Race Gas Q's???


12 replies to this topic
  • jclaus98

Posted October 22, 2007 - 06:01 PM

#1

Hey guys, a little help, and this may be in the wrong forum, so feel free to re-direct me to the right one if you know where this should be, but I've got an xr600, so this is where I'll start! I've got two races coming up, the 49er next weekend and then the Prairie City HS the following weekend. What I'm wondering is, if I get some race gas for the races, how do I adjust the carb for it? I used it once before and didn't change anything with the carb and it ran like CRAP!!! Then I read somewhere on here, but couldn't dig it, up that the carb needs to be set differently to accomodate it, any suggestions? Do I need to jet it differently, or can I just lean/richen the mix? Also, is it worth the $6/gallon for a power increase? Any help you guy scould give would be great. Thanks.

  • scalejockey

Posted October 22, 2007 - 07:04 PM

#2

Race gas is only good if your running a hi comp piston.It will not ..REPEAT NOT help at all on a stock motor.even if it's rejetted.
well... Unless your running a mid 1970s' air cooled two stroke on a hilly sand track.

  • jclaus98

Posted October 22, 2007 - 07:44 PM

#3

Perfect, thank you very much.

  • 317

Posted October 23, 2007 - 06:40 AM

#4

It will not ..REPEAT NOT help at all on a stock motor.even if it's rejetted...

If it's oxygenated it will make more power (for obvious reasons).

If the distillation curve appropriately matches the engine's requirements it will make more power.

The term 'race gas' is about as generic as you can get, so you often end up with blanket statements about how it works and why.

  • cleonard

Posted October 23, 2007 - 10:13 AM

#5

For the most part it's not going to help you unless your engine is modified to the point that the extra octane is required.

The term "race gas" covers a lot of ground. Some is almost identical to pump gas, just with some more octane. Some of it is a lot different. When you used it before and your bike ran poorly, it was likely race gas that has a higher density. This is due to aromatics used to get the high octane rating. Higher density fuel makes the mixture richer.

It's funny how with race gas oxygenated is a positive attribute. When it is pump gas it is a negative. As far as I can tell more or less the same oxygenating chemicals are used in both.

If your bikes runs right with pump premium there isn't a huge reason to run race gas. If your engine gets really hot and it starts to ping the higher octane could help. Of course it could help you to just keep hammering on it to the point where you get a real heat related failure. Some of the oxygenated race gas does claim to give a few % more power, but it's not going to be a whole lot more no matter what. We are talking 2% or something.

  • Denn10

Posted October 23, 2007 - 10:28 AM

#6

maybe if your into trying stuff yourself to see exactly if it helps any then try a gallon and mix with some pump gas like 25/75% . Thats what ive done so im not running straight race fuel for no reason. I mix at most 20-25% only anymore just to help a little for cooling and make sure if i got some bad pump gas i dont have to worry about pinging or some other stuff that happens when you get a tank full of crap. If you only buying 1 gal to fill your gas can your only spending a few bucks extra. Just an idea.

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  • jclaus98

Posted October 23, 2007 - 04:03 PM

#7

Just to clarify, it would be Sunco 100 octane, a local 76 station here in sac sells it from one of the pumps. It's like $6.10 a gallon and like I said, I tried it once before, completely drained the tank of the 91 octane and filled the tank with the 100 octane. The only reason that I asked about it was because I had seen something here about needing to adjust the carb for race gas. But, it makes sense that it I would need to be running a higher comp. ratio in order to reap any benefits. But I am interested in what "Faded" said and how I might go about procuring some "oxygenated" fuel? My engine is bone stock, nothing more than an FMF pipe, opened up air box and a UNI filter, so would oxygenated fuel help at all and if so, where do I get some? Thanks for the help guys.

  • scalejockey

Posted October 23, 2007 - 07:34 PM

#8

years ago we got it at the airport. It was purple ave. gas but we also had to jet the bikes way up.

  • Denn10

Posted October 24, 2007 - 11:09 AM

#9

i dont think you would feel that much with oxygenated fuel that you would be willing to keep spending the $$$$ that it cost over pump 91 octane or such.

  • DGXR

Posted October 24, 2007 - 11:40 AM

#10

Your XR600 would probably run best on 91 octane pump gas. I'm pretty sure aviation gas is much different from race gas. But If you decide to run race gas, I think you would need to lean out the carb but that's just a guess. My 1984 XR500R runs awesome on 91 with 2 oz Lucas Fuel treatment and 2 oz Marvel Mystery oil (per 5 gallons) - I put that extra stuff in for good measure, it surely couldn't hurt and the same plug has not fouled in 3 years. Good luck in the races.

  • 317

Posted October 25, 2007 - 05:08 AM

#11

For the most part it's not going to help you unless your engine is modified to the point that the extra octane is required.

If you can't tune for it then yea, for the most part it's not going to help.


It's funny how with race gas oxygenated is a positive attribute. When it is pump gas it is a negative. As far as I can tell more or less the same oxygenating chemicals are used in both.

When you jump in the truck to go riding you're usually wanting the best mileage possible. Since oxygenated gas requires a richer mixture using it sends your mileage down the toilet. When you get to your favorite riding spot and unload your bike most are looking for big power and not how far this tank of gas will get them.


...and how I might go about procuring some "oxygenated" fuel?

Check to see what 'race gas' is available locally and look up the specs to see which are oxygenated and which are not.


years ago we got it at the airport. It was purple ave. gas but we also had to jet the bikes way up.

You can still get Avgas (100LL) at the airport but it's not oxygenated. It does carry an octane rating considerably higher than pump gas (approx. 102 octane R+M/2) mostly due to its lead content. It is also relatively affordable when compared to other 'race' gas. In all my experiences with Avgas (100LL) I've used leaner jetting.


i dont think you would feel that much with oxygenated fuel that you would be willing to keep spending the $$$$ that it cost over pump 91 octane or such.

Then you haven't used it. A 2-3+ hp gain across the board from switching gas might not be worth it to everyone, but if you can't feel it then it might be time to see a doctor.


I'm pretty sure aviation gas is much different from race gas. But If you decide to run race gas, I think you would need to lean out the carb but that's just a guess...

Avgas (100LL) is almost identical to some 'race gas' I've seen advertised. It is also sometimes used as a base for other 'race gas' blends. Other 'race gas' differs enough that the change could be considered drastic. Your jetting will vary based on the fuel, terrain, rider, etc. so saying that all race gas needs leaner jetting is making an assumption that could cost someone some parts.


There are just way too many generalizations, assumptions and misinformation regarding such a broad topic that it's hard to discuss unless you have a specific 'race gas' that you want to talk about.

  • hondacrf150f1

Posted October 26, 2007 - 12:11 PM

#12

just curious? whats compression on the 600R? I run 87 octane my 650R stock motor with uncorking mods, they suggest 93 but it runs great on regular. I tried a tank of Super (93) from a place that had its own pump but the bike ran like crap, like there was water mixxed in.

I know of a local place that sells 105 and 110 octane for $5-$6 a gallon, if i did the 11:1 comp piston could i run this gas? also would it run on pump gas? 87-89-91-93?

  • Denn10

Posted October 26, 2007 - 12:52 PM

#13

if you cant tell a bit of difference between 87 and 91 pump and it doesnt ping then id stay with it, as far as hi comp your gonna have to at least use 91 pump and maybe mix 25/75 or so race/pump. You just have to try the fuels and see how your bike likes it for how its tuned and your weather.





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