sweet i just dont like the whole 1.30 a litre thing ahh but 9 bucks to fill the tank is nothing get some odd looks from people at the servo rocking up in bright yellow :P

 

If a brand new stock KLX250S knocks with 91 octane, there is something wrong with the bike or you are going up a hill in high gear at very low rpms. Under no condition should a stock KLX250S in good state of tune should knock with 91, 89, or 87 octane if ridden properly. If you are riding properly, you should take the bike back to the dealer to get it checked out.

And everything TNC said is correct.

 

i have put over 17000 miles on my bike with 87 octane. i think it would be more of a lean issue if anything. there is no power to be gained on just octane. the diffrence you may feel in the car is the car recognizing the higher grade and running more timing. maybe the "knocking" your hearing is the timing chain being loose and making noise.

 

George at uptite recommends running some race gas in the huskys to help cushion the valves, so why not try it in the klx. Following in the thinking that more is better, I mixed VPc12 in the 09 klx250s. But it didn't run as well as just the straight 91 from costco.

Now with the BB350 I haven't tried it yet. Coming off a stretch of freeway the coolant boils out the overflow hose making a mess of the rear end (but only after a really hard stint), so I'm gonna try it once again thinking it'll run cooler and not boil over.
Anyone experiencing anything similar? Maybe a higher rated radiator cap would help?

 

Wrong. I've got some elephant repellant I will sell you. It works great*.

*Elephant repellant is not for use in Africa, India, Zoos or circuses.

 

My wife & I have been running the 351 kits sence I built the first prototypes back in January 09 we have been running low octane regular in them with no problem the 351 has 12.5:1 compression.
Bill B&B Cycle Restoration

 

People get confused with old V8 think. These small bores and more hemispherical shaped 4 valve combustion chambers are less prone to detonation and pre-ignition. Not taking anything away from the OP's comments, though. Think his main pt was the book says 87 r+m/2, and a sticker on the bike says 91. Ive detected light ping in mine, and my KLR under certain load/throttle settings too, so use mid, unless I'm in the mountains where 87 is fine.

 

Gotta go with Bill and TNC on this. Higher octane gas will NOT provide any benefit in terms of horsepower.

There is the same amount of thermal energy contained in regular gasoline as "high test" gasoline. The higher octane gas is rated such to show its resistance to pre-ignition (due to compression, heat, etc.)

I see people all the time (mostly with sportbikes) running the highest octane gas they can get thinking they are getting moar powah. I run 91 R+M/2 gasoline in my 6R only because there is a big sticker on the gas tank the specifies to only use 90+ R+M/2 gasoline.

The only thing that high octane fuel will do for you (unless you have a highly modified KLX) is make your wallet lighter. Maybe some of you are looking for weight reduction so have at it. For the rest of us, its a non issue.

 

That's the placebo effect kicking-in, unless your are just referring to lack of knocking. You must have some really crappy fuel in Canada if you're knocking on regular grade fuel. The KLX timing curve is not aggressive by any means and the compression ratio is low for the head and valve design.

The only time I've experienced anything close to knocking is with too high of a gear selected on steep uphill grades.

HOORAY, you're 'meeting emissions' on a bike that only puts out 1/4 the exhaust volume of what even a small car does, yet it has to meet the same proportional requirements... pat yourself on the back again, while your KLX gasps for breath as you ride.

 

At least rimbender got my point !
tremor38 said:"You must have some really crappy fuel in Canada if you're knocking on regular grade " Yeah ! You got a point !