gearhead1

Member
Feb 19, 2004
2
0
I haven't been on Bike in years, wanting to get back into it, so I bought a '98 YZ250. I know stuff has changed, so I'm trying to figure out the Octane requirement.

I've tried the following: searches on here, calling Eric Gorr (no answer), called Yamaha, and local dealers. The dealer says my minimum octane requrement is 93. The Clymer repair manual says 95. When I called a fuel supplier (trying to find high octane fuel in my area) he says the number in the book is probably a RON number and I could probably use 93 pump gas which is found by (R+M)/2.

So which is it (assuming no modifications from the factory, bike hasn't been raced that I can tell).

Thanks!
 

elf

Member
Jun 7, 2003
695
0
93 pump gas will work just fine. My brother has a 97 and i had a 2000 both bikes ran great on premium pump gas.
 

Rcannon

~SPONSOR~
Nov 17, 2001
1,886
0
I would love to be able to find 93 at my local pump. The best I can do is 91.

I have had no trouble running this in my 97 YZ 250. Obviously, jetting has to be somewhat correct. I am also running at 4500 ft elevation.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
gearhead1 said:
When I called a fuel supplier (trying to find high octane fuel in my area) he says the number in the book is probably a RON number and I could probably use 93 pump gas which is found by (R+M)/2.

He's correct. :thumb: The usual difference between the RON & MON rating is 8 to 10 points (called the fuel's sensitivity). If you do a little simple algebra you can manipulate the pump numbers and see that the 95 RON rating will be satisfied with 93 octane pump fuel. As altitude goes up octane requirment goes down, all else being equal. So you'll usually see lower pump numbers if you buy your pump fuel at higher altitudes.
 
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