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Mountain Runner Flash -- Dumb Question; Octane


I have the Shoodaben Mountain Runner ECU -- recently 90-octane non-ethanol  gas has become reasonably available in my area; can I use this all the time, or is the 89-octane ONLY "for the times you are on a long trip and can't get premium octane fuel..."

I've been running 93 octane 100% of the time and am wonderfully pleased with this ECU, but just noticed the new fuel availability -- riding style (if you can call it that...) is to rely much more on the low-mid-range torque than top end power -- my bike sees much more time in the 3-5K RPM range, than anywhere above 8K RPM



This is off of his website,

"10) I tune with 10% ethanol pump gas. Mountain Runner is built with, and can safely run 89 octane. Mountain Runner PREMIUM and THE HAMMER must use 91+ octane, unless throttle is limited to less than 50%."

So, I take that you can run with 89 under all conditions with Mountain Runner.

I have several stations around me that only sell 89 locally, and 91 is the highest premium I can get.  The station that sells 91 shares the hose with the 87 octane, so I figure when I fill up there I get about .8 gallon of 87 from what is in the hose (that is what I have read anyway) before the 91 comes through, so that is something to be aware of as well.

I run the mountain runner flash.  It is a nice improvement in the throttle response.

KC 61

Mini Bike
Pretty sure the owners manual calls for 90+ so that's what I would use. You didn't change the compression ratio with the tune so go by the Owners manual would be my recommendation. I run 91  non ethanol from BP with Ivan's flash and a V&H Slip On and the bike is amazing.


I just messaged with Steve yesterday since I am having my flash upgraded from the EVO to Mountain Runner 89. I only can depend on getting 91 octane consistantly in my area and that will work with the Mountain Runner 89. The Mountain Runner Premium requires 92 octane and above unless like stated above, it is held to below 50% throttle. I went with the MR 89 since I didn't want to chance it with the wrong fuel and have problems. If I had better gas in my area I for sure would have gone to the MR Premium flash. My ECU is in the mail to him now so hoping I like it better than my EVO which is great.


MOB beat me to it, but I agree with him. {please don't tell anyone I sed that  :truce:}

If your worried about octane values, keep a little octane booster with you.
  Problem solved.

Dirtwiz, with that info, ya might want to consider the Mountain Runner Premium? {Hint hint}

Ride safe, Ted