Leaded Fuel

[grasshopper]

What is the benefit or not about running leaded fuel? What does the lead do to the motor? Does it hurt or help a modern motorcycle injected or caburated? Why did older cars back in the day run leaded fuel?

[EX_#76]

Leaded fuel provides some lubrication for the valve guides, and it colors the spark plug & exhaust pipe way better for reading the effects of your jetting.  

Modern cars and motorcycles have harder valves, valve guides, and seats that do not require the lead for lube.

The draw back it the lead deposits can build up in the combustion chambers and valves (even on a race vehicle).  These deposits can cause pre ignition problems.  When Ed rebuilt his CB1 the build up on
the back of the exhaust valves was shocking!!!  I think the valve weight just about doubled.    

Guy

[HAWK]

Really no benefit to modern engines but in a race enviroment the lead deposits can actually become conductive (at about 1100 degrees F) and short your spark plugs. No spark-no go.

[Super Dave]

AMA factory road race teams and private teams use leaded racing fuels rather than unleaded racing fuels because they produce more uniform burn which allows for a more complete burn of the air fuel mixture.  

FIM limited power by requiring unleaded fuel.

Leaded racing fuels have different amounts of lead depending upon how it is designed by a manufacturer.  Some use lead to increase octane, while others use it to produce the more uniform flame burn while using other things to increase octane.  

I've used leaded racing fuels for years with no huge deposits of lead.  But, your mileage may vary.

[tug296]

I used to use leaded fuel way back, it burned much cooler in air cooled engines.