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Racing Fuel for CRF

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Curious what you guys think about running fully leaded racing fuels in these 4 stroke engines. Good or bad wondering peoples thoughts. Right now I run high octane no ethanol fuel with marine stabil in it.

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Curious what you guys think about running fully leaded racing fuels in these 4 stroke engines. Good or bad wondering peoples thoughts. Right now I run high octane no ethanol fuel with marine stabil in it.

Once you have enough compression to justify it, yes. No benefit at 9.4:1 compression.

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Once you have enough compression to justify it, yes. No benefit at 9.4:1 compression.

And to add to that, possibility of knock. I'd steer clear of it until you've got an engine to justify it (and the tremendous expense)

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As theraymondguy said, there is no benefit from running race fuel in a low compression engine, it won't hurt it but the leaded fuel will eventually foul the plug. You will not get engine knock [detonation] from running leaded racing fuel, detonation is from running low octane fuel in a high compression engine, not the other way around.

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As theraymondguy said, there is no benefit from running race fuel in a low compression engine, it won't hurt it but the leaded fuel will eventually foul the plug. You will not get engine knock [detonation] from running leaded racing fuel, detonation is from running low octane fuel in a high compression engine, not the other way around.

Racer is partially correct, yes - not detonation - potentially pre-ignition but not detonation (knock) - sorry, I was off my game there.

However, you will not foul spark plugs due to running lead based fuel - leaded fuels actually REDUCED spark plug fouling - especially in engines that tend to run rich.

Edited by theraymondguy

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Racer is partially correct, yes - not detonation - potentially pre-ignition but not detonation (knock) - sorry, I was off my game there.

However, you will not foul spark plugs due to running lead based fuel - leaded fuels actually REDUCED spark plug fouling - especially in engines that tend to run rich.

Guess we will have to agree to disagree on this one lol! I've raced professionally for over 20years [both motorcycles and cars] and have also been making my living by building race engines for almost as long, trust me, leaded fuel fouls plugs.

Pre-ignition is when the fuel ignites before the spark plug fires. This is usually caused by hot spots within the cylinder. Higher octane fuel will usually solve the problem not cause it.

Edited by Racer

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Guess we will have to agree to disagree on this one lol! I've raced professionally for over 20years [both motorcycles and cars] and have been making my living by building race engines for almost as long, trust me, leaded fuel fouls plugs.

Pre-ignition is when the fuel ignites before the spark plug fires. This is usually caused by hot spots within the cylinder. Higher octane fuel will usually solve the problem not cause it.

Sure.

Edited by theraymondguy

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