95 octane in San Diego, CA...?

[bananabender]

My 94 CR250 is retired now and her successor is a 2006 YZ250.
My old lady was happy with 91 pump gas, spiced up with oil! Now, that new YZ wants 95 or better… Do I really need this? I am not racing and go to the track ones in a while, but mostly I go to Ocotillo Wells…

Is there a gas station with high octane fuel here in San Diego? I am used to go to the Chevron on Miramar Road – I think 91 is the best they have…

Octane booster? Crown Royal? Sriracha hot sauce?

 

[Rich Rohrich]

The Yamaha minimum requirement is 95 RON. It's common for US fuel to have a 10 point spread between the RON and MON ratings (called the fuel's sensitivety), so some quick math (R+M) / 2 gives us:

( 95 RON + 85 MON ) / 2 = 90 pump octane or AKI

So essentially any pump premium (93-91) in the US will "technically" satisfy the minimum octane requirement of 95 RON.

Outside of the US the number at the pump is RON, so the numbers are larger but the fuel has the same basic octane rating when compared using the same test methods.

 

[a454elk]

Thanks Rich, I now have a headache. So bottom line, I can still run pump gas too. ;)

 

[bananabender]

Rich, thanks a lot!

 

[Rich Rohrich]

Thanks Rich, I now have a headache. So bottom line, I can still run pump gas too. ;)

Yep. The Japanese don't currently build standard production bikes that won't run on US pump premium. Although some of the new two-strokes are really bordeline.

The only time I've ever seen them actually spec a higher than pump octane fuel is with the two-stroke road race bikes (TD,TZ, RS the serious roadrace stuff).

 

[bananabender]

Perfect - and my new Japanese lady is bone stock!

 

[Studboy]

Most of the 2006 YZ250s do ping slightly on premium pump gas stock.

The culprit: Excessive squishband clearance. My bike measured out at 0.085". I think that most of the new YZ250s are in that range.

The remedy: Bring the squishband into the 0.050" +- 0.005" range.
I achieved this by milling the cylinder head down and removing some material from the dome to keep the stock compression ratio.

The results: No more pinging and better response!