a little cheese with your avgas?

[BiggerRed 400ex]

I am a pilot and have easy access to 100LL avgas. I ride a 400ex and have been contemplating using avgas in a 75/25 or 50/50 mix with premium pump gas. I have read other posts on fuels and stuff but I have a relativly stock bike... (no choke, stage 1 rejet with 2 on the way, K&N filter, and stock airbox with outerwears on the way, stock exhaust with e- series on the way) Im a little confused on why a lot of people are downing avgas.... it contains lead with is good for a motor RIGHT:huh ... AND if it does infact burn COOLER isn't this what we want on an air cooled engine? Im not nessisarily interested in BIG gains like i might expect from a racing fuel but more of keeping the engine happy for a long time , sure i still want gains but i dont expect to get it from fuel... Just still doing research and thought you all might have some input from experience....
P.S. i also know that you have to richen the jetting with avgas.
Thanks
Ryan

[big-guy]

The only advantage avgas would have would be a resistance to detonation, because of the higher octane. unless you're running insanely high compression, this is overkill. As for the lead, it's mainly there to lubricate the valves, and this really isn't needed in a modern four stroke engine.
A cooler running engine sounds like it would be a good thing, but believe it or not, an engine will produce more power and run more efficiently at a higher temp. Most modern cars will actually idle at around 230 degrees. The only problem with the higher temperature is that it causes the oil to break down, which is why synthetics and blends exist.

Bottom line, avgas would be a waste of money. If you wanted to run alcohol, for say drag racing, that would be reasonable, but keep in mind it will take quite a bit more fuel to produce the same amount of power as gasoline, due to the differences in latent energy.

For engine longevity I would run pump gas, the lowest octane you can without letting the engine detonate. I usually run premium unleaded in mine.

[skemp]

Avgas is also oxygenated pretty heavily compared to other fuels. The reason for this is that it is meant for airplanes, which are at higher altitudes where oxygen starts to get thin. The oxygen is added to help make the air-fuel mixture closer to what it should be so the motors can make more power.

[Desert Rat]

Good advice from Big-Guy and Skemp. Higher octane does not produce more power. Higher compression, that causes you to need higher octane to keep from pinging, is the power maker. As for Avgas pros and cons you can ask ten people and get ten different answers. I run the 100 octane avgas in high compression VW rails with good results. I run 93 octane pump gas in all my quads that have a little bump in compression (11/1 in my 400ex) with good results. You just don't want them to ping.

What Big-Guy said!

[BiggerRed 400ex]

Ok ... i think i willl stay away from avgas... thanks for all the input.... would lead additive be of any good?
thanks
Ryan

[skemp]

I don't know too much about lead additives... Valves do like their lead, but I wouldn't be too excited about dumping some mysterious concoction into my gas - that's just me. I just stick with the good old leaded race fuel, but I need it. I only have 10.8:1 comp, but it pings with anything less than about a 40/60 mix of 92 pump/110 race fuel.

I ran avgas a few times last year, because my step dad hauls gas and gets it all the time for free, but it would ping when I was putting a very hard load on the motor, like during a hard hillclimb. I switched back to 92 pump, and the ping disappeared.

Seriously, do what you choose, but since you have a stock motor, your best bet as far as price and performance go would be to run a quality premium pump gas. Your wallet will thank you, trust me. :)

[big-guy]

If it was say, a 1955 vw beetle with the original heads, I'd use the lead additive. It offers no advantages to a modern engine though, and would only serve to increase pollution (and lighten your wallet).

just change the oil, and ride the thing.

Big-guy

[Kawboyz beware]

My friend was running Cam2 race fuel 110 octane out of the pump in his 400ex mix 50/50 it ran fine but was a big jump in price. I also use CAM2 in my 70 OLDS w-31 mixed 50/50 and the car never ran so good. The lead Acts like a cushin on the valves to prevent valve recession which will happen in a car with out harden seats that is why lead is needed. Note: not all octane boosters or lead additive contain Lead.. I found Lead Supreme to be the Best .