SOHC.co.uk Forums > CB500/550
Lead Replacement Additives for Fuel
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
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