Lead Replacement Additives for Fuel

[Robert W]

I saw a post from way back in 2010 about the need for lead replacement additives in fuel and was wondering if there was any change in opinion that it wasn't necessary. Anybody know if the CB500 1972 K1 engine has hardened valve seats?

[florence]

My understanding is that any Japanese motorcycle built 1974 onwards is fine with lead free petrol; I have been running mine since 1995 unleaded without any problems.

[Bryanj]

I thought that was all honda fours are ok

[florence]

Good point, same engine 1972

[Athame57]

I got told on here about six years ago by Julie I'm sure it was that unleaded was just fine for my CB400F. 

[Nurse Julie]

Hondas were built from about 1965 to run on unleaded fuel. No additive required.

[Robert W]

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?

[Nurse Julie]

Blimey, that's a bloody long winded way of saying what I said originally....... No, you don't need lead replacement. Ethanol isn't an issue either as long as you change carb O rings etc to Viton, which many of us have done for years anyway.

[Robert W]

Julie,

It's not me it's our new best friend, Google AI. Haha

[Bryanj]

Google and intelligence in the same sentence

[deltarider]

It can also attract and absorb water, which leads to rust in the gas tank and corrosion in the fuel system.

Hmm, it is a bit more complicated. Alcohol absorbs water, binds it and so passes the combustion chambers with no problem. In this form it does not cause corrosion in the tank. Actually it is better in this respect than gas without alcohol. Then any water like from condens will sink to the bottom of your tank and possibly cause corrosion.
Thinks go wrong when gas with alcohol is allowed to absorb so much water, like in an only partially filled tank for a long period of time, that it can no longer bind it all and phase separation occurs. That can cause all kinds of nasty problems. 5% of alcohol or less should be no problem, but you can also opt for premium alcoholfree gas like V-power or Ultimate. But these juices are more expensive.

[Robert W]

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.

[deltarider]

[...] Even Shell V-Power now has up to 5% ethanol. [...]

In EU it's law to have '5%' put on the V-power pistol's grip, but in practice the actual percentage is still zero or neglectable. 

[Rayzerman]

Ethanol will saturate at about 4.5% water, then it can't take any more, and excess will separate and sink to the bottom of the tank.  Isopropanol on the other hand can take care of many times that.  So, if your bike is going to sit, dump in some Seafoam, which is naptha (a component of most fuel additives) and ~30% isopropanol.  Or you could use a couple ounces of isopropanol by itself.  The naptha is a slow-acting solvent, dissolves gummy deposits.

The problem with water occurs when you have a partial tank, and not in a stable temperature environment... i.e., the tank breathes as the air expands and contracts, drawing in new moisture.

[deltarider]

Ethanol will saturate at about 4.5% water, then it can't take any more, and excess will separate and sink to the bottom of the tank.  Isopropanol on the other hand can take care of many times that.  So, if your bike is going to sit, dump in some Seafoam, which is naptha (a component of most fuel additives) and ~30% isopropanol.  Or you could use a couple ounces of isopropanol by itself.  The naptha is a slow-acting solvent, dissolves gummy deposits.

The problem with water occurs when you have a partial tank, and not in a stable temperature environment... i.e., the tank breathes as the air expands and contracts, drawing in new moisture.

Yes. It's ironic that fuel system additives - which can be very helpful - consist for a large part of alcohol. Naphtha is also wonderful stuff and is the only petrochemic product that I know which is safe for all rubbers. Problem for me personally: I can't stand the smell. If I use it outdoors I will have the smell in my nose for the rest of the day.
So you could make your own fuel system cleaner. But I don't know how to compose it thus that the brew will evenly mix with gasoline and that's what commercial products claim they do. So... your choice.