The 400EX owners manual recommends 92 octane or greater. Premium pump gas around here is 91 max., so I add a little octane booster. I have been using Bardahl, but when I pour it into a measuring cylinder, there seems to be a lot of particulate matter in it. I've used it for a while, and haven't had any problems with clogged jets, but it is a concern. Anybody else using this? Anybody suggest another product?

 

I am using "trick" or race gas(114 octane) but in a 50/50 mix with pump gas (92 octane). Some of the additives in the boosters can make problems later so I would stay away from them unless you know for sure all they are is octane. I wouldn't waste money on going much above a 100 octane, I really can't say I could tell much of a difference.
Hope that helps

 

If your 400 is internally stock, 91 octane is fine. They recommend 92 but it won't detonate with 91 in it. A lot of my buddies run 87 in theirs with no problem. I am running 110-89 mix. But I also have a lot of internal motor mods that require that high of octane.

What cracks me up is people running 110+ octane on stock motors and swearing that their power nearly doubled plus 'it smells like a race bike'. LOL

 

Well I am glad that it wasn't just me that really couldn't tell that big of a difference. I think it burns cleaner in your motor and does help a little, but a "double" increase..hardly...maybe if anything a little less laggy and better pick up.

 

Ok, my 250R neds a top end rebuild soon, so I was wondering if I should start running a 50/50 mix with aviation fuel and 89 octane after the rebuild? My uncle ran that fuel in it beofre I had it but i have just been using pump gas.

 

The only reason really to run higher octane gas is to reduce ping or knock, or if the gas you have is just to low in octane to give you the performance the bike should have. Sometimes you have to run a higher octane gas because of compression, so there are a lot of factors in what makes people use higher octane gas. But "higher" is not always better, there is a thing called diminishing returns.. money no object I guess no reason not to but I would still mix it..50/50

 

I knwo you need to run higher octane in high compression motors, but mine isn't modified much, I did notice that wiht AV gas it didn't foul any plugs, and smelt good.

 

Fouling plugs hu??? Well don't solve the problem with gas you need to look at your carb settings, something is not set right.. its obviously running to rich try new jets...adjusting the air mix.

 

I already solved it. I had the needle clip position too low and I wasn't running at the right oil/gas ratio. I usually know most of this stuff except if it has to do with elctrical components, I just had to share that with you cause I didn't want you guys think i don't know what I am talking about, and the real reason why it fouled plugs after I got it is cause I was riding to my friends house on the side of the road real slow in a high gear and if you "putt" around on it, it'll foul plugs. I solved that though, and it runs a little better at High RPM's to

 

You want to run a higher octance if your experiencing detontaion (sound of pinging) coming from your motor. This is caused by to low of octane which ignites quicker than a higher octane. Say if you have a high compression motor and you try to run low octane gas in it you will have some very high heat and pressure in the cylinder because the compression of the motor will ignite the gas before the spark plug does. This causes extreme stress on your motor. For stock motors you dont need to run anything higher than recommended octane. Running too high of octane will actually leave fuel deposits, because as stated before it burns slower, so the motor won't get a chance to completely burn it off if the octane is to high.

Hope this helps.