i know iv seen this here before a time or 2, but i had a question. what would be better to run, av gas or premium pump? im not too interested in running it right now, but whenever i get a new bike (kinda gettin ahead of myself)

is it not good to run it on a bike with stock compression? or does it matter?

On stock compression, run pump gas. That is what the bike is designed for, so it should run best on that.

so say for ex, i were to bore 40 over, like a 440, and comp was 11 to 1, still pump or av/race? if its 12 or nore then rae, correct....


24v what do you run?

people run av gas all the time, mostly for some reason other then actual need. Why would you need to run it?
higher compression on the piston=you did some motor mods
all other reasons should only be valid and needed if the bike is running hot or pinging....in which case a bleand of av and pump would work..
some guys run it because they like burning $5-8 a gallon fuel....

av gas is aviation fuel is was designed to run at high altitudes and at a constant rpm. also it runs dryer than pump/race gas so it will run your engine lean. unless you do some major engine mods I'd stick with pump gas .

I got this from one of Robbie's posts.


Racing Gasolines - By 76 Products Company

I am going to attempt to address the controversy of aviation gasoline verses racing gasoline for use in race cars. Some racers use aviation gasoline, which is fine for some applications but does have shortcomings. There are several grades of aviation gasoline (avgas) that we must identify before going any farther.

1. Avgas 80/87: this product is used in low compression ratio aircraft engines, contains little or no lead, is red in color, and should not be used in any automotive engine due to a low motor octane number of about 80.

2. Avgas1000/130: this product can be used in some automotive engines. It has both research and motor octane numbers slightly over 100. Avgas 100/ 130 is green in color, contains four grams of lead per gallon, and is becoming harder to find.

3.Avgas 100 LL: the LL stands for "low-lead" which means two grams per gallon, low compared to the avgas 100/130 that it was designed to replace. It has research and motor octane numbers very similar to the 100/130 product previously discussed. The color is blue. This product sometimes has a high level of aromatics which can contribute to lazy throttle response and dissatisfaction of the consumer.

4.Avgas II 5/145: this product was developed for high performance piston aircraft engines used in world war II and in the Korean war. It is very hard to find anymore due to lack of demand although it is of very high octane quality. The color is purple.

The remainder of this discussion will assume that our basis for comparison with racing gasoline is avgas 100/130 and/or 100 LL since they are both available and have acceptable octane quality for limited applications. When the word "avgas" is used, it will refer to avgas 100/130 or 100 LL.

Avgas is less dense than most racing gasoline. Instead of weighing about 6.1 to 6.3 pounds per gallon like racing gasoline, it weighs 5.8 to 5.9 pounds per gallon. The racer must compensate for this by changing to richer (larger) jets in the carburetor when changing from racing gasoline to avgas.

The other major difference is octane quality. Avgas is short on octane compared to most racing gasoline. Many racing engines with "quick" spark advance curves or with no centrifugal advance have more spark advance at low rpm than avgas and some racing gasoline can handle. The result is detonation, especially during caution periods in circle track racing because all of the spark advance is "in", rpm is low, and part throttle air fuelratios are too lean for the operating conditions. If the driver does not "work" the throttle back and forth, pistons can be "burned" which melts away part of the aluminum piston material. Inadequate octane quality is one of the quickest ways to destroy an engine. Pistons can be severely damaged during one acceleration where detonation is present and the racer may not know what is happening until it is too late.

For maximum performance and power from a racing engine, racing gasoline will normally provide better performance than avgas. Avgas can be a good gasoline for some applications, but since most racers do not know the octane requirement of their engines, they would be better off with a "real" racing gasoline that will give them the overall resistance to detonation that they need to protect their investment. If someone has spent from $15,000 to $50,000 or more on their racing engine, it is foolish to cut corners on gasoline be sure you have a gasoline with adequate octane quality.

I've been running Avgas for quite some time, mainly in my older ATC's, which were built when "regular" gas was prevalent on the market (with lead in it). My main reason for running it is, that here in Phoenix, the pump gas is so polluted with emissions-reducing garbage, that it has a 2-3 WEEK shelf life, as compared to the 2-3 year shelf life of avgas. In short, my bikes can sit all summer and not have plugged up jets, etc. I really don't need the performance increase (if there is one), I just like not screwing with my bikes every time they sit for awhile. I should say that I've been considering doing some swapping back and forth during the season, maybe a diluted avgas mixture, especially toward the end of the season...

Also AV gas is 100 octane and only about $2.75 a gallon ATM. I go back and forth between 91 and Av gas. No real difference in either so I have been just running 91. My compression is 12.1.

You don't really need more octane than 91 till you get to 12.5 IMO.

av gas is fine to use, just add a little 2 stroke oil to it to add some lubricity. also if you set your jetting to the fuel you use you will be fine, but dont expect the bike to run good on av gas when its jetted for arco 91 octane. one benitfet of runnning av gas is that the fuel will be the same every time usually, not the case with pump gas, even at the same station you could get different gas weeks apart as the shelf life of pump gas isnt very long at all.

I heard just the opposite as painterjoe. Not sure which is correct. I've heard av gas is set up for the most critical part of the flight. Take off and landing which isn't high altitude. Thats just what I've heard. My dad used to run it in his vw buggy. We'd sneak over to gillespie field and buy it. We had the combo to the gate.

hay mike run synthetic oil in your 400ex and one way to find out if its jetted rite iss do a plug chop

i dont remember what kind of oil im running. hey eric, wanna jet my bike? ill give you a dolla....

G1500 no reason to run anything other than 87 Octane in your quad till you up your compression. The reason the engine runs cooler with higher octane gas is due to incomplete burning of the gas. Making for an inefficient engine.

mi engine gets hotter than a motha, is that good?

I would be willing to be it is not jetted properly. Find someone with similiar mods on the same bike, and see what they are jetted at. then pull yours out and see what they are. Jetting is easy. The jets all have the numbers stamped on them. The higher the number, the richer the jet.

I ran av gas in my jet boat before because of the compression 11-1(did so for years no probs).On my bikes i ran 91 because they were stock gsxr 750(street bike) 12-1 comp premium recomended.On my 250r when stock 91 in it now that i raised the comp i need to run 50/50 of 110 and 91.I am sure i can use straight av gas but i really dont know how 2 strokes will react to it and race gas is easier to get for me.IMO if they are stock motors wheter car,boat,trucks,bikes.stick with pump gas

well here goes my 2cents,i use to run avgas in my r and it ran great no problems ever,but of course u mix it with oil which avgas is a VERY dry fuel.and onthe other hand i ran it in my z400 a few times straight and BAM it burned a hole in my silencer spark arrestor screen so who knows what it did internally i sold it. so personally i woulnt do it again on a stock bike but if u feel u have to use avgas on a 4stroke b sure for one run a 30/70 blend 30av-70 pump gas.or drop a few ounces per 5 gallons of Marvels myster oil.

unless your up over 12.1 , race gas is not needed, and is a waste of HP and money.

............Using a higher octane then necessary is not only a waste of cash but can cause build up deposits that your engine can't burn. Which will lead to needed to run this octane to keep it from dieseling (running after shutting off the ignition)in the first place. (Deposits form causing hot spots, and pre-igniting the fuel before the Spark plug is suppose to.)Called detonation or pinging.

Remember Higher octane gas actually burns SLOWER or cooler then lower octane fuels. Using this will cause the fuel that is not being burned to build up in your heads,valves,pistons, etc...... So the trick is not what you think is best,but actually matching the octane to what your timing, ignition, and engine can actually burn in the compression stroke.



most guys run VP or unocal because of the availability.

most race guys pushing 13.5 to 14.1 + use nutec
NUTEC