I have an 06 carbed and it runs better on 89.I tried higher octane and the bike didn't start or idle as well.Higher octane fuel burns slower and produces more carbon in the cylinders.Engines are designed for a specific octane level so use the correct one.Higher comperssion ratios require more octane because of the heat generated on the compression stroke.Take a diesel engine for instance.They have very high compression ratios and the fuel ignites due the temperature in the combustion chamber.They don't need spark plugs because it gets so hot from the compression.That is why high compression gas engines need premium gas.It burns slower and won't auto ignite causing detonation.The flash point of high octane is much higher and the main reason it carbons cylinders.

 

I only use Sunoco ultra 94.I have used 93 octane but only 2 times.I have 18,000 miles and the Sunoco has done me very well

 

I would stay with 93 and maybe 100 every once in awhile running a 100 will burn your vales up if used all of the of the time.

 

The 2008 Sportster Owner's Manual states on page 32 to use 91. That's what I'd recommend using. But who's got a manual for a 2001? What's it recommend?

 

I use 95. I don't think it will do anything to the bike if you use higher octane.

 

92 or better, 108 race fuel when I can find it!!!

 

What he ^^^^ said!!!! Stick with the 89 unless you're getting some pinging.