When my 351 grenaded and I did a complete rebuild, I cc'd my head and checked the static c/r of my 351.
If I remember correctly, it was around 12.5:1.
Because of that, I find that anything less than 89 will give me some pinging.
I run 93.

 

Yeah, I can see the 351 being more prone to detonation than the 250 since it has a bigger piston and more compression. I think the 250's and 300's are 11:1 if I remember correctly.

 

My KLR650 had been rejetted using the KLX jet kit from Eagle Mike. When the air temperature goes over 110 degrees more octane makes a positive difference. I live in Phoenix and this time of year highs over 110 are normal.

 

Same as I experienced with the KLX both with the stock piston and the big bore Vulcan piston. Big area having to dissipate heat. Bot ran fine on 87 in the cool months, but would detonate when temps pushed over around 70-75° F calling for at least 91 and usually I just did 93 or 92, whichever. In the winter I'd go back to 87 for the easier firing in cold. I'd actually have to block off one radiator (it had one each side).

Just goes to show a rider has to learn about octane, then listen and think, then do.

 

Yeah mine's blue. And I've used regular. Bone stock KLX250 EFI 2018 model. I just clicked over 3700 miles on it too. I guess the only way to get rid of it (or to make it run less rich) is with an aftermarket EFI unit.

 

Stock these EFI bikes run lean, not rich. Also lean condition increases cylinder temps so it makes sense that the exhaust pipe gets so hot. I have blue and purple on mine too, stock everything.

 

For the extra $1 per fillup I always use Premium.

 

Got it. Thanks. Glad to know it's not only me. For the foreseeable future I don't plan on doing any mods with mine, hopefully it'll be ok.

 

So...you're a money bags braggart...LOL!

 

Mine doesn't ping and I don't lose any power so I save that buck and buy use it for a cup of coffee and a donut.