I don't see it on his site, but Bill states in a post on ADV that his kit has 12.5:1 compression. The stock KLX250/300 shows 11:1. Do any of you have any detonation issues when you can't get high octane gas? Several stations I've had to stop at in backwater spots in Utah, Colorado, and other places occasionally only had regular. This wasn't an issue on the KLR650, but I'm wondering how it might affect the KLX with 12.5:1 compression with the 351 kit.

 

I'm interested in this too TNC. My little KLX seems to prefer high octane...and my solution has been to keep a bottle of octane booster in the truck to mix as needed.
I'd like to go the BB one day.

 

As rule most bikes in this compression range prefer high octane at least 95 or above. But in pinch you got use what is available.

Octane booster should work just fine.

Interesting cannot really test both ways until we get a break in the weather.

Wonder if Bill follows this sight and get his take on this.

 

I use 91 and 93 on my bike only, haven't tried anything lower so I can't comment.
So disregard this post.. hahaa

 

Hello All,

You should be able to run the low octane gas in the KLX 351 with no problems. We only run the low octane gas in our bikes.
Bill
B&B Cycle Restoration

 

You know...I thought I had read in one of the many posts and threads on the 351 that you guys may have been running regular unleaded, but I couldn't find it anymore.

anomad, I'm surprised you have to run higher octane or have to use an additive in your KLX. I know yours is bone stock, and I speculate your situation might be based on lean jetting rather than the raw fuel requirements of the engine. I've run 86 and 87 octane regular unleaded in my '06 with no pinging. Mine is uncorked, of course, and the jetting is spot on for my intake and exhaust mods. I think that's why I don't get detonation. My '01 KLR650 would detonate with lean jetting. I had done all the pipe and intake mods except the backfire screen and had spot-on jetting for those mods on the KLR. When I removed the screen, I had pinging at WOT. One step up on the main jet cured that. It wasn't that the base motor design required high octane fuel, it was just a jetting issue.

The base KLX250 at 11:1 will run low octane fuel with proper jetting, but I was wondering how the 12.5:1 big bore kit would do. Bill Blue has never struck me as your common snake oil salesman, so I'd bet proper jetting on the 351 does just fine if he says so. I normally try to use 91 octane at the pump in my KLX for singletrack riding, as the occasional lugging of the motor is more critical for detonation. Riding on the pavement and riding in more open areas like the 2-tracks in Colorado and Utah are usually not as hard on octane requirements as accelerating out of slow singletrack corners and such.

 

I haven't had knocking, it just seems to rev up more willingly with higher than 86 octane.
Our regular unleaded up here is 85 or 86 octane depending on elevation. It runs ok on it, just seems better on the good stuff, could be placebo effect? The lean jetting should be just right for higher elevations.

I get slightly better fuel economy in my truck with midgrade vs. the 86, but not quite enough to justify the extra cost.