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Discussion Starter · #1 ·
Just noticed the closed thread on running leaded fuel.

Nothing to add to any of the comments about octane ratings, but be aware that running any leaded fuel in engines designed for unleaded petrol will result in lead fouling of the valve seats.

If you use a leaded fuel you'll probably need to regrind the valves fairly frequently.

Rob
 

· Ninja Bike Forum Mod
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Just noticed the closed thread on running leaded fuel.

Nothing to add to any of the comments about octane ratings, but be aware that running any leaded fuel in engines designed for unleaded petrol will result in lead fouling of the valve seats.

If you use a leaded fuel you'll probably need to regrind the valves fairly frequently.

Rob
It has always been my understanding that running leaded gas does little to no harm to hardened valve seats associated with unleaded engines. Especially since lead is softer than aluminum or steel. But the inverse was true for older engines designed for leaded gas, which helped to bolster the 'soft' valve seats back in the day.

I don't know if it's different in the UK, but that's what I've been told since I was young and working on hot rods.

where in the world can you still buy leaded fuel?!
Race gas in the US is typically leaded, because it's easier to attain higher octane ratings that way.
 

· Powerhungry
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im still running an engine with soft seats, designed for leaded fuel.
its in my offroad truck. when i remember, i use the leaded additive. but ive been told i dont need to do that. im not sure either way.
BUT, ive heard the same as jay, that it wont hurt anything when running hardened seats.
 

· Ninja Bike Forum Mod
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The older engines typically don't have stiff valve springs, or see high RPM loads, which is why it's generally safe to run unleaded in one designed for leaded fuels. But, when you start making more HP it's not bad to have hardened seats installed or upgrade the heads.
 

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Discussion Starter · #7 · (Edited)
It has always been my understanding that running leaded gas does little to no harm to hardened valve seats associated with unleaded engines. Especially since lead is softer than aluminum or steel. But the inverse was true for older engines designed for leaded gas, which helped to bolster the 'soft' valve seats back in the day.

I don't know if it's different in the UK, but that's what I've been told since I was young and working on hot rods.


Race gas in the US is typically leaded, because it's easier to attain higher octane ratings that way.
The lead doesn't actually do any harm, but it tends to build up on the seats, leaving the valves leaking a little, and has to be removed occasionally by re-grinding - or at least that's what the Japanese bike manufacturers used to tell us in the days when leaded and unleaded pumps stood beside each other.

As you say, when petrol used lead to increase the octane rating, manufacturers made use of the fact that it it was there and made use of its lubricating properties in the design of their valve seats.

If you live in an area where emissions are checked as part of an annual inspection and a Catalytic Converter is mandated, lead will of course destroy the converter. So far the EU doesn't check emissions on bikes - at least in the UK.

Rob
 

· Ninja Bike Forum Mod
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They don't check it here either on bikes. And from my reading yesterday it will take some time for it to clog up the converter or leave enough deposits on the valves to make a difference. I should say thanks for making me read up on the subject again, actually. I could only assume that the RPM and heat that these engines produce the deposits can't build up too easily, and that one tank here and there won't cause any issues. I know I used to store my bike with 114 octane leaded race gas as opposed to the blended ethanol (reformulated) fuels at our pumps because it is less likely to turn to varnish when sitting over the winter. And also because of octane degradation while gasoline sits, I figured that a higher octane would keep the fuel in a safe octane range by spring.
 
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