I recently bought my 09 KLX250S (brand new). This bike is my first ever bike.
The seller told me to fill it up with regular gas. Biggest mistake: the owner manual says "minimum 87 octane" gas.
So...I've been driving my bike for 4 month now, drove about 2000km...using 87 octane gas.
I noticed some knocking when I was twisting the throttle and pretty good vibrations begining in the 6500rpm range. I didn't know what to think about that but as a green horn I didn't have the experience to figure out there was something wrong...
Until I had to remove the white plastiv cover located over the coolant overflow tank. A sticker inside the cover specifies...a 91 octane level minimum !
So I went to the gas station and fill it up with VPOWER gas (octane 91). Since the gas tank was already half full the octane level in the thank sould be around 89...And it makes a huge difference. More power, smoother acceleration and the knocking almost stopped. I can't wait to have a full tank with 91 octane...I will contact Kawasaki Canada to have explanations.

 

Well, that 91 octane isn't really required...at least if you're using the octane rating system that I'm aware of in my area. Nothing wrong with using a higher octane, but the stock KLX will run fine on 87 octane. I think you're situation probably involves the stock bike being too lean to begin with which aggravates detonation and such. From the factory these bikes are choked up on the intake and jetted down to meet emissions. When you at the very least up the jetting, like with a stage one DJ kit or such, the bike runs smoother and cooler and yields a little better power. The bike really comes alive when you open the intake a bit, replace the stock muffler, and jet up accordingly.

Bill Blue told me his original 351 kitted bike with slightly opened intake and exhaust mods would run on unleaded regular...85-87 octane depending on altitude...and that's considering his 351 kit ups the compression ration from a stock 11:1 to a 12:1. A stock KLX should run with 87 octane just fine if your jetting is upped a bit.

 

i dont know alot on this topic but i read a big article on yahoo that was all about compression and what octane rating to run. and i said that if you are higher than 9:1 compression u should use 91 octane. and it also talked about how running 100/110 octane can actually be bad for a motor which i didnt know that. it was interesting..

 

Every motor is different. Aluminum headed motors can run way more compression, and timing than the old cast iron head motors. That, and combustion chamber design has come a long way. Modern Honda, and Toyota cars are running up to 11-1 on regular fuel these days. If I can find 89, I use that. It's only under very heavy load, or low RPM's does it occasionally ping. I have probably used regular more than anything.

 

Thanks for reply TNC.
therfore I don't agree with you. The octane level DO make a big difference. As a mechanically encline person I noticed a huge difference using more octane. After all, why would they require a minimum of 91 if that makes no difference ?
I like my bike stock, I like the fact it doesn't drink too much gas and...yeah...I'm proud it meets emissions !
Thanks for reply again, It's always good to read you guys !

 

98RON all the way unless I'm in the bush, then you take what you can get.

 

just asked mike and he said to put 98 in it from bp so i assume that fuel is the best

 

Well, the reason you don't agree is probably because we're talking a bit of apples and oranges here. That 98RON that WOK is referring to is probably about like the 92 octane..or close...in the U.S. and maybe Canada. And I'd bet a nickel that the 91 required by the KLX according to Kawasaki is based on an international RON number. The U.S. uses a funky average of RON and MON to come up with what is basically referred to as an anti-knock-index...AKI. If we're going to discuss fine points of fuel octane, we'll all have to use the same exact standard of octane rating, or it won't make any sense...and doing that on an international site is going to be interesting to get everyone on the same page.

Here's one thing that I don't see disputed to any degree...and not by me but by engineers and people who do it for a living...higher octane fuel than an engine "absolutely" needs to carry out combustion without preignition or detonation provides no benefit to the performance of the engine. Do a Google or internet search engine of your choice to see that this is a fairly well agreed upon principle.

 

A very useful article on octane...
http://en.wikipedia.org/wiki/Octane_rating

 

Yup. Goes in the "scoobydoo" too. Likes it and I can feel the difference.