Hey I was wondering if I can run straight race (108) gas in a 400ex with fmf, k&n? Never ran it in a 4 stroke, just wondering if there is anything i need to do. Thanks.

 

I've ran turbo blue, which ran fine, and 117oct fuei mixed 50/50 with premium, which also ran fine. 112 oct was too much though! My 400 had full exhaust, needle raised 1 click(dropped washer down 1) and 152 main jet. I could keep up with z400 until 5th gear, even pulling away little bit until 5th.

 

You can run it with no problems, but you will waste money and actually lose power. You only need to run as high octane as required to keep detonation at bay. Like I said, you can run it no changes to anything except for a loss in performance. The only time you need to run higher octane is with and increase in compression and other physical motor mods.

 

Yep! Ditto NCScrambler!
You're wasting your money unless you have some really high comp.!
Only good for keeping the little detonation man away!

 

All I know is, 4-wheeler ran better with race fuel in it. Higher quality, I would suspect, waste of money, no comparison.

 

Listen to ncscrambler, he is RIGHT!!!!!!!!!1

 

Here are some good articles to read on the subject. Gas Here is a 4 page article on everything you could ever know about gas. Gas FAQ. Hope this helps everybody understand what I am saying that too high octane can rob power.

 

For sure, you are throwing money right out your exhaust pipe. There is no reason to run race gas in a stock compression 400EX.

 

You guys are correct about higher octane fuel can actually rob power and be a total waste of money, but, to say it most definately will rob power and waste money is wrong. I scanned through your links, ncscrambler, and they were informative. It says in your links(gas), it sometimes happens when using a different fuel the engine seems to run better. I'm no mechanic, proffesional racer, or expert on fossil fuels. If you really want to know how it will run, try some. Don't get carried away with it though. My 400 ran great with 105-108oct in it. It was really nite and day, quicker throttle response and more power from bottom to top. I'm friends with a local gas station owner. He informs me about some of the @#$% gas that some stations offer. I wont go into why its @#$%, but a lot of gas, even premium gas, here in the midwest is not what its cracked up to be. Sometimes its good, sometimes not. I didn't use race gas all the time, just when I ran at some local tracks.

 

I will agree that pump gas has it's faults, it is inconsistent, may have water in it, etc. If you will read close to those links it says that some bikes may run better with race gas because it matches their jetting closer. What that means is that your jetting for the grade fuel you are currently running is not as closely matched as it should be. If you want to run racing gas, run a mixture of about 25% in there and you will have a better consistency. I do this and it works great, you are only raising your octane a few points, maybe 97 with 93 and race gas mixed, but it does seem to help and you can also see my atv is not stock either. If you must run race gas, try a mixture first, at least with a stock bike and that way you will gain some consistency. I would not recommend running full race gas though as It will be a waste of money.