840 check engine flashing only on the trail

[440dart]

My buds 840 is haveing problems, check engine light will flash after about 10mi down the trail and constantly flashes until you shut it off. When the light comes on it runs great until you go past half throttle. Soon as we get off trail and i shut it off fire it back up it runs really good all day long playin in the trees but get back on the trail 10mi later and the lights back on. any ideas? damn this sled runs we put my holz suspension and 174 in it and its damn near unstopable got the clutchs just about perfect pulling 41-45mph track speed.

 

[Wayniac]

Mine did the same thing on the trail. It was the detonation warning derating the engine. I run a couple gallons of av gas per tank and problem solved.

 

[440dart]

I found that out thanks for the reply did you notice any increase in power? not sure if it will advance timing with racefuel

 

[Wayniac]

With only 2 gallons per tank of 100LL I didn't notice any power increase but it did seem to be running smoother. I have an SLP stage 4 so it probably needed a little better fuel anyways.