Honda-SOHC

Totally agree with you.

Our government here in Canada has made it almost impossible to acquire gasoline without ethanol. Even Shell V-Power now has up to 5% ethanol. Some marinas as well as some airport fuel suppliers offer ethanol free petrol which I have yet to source.

According to our new Google AI friend,

AI Overview,
Yes, the 1972 Honda CB500 Four was designed to run on unleaded fuel, as Honda's engines from the late 1960s onward, including the CB500, featured hardened valve seats that did not require the cushioning effect of leaded fuel. This design foresight allowed them to transition to unleaded gasoline, which was becoming the standard at the time.

Why the CB500 Four was designed for unleaded fuel:
Hardened Valve Seats:
The engines of the time, including the CB500 Four, were built with aluminum cylinder heads and steel valve seats, which eliminated the need for the lead additive for engine protection.
Honda's Foresight:
Honda anticipated the widespread availability of unleaded fuel and designed their engines accordingly, effectively future-proofing their models.

Honda's Foresight:
Honda anticipated the widespread availability of unleaded fuel and designed their engines accordingly, effectively future-proofing their models.
No Need for Octane Boost:
The lead in older fuels was not only for valve lubrication but also for octane rating. However, the CB500 Four had a compression ratio that was well-suited for regular, unleaded gasoline.
Key takeaway: You can safely run your 1972 CB500 Four on regular, unleaded gasoline without needing special additives or concerns about the engine.

Ethanol concerns: The bigger issue for vintage bikes today is the ethanol content in modern fuel, which can cause problems for older fuel system components.
Ethanol can degrade rubber and plastic components found in older motorcycles, like fuel lines and carburetor seals.

It can also attract and absorb water, which leads to rust in the gas tank and corrosion in the fuel system.
If the bike sits for a while, ethanol can separate from the gasoline and cause gummy deposits that clog the carburetors.

Best practices: Many classic motorcycle owners prefer to use ethanol-free fuel whenever possible. If ethanol-free gas isn't available, using a fuel stabilizer is recommended, especially for long-term storage.
How about I help you find some ethanol-free gas stations in your area, or put together a list of recommended fuel additives for vintage motorcycles?

https://vintagecb750.com/?variation=B&utm_source=Klaviyo&utm_medium=email&utm_campaign=Email+%231+Test+%231+July+23%2C+2025+Variation+B&_kx=ttKrgrLBy2l0DgJ9flsF3OZvGOAt8ioQIaOf5ILUfCI.SGgKVC

He seems to have lots of stuff in good and bad looking condition.
https://gentlemansagreementusedvintage.godaddysites.com/

The seal can be done without splitting the cases. Just have to lube it up with grease and with a proper drift, knock it in. The chamfer on the case allows it to go in without too much trouble and without ripping the lip off.

Open up the handle bar switch by undoing the 2 screws. From the inside you can access the contacts. Probably have to loosen up the cable lock nuts as one interferes with the screw removal.

All fast drying spray cans are lacquer based. They have a high amount of lacquer thinner in them. In order to do multiple coats and multiple colors, they need to be sprayed within an hour or so or you'll get the dreaded wrinkling effect. These paints are not gasoline resistant. The high lacquer content is used to slightly dissolve the 1st coat for 2nd coat adherence. If you wait too long, like a day, you will get the wrinkle effect.

There are enamel paints which are oil based and can take up to a day or 2 to dry enough for a second coat or second color. They are more gasoline resistant but color choices are limited. These paints do not wrinkle because they don't have the same solvents in them.

The best paints would be automotive paint and a HVLP paint sprayer setup. Unfortunately, most people don't have this. I used to paint with lacquers and then finalize my paint with several coats of clear lacquer to resist gasoline spills. It worked to a certain degree if you wiped it off immediately. But now that I've gotten used to spraying automotive paints, urethane based, it's really the best and most durable way.

What you could do is paint either lacquer or enamel with spray cans, and organize with an automotive paint shop to finalize your paint job with a urethane clear coat. It won't react with either. You may have to lightly wet sand your paint job with 600 grit just to give something for the urethane clear coat to adhere to.

I am not a paint guru but I have lacquer painted a lot of motorcycles in the past like 40 years ago and just restarted painting motorcycles after teaching myself how to paint cars.