My bandit likes 98 Octane (or at least > 91)

My bandit hasn’t been running so well lately. On the Narooma run it was breaking down when full throttle was applied fast but OK if you rolled on gradually. Started out just in the lower gears but seemed to progress so that it was happening at high speed in the upper gears.

Then I remembered that it had been screaming at the track day 6 weeks ago, and, for that, I had filled up on 98 as figured I would be hammering it all day and thought the higher octane fuel would give the engine a bit of margin and a clean. So anyway I drained the tank and refilled with 98 and it is screaming again!

I am theorising that with the slip-on, TRE and the K & N filter my bandit is running quite lean and the engine management is detecting this and applying a limiter to prevent detonation… but I am open to better informed opinions.

I am just happy that my bike is running OK again.

Cheers Peter

you are a lot better informed than me!!

I've run 91 in mine no problem, but I do have a power commander and it has been mapped for the bike. If you don't have one I recommend getting one. 91 should not be a problem unless it is from a dodgy servo.

the bandit does not have a knock sensor so ign timing will not be retarded due to pinging.

Things that come to mind as being possible culprits are fuel filter becoming clogged, but that doesn't explain why when you put 98 in the bike it got better, or dodgy fuel (the 91 stuff) perhaps mixed with something it shouldn't be or had water in it.

dhula wrote:the bandit does not have a knock sensor so ign timing will not be retarded due to pinging.

So maybe the O2 sensor sensing a dangerously lean condition? I was also thinking fuel pump as it did have a lot of the hallmarks of fuel starvation, also thinking maybe the TFI is bad...but I would probably expect that to either work OK or be totally rooted in which case a default to the 6th gear map >>> dodgy idle and sidestand cut-out.

I do have a DFI and I will be doing a Holeshot stage 2 before a visit to Eastern Creek mid-Feb and doubtless this will make it run OK on 91, but all idea's are welcome.

if it was me I'd try another tank of 91 non ethanol fuel. Shell sell it and I know of one BP station here that refuse to sell the ethanol stuff. Run the tank near empty or siphon what's in it out and add say half a tank and try again.
Octane doesn't really matter much in this engine as long as it is 91 or higher. In saying that, my "arse dyno" tells me the bike runs better on V-power.
I remember seeing an article years ago (10+) in a Fast Fours mag about making a visual knock alert device using a knock sensor from a car and rigging it up to a light on the dash to aid tuning. There was some basic electronics involved from memory (fast fading).
Pity you cant play with timing like to old days of points ignition.