuel. A super rocket DOES have a very lump cam, and can suffer the same issues but the injection system to work with your old bike is not feasible... I only mention it because the tech does exist and DOES work as opposed to adding alcohol INTO your fuel tank.
I still have some degree of the same issues today with modern fuel. A high performance car engine with certain cam profiles does not tolerate poor fuel, and especially anything oxygenated with alcohol.
Here in the US we have some very misguided policy decisions about environmental issues and while well intentioned and some ways very much needed, Science and politics clash so we are stuck with one of the biggest scams and con jobs in history. I wont rant excessively on this, but its about farm subsidies, Oil companies and crooked and stupid politicians. Billions and billions of dollars every year.
But its best to try and avoid any fuels with alcohol present. In my area its typically 10 to 15% alcohol added to our fuel and they want to go to higher levels. (20% I think) and it plays havoc with fuel systems, Its hydroscopic (LOTS of water, both in storage tanks, as well as collects in your tank) It corrodes all aspects of the fuel systems as well as soft parts such as lines, floats (Rubber,nitrile, plastics) and it clogs small orifices. The smaller the jets and orifices the more problems.
I know for a fact that our state govt has instructed employees to not use these fuels in any state owned equipment and especially mowers, chain saws, trimmers. But this is Ironic because it mandates consumers use these fuels instead.
There are several websites you can access for locations of fuel centers that have alcohol free fuel and I keep a list of them for western US. My wifes car gets 15% better fuel economy with alcohol free fuels and its worth the extra cost. The irony is diluting our fuel with alcohol its a huge profit for merchants and oil companies as alcohol costs a fraction of what gasoline costs.
See:
http://www.buyrealgas.com/See:
https://www.pure-gas.org/extensions/map.htmlIts been a long time since I was last in Europe but I understand there is similar issues with fuel quality there. If you cannot find alcohol free fuel, buy the highest quality you can and separate the alcohol yourself. Several websites show you how. Consider a fuel treatment like STABIL for fuel that sits for some time. (It DOES go bad!)
You can test fuel yourself,, its a simple test using a graduated cylinder and many websites that detail how. At one point I carried a test kit in my car and tested frequently as fuel quality varied considerably and the govt test programs went away so vendors were free to sell some real garbage to consumers.
(** Some places test the pumps for accuracy as well as fuel quality,, Some dont. You know you are getting ripped off when you go to fill up a nearly empty 12 gallon tank and the stations pump says they sold you 15 gallons!
)
My advice is, besides being aware and educated about modern fuel and sources, you cant always get the best quality so you should focus in on the very best ignition system you can have (optimize) as well as state of tune and condition of carb, plugs, wires, timing and how you ride.
While many classic bike owners want to stick with originality, And seems most on this list fall into that category, you should consider and value do you want a show bike or display only machine or do you want to ride the bike and enjoy the character of the machine? In which case we start on the slippery slope of what mods are acceptable? Electronic ignitions, Different carbs, or????
Best of luck in your endeavors..
