Opinions on running aviation fuel

[Pacheco_450r]

My 450r will boil over once in a while when im pushing it real hard at the dunes or track on 91. Sometimes ill mix some vp110 in to help prevent that since my compression is right on the edge of needing more than 91. My local airport sells 100 octane leaded av gas for $5/ gal at a pump, some guys swear by it in their bikes. Last can of vp110 I bought was $65 ....that's $13/gal! I have a cousin that runs av gas in his jeep (built 350 no cat, sand toy) and said the only time it's caused him a problem was when he ran it straight his carb would stick once in a while, but never had a problem when mixing it. I wonder if that is due to the high lead content, or if it's a common problem running in a smaller carb like a quad vs a carb on a v8?

[chris p.]

$5 a gallon for 100 ?? it's not cheap but that's cheap !! i'm in Connecticut and 100 varies from $9 to over $13 at the pump. I run it straight with amsoil dominator 2 stroke mix and I've never had a problem. we've had a built drr90 and countless dirtbikes. I also run it straight in my 70 Camaro with a built big block with no problems.

[CJM]

All my buddy uses in his built 450, no issues.

I run 92 and havent ever had mine boil over and I ride dune/desert around here. I have had the fan kick on alot though during low speed playing or riding around. I have a similar setup to you Pacheco, 04, 12:1, hotcam stage 2, ported head and exhaust.

[Pacheco_450r]

All my buddy uses in his built 450, no issues.

I run 92 and havent ever had mine boil over and I ride dune/desert around here. I have had the fan kick on alot though during low speed playing or riding around. I have a similar setup to you Pacheco, 04, 12:1, hotcam stage 2, ported head and exhaust.

Im glad to hear no problems from av gas so far.

Ya CJM I put the 12:1 in it hoping it would be fine on pump gas. It usually is other than like you said, where im dragging the clutch a lot on tight tracks. My fan kicks on too but ill still get a little coolant splashing out over time. Ive had the radiator cap pressure checked, and the thermostat is also fine.

My motor guy reccomended to mix some race fuel in just to be on the safe side, and that does stop it from boiling over, but I still find it strange. Especially that theres no other work done on it like a cam or head work.

[CJM]

Honestly Id say I might have slight boil over myself sometimes. I know I filled up the coolant tank literally 100% full but when I flip the quad up to powerwash it I sometimes notice spilled coolant around the tank that must have come out from the stem. The overflow tank is also about 1/4 cup low too. Then again I wonder if its just b/c I overfilled the tank and it has nowhere to go?

[honda250xrider]

I used to run av gas years ago when it was easy to get. Worked fine for me for several years racing using 13.5 compression.

I have a pump by me that sells turbo blue; it's the same price and less headache for me to get which is why I don't even bother trying with av anymore. I wouldn't hesitate to use it again if I didn't have race gas nearby or had to pay $13 a gallon for some.

Locally around here I believe it was hovering around $6 for av and turbo blue was $6.50

[chris p.]

Pacheco : if you're boiling over have you looked into the cooling system ?? pinched/blocked hose or radiator problems? are you running antifreeze or a mix ?? we used to use coolinol fluid and never had a problem. could you be detonating and not realize it ?? do a plug check and see what the porcelain looks like. usually if you use the better fuel that would stop the death rattle and keep it running cooler hence the stoppage of the heat problems although the better octane doesn't add power: it won't detonate as easily allowing you to add more timing thus making more power.

[Pacheco_450r]

Pacheco : if you're boiling over have you looked into the cooling system ?? pinched/blocked hose or radiator problems? are you running antifreeze or a mix ?? we used to use coolinol fluid and never had a problem. could you be detonating and not realize it ?? do a plug check and see what the porcelain looks like. usually if you use the better fuel that would stop the death rattle and keep it running cooler hence the stoppage of the heat problems although the better octane doesn't add power: it won't detonate as easily allowing you to add more timing thus making more power.

Yes I've checked the cooling system and everything is good, I run lp racing coolant (orange) and add amsoil dominator coolant additive but it still runs on the hot side sometimes. I've never heard it knock and the the plug looks good, I just think for some reason I'm right on the edge of the limit for compression. It's definitely getting plenty of fuel, I run a 190 main jet and it's spot on.

Av fuel is easy to get at my local airport, literally pull up to the pump swipe your card and punch in how many gallons you want. Much better deal than race gas that I have to drive half an hour for at the nearest shop.

[chris p.]

hmmmm how about a bigger radiator ??

[Pacheco_450r]

hmmmm how about a bigger radiator ??

Its on my parts list when I do my teardown and rebuild

[450rtt]

I run 100LL avgas in all of my motors. People think i'm crazy for putting it in my lawn mowers and string trimmer/chainsaws. I like the smell. I run it in my built 450 and my built 400ex. The 450 is a 13.5:1 ratio and it does just fine on the 100LL. The lead is an added benefit as well as no ethanol! Cheap alternative to pricey race fuels.

The only negative claims you will hear about avgas is that it's made for high elevation and is designed to be stable with less oxygen. This is not true. Avgas is not jetfuel, it is not designed for planes that go 30,000 ft in the air, it's made for small aircraft, crop dusters, ultra lights, cessna's, planes like that. My local airport hooks me up with the fuel at $5.50 a gallon and i've talked with the fella several times about the fuel and he knows plenty about it. If you think about it, when does an aircraft need max power? On the ground, during take-off.....if this fuel was truly designed for high altitudes that would hamper the performance during take off. The fuel is just fine for our motors and in my experience, they like it!

[blaster99]

I ran AV Gas for years in my lower compression but still built engines. I never had a problem, but I've heard the high altitude story, along with the fuel is only made to be run at a constant lower RPM. I wouldn't worry about it, if I ever end up with a quad again, I would use AV Gas if pump isn't suitable.