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Mitch_from_Oz

Leaded Fuel????

4 posts in this topic

Hey Guys,

I have been told by persons who appear to be in the know that leaded fuel is good for the YZ?WR400's.... Has anybody else heard of this?????

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There are 2 'myths' associated with leaded fuel. 1. Leaded fuel will let your bike make more horsepower. 2. Leaded fuel protects your valve seating surfaces. First: lead as a gas additive will raise the octane of an existing mix, but unless your bike is pinging on the gas you are using, more octane doesn't make more power. Second: Engines that were manufactured with valve seats made out of soft materials like a 1964 Harley Davidson or Triumph would slowly have their valve seats eaten away by unleaded fuel. But even the 1969 Honda CB750 had valve seats made out of Stellite or an equivalent hard material that can tolerate unleaded gas (there are still a zillion of them running). Modern bikes were designed to run on unleaded fuel by smart engineers who are not going to put cheap materials in the wrong places, I mean they've got titanium valves!! It's probably going to take another 20 years for that myth to die. Lead was banned by the government over health concerns from both gasoline and paint.

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I've read in magazines that lead can help the exhaust valves run cooler and is helpful when exposed to prolonged high rpm use. Leaded fuel is still available as race gas from some sources and aviation gas still has lots of lead in it. NASCAR and small piston driven aircraft are the biggest users of leaded gas these days. I've heard it's best not to use straight av-gas because its formulation is optimized for use at a continuous throttle setting. Also, lead substitute is available from some auto parts stores. I figured a little lead substitute can't hurt since my valves were approaching the point of needing new shims. Since I started using the substitute, the clearance hasn't decreased to the point where new shims are required.

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I have to agree 100% with Debarker. Lead isn't the way to go. I may add that the lead may actually build up similar to unused fuel (carbon) on the valves and seats, thus potentially causing more damage than good. Race cars and airplane engines are rebuilt quite often, so any damage is taken care of. It may even prevent the valves from fully seating closed as does carbon buildup (maybe this is why Jeff's clearances haven't changed?). This would lower the compression and make the engine more sluggish. I am sure it would take many, many miles for this to happen, but when it comes to out precious WR's, better safe than sorry.

Another reason, albeit tree-hugging is the damage to the environment-especially your friends riding behind you! Lead kills!

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