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Has anyone used racing fuel or any other fuel additives? Does it make a difference?

besides smelling good? not really, unless you have mechanical engine mods to make use of it. get a kx250 if you need way more power.

*edit* on a side note, I do put stabil or marvery mystery oil in my gas for the really rainy season here, usually late winter, to early spring, because of downtime. only additive I use besides that is honda hp2 mix

I use VP Racing U4.4 in my KX125 and KX250. It is oxygenated and does make a difference I can feel. If I were to race my KDX again, I would use it in the KDX for racing, but not for non-racing.

And yes, it DOES smell good.

C-12 here,IMO makes a significant difference.It makes jetting sooo easy,very consistant unlike pump gas.No ethanol.You will not notice any diff.over pump gas without making tuning adjustments(jetting and timing).

I picked up a can of klotz racing fuel and mix. 40 to 1 and 1 to 1 mix with 93 pump gas and race fuel. It was on recommendation from a local shop and so I tried it and really like it better then just pump. Is there a performance difference? It feels like it I don't have a dyno. Burns a lot better imo. Carb looks a lot cleaner and such. Mpg dropped a lot tho. Tested it on an old saw man that sucker screams with it but youd have to hurry and cut a tree down in three seconds otherwise its already empty.

I usually now buy pump gas and try it out in the saw to see how it runs. Here in Ohio its kinda a gamble how much ethanol your gonna get and Ive bought non ethanol gas at the lake and WOW you can tell the difference but its as much as racing fuel imo sometimes.

Messing with the above didn't really change the need for jetting imo. I was jetted with 93 pump at the time. Runs a tad rich but that's ok I had a slight lean happening but turned out bent needle. So I might try a smaller jet and get back some mpg but I mostly just run pump on the trails and save the race fuel for the tracks and bigger trails.

I have never felt the need for any boosters or race fuel. If you don't know how much my bike has been modified, click the link in my sig line. Just like jetting for your ratio (32:1 BTW!) and sticking with it, I do the same for the actual fuel and 2t oil. I use the same Chevron Premium fuel and Maxima 927 every time. Consistency is key IMO.

Oooooh, just give it a try sometime.

The KDX is in a pretty mild state of tune. Even my first 220 with FRP porting, head mod, bored carb, rev pipe, etc etc, never knocked on pump gas. I mean, that still maybe 36-37 hp from 220cc. In terms of specific power output a stock 250 mx bike still blows that away.

Anyway, what I'm saying is that you don't need higher octane, running it will give you zero performance gains. But batch to batch consistency is better, and that can be worth something. I always did like SS109 though, buy from a good station, and always the same one. For performance per dollar, its the best way to go.

I've run pump, ethanol free pump, 100LL, homebrew pump/toluene mix, Sunoco race gad, C12, etc. Once you are jetted correctly for a fuel I'd argue the differences in performance are basically placebo. Once I had the timing and jetting all sorted even my heavily modified YZ250 lived on pump gas, a bike that had major porting work, a long rod, and compression tested over 250 psi.

In other words, save your money. At least for a KDX anyway.

6% toluene

Hands down one of the best seat of the pants mods you can ever do

Adds so much more lower end when the going gets tough

Mr. Wibbens wrote:6% toluene

Hands down one of the best seat of the pants mods you can ever do

Adds so much more lower end when the going gets tough

Care to explain how that is possible?

Mr. Wibbens wrote:6% toluene

Hands down one of the best seat of the pants mods you can ever do

Adds so much more lower end when the going gets tough

Where do you buy toluene? Isn't it used in insulation for trailers and in boots?

Easiest place to find it is paint stores. Sherwin Williams has it in my area. Quart, gallon, or 5 gallon pail.

The specific gravity is much higher than pump gas, lot s of heavy end hydrocarbons. I want to say 0.84 vs .74 specific gravity from memory. Basically, will run richer with the same jetting. If you don't need the extra octane (114) then all you gain is richer running without rejetting. Burn rate is marginally slower, but still plenty fast enough to run double the rpm a kdx is capable of (14-15k kart guys, and was even the goto fuel for f1 for a bit thanks to the high specific gravity and fuel qty restrictions).

reg pump gas 93 with mix at the local fire pit at my house. It catches real good. Burns soaked wood till dry.

racing fuel with mix I send wood particles in the neighbors yard.

Like I said has a different feel is it worth it......I dunno I put airplane fuel in a ford fairlane once man that thing was a beast but blew the top of the engine off. Perhaps a kdx is tougher and can handle a little more.

My overall benefit was I couldn't find a consistency at the pump regardless of same station. If I found that was the case mix it up with race to even it out. Non ethanol runs superb in the kdx hands down. Aluminum doesn't like ethanol. Is it different then regular Id rather have a better burning fuel imo.

Jetting really never changed imo ran a little richer if anything. Plug chop even showed that. However it burns quicker hence I think the less mpg. The ring on the plug so to say was a more defined then with reg gas as well. Food for thought.