Fuel Question

I Have A New Kx450f And Have About 5 Hours On It. I Noticed The Exhaust Hat Black Residue In It. Is This Caused By The Fuel I Run In It? I Tried To Run Mr2 Fuel In It For About An Hour And Noticed The Pipe Comming Out Of The Head Of The Bike Was Glowing White/red, The Color Of Steel When You Form In. So I Switched To Pump Gas From A Local Sheetz Store, 92 Octain, And Now My Pipe Does Not Glow At All Any More And I Notice The Black Residue In The Exhaust (mufler) Pipe. I Am Thinking The Exhaust Should Be Clean Not Black??? Is This Normal? What Is The Best Fuel Type To Run In This Bike? What About Mr9?

your running way to lean while using that race fuel. Thats making you bike run really hot and causing lots of damage.

MR2 in a four stroke??? ever heard of Ultimate 4 ??? what elevation are you at???? For anywhere under 2000 feet elevation, and a relatively low humidity, throw a 170 main jet, 42 pilot, fuel screw at 2 1/4 out, needle on the 3rd clip, and the 55 leak jet. if the header pipe is glowing that is an overyly lean condition, like mackeymx said, however, if you sit and let the bike idle for an extended period of time with the choke on, it will do that too.. try to get some good fuel in it, either U4 or 91 pump, quit listening to everyone else about fuel, and go out and ride, 5 hours on your bike is way too new to start experimenting with highly oxygenated fuels, especially MR2 or 9 :thumbsup:

Ok Thanks For The Advise. I Just Hope I Didnt Do Any Damage To It. I Think I Am Around 2300 Feet.

Do I Need To Adjust My Carb If I Run Pump Gas 92 Octain?

I Am Going To Adjust My Fuel Screw A Little To Eliminate The Poping When I Decelerate Probably 2 And A Half Turns. I Hate This Problem.

There is No reason to run anything but good quality pump gas in your bike. U-4 will give you a boost in power, But the money you save every month running pump gas will be enough to buy a new rear tire (witch will improve you lap times more than fuel will).

Ok thanks. Can I ask one question then. The pump gas makes my exhaust run black inside. Will this eventually clear up if I continue to run it in the stock condition with pump gas? I raced 2 strokes all my life and these 4 strokes are way different. I just want to make sure I do things the correct way. I am just not sure if I would need to make the adjustments that were suggested earlier.

I posted this in an earlier question you had, but apparently you missed it? You need to turn the Fuel screw, located on the bottom of the carburetor, out to richen the mixture a little. From the factory its set at 2 turns out. You probably need to go 1/4-1/2 a turn more, since the weather you are riding in is probably pretty cold. And the gas in your bike, 92 octane is perfect for your machine. All the dirt bike mags test the bikes on 91-92 octane. Your header pipe glowing red is normal on any 4-stroke bike that sits and idles to long. If you cant get the popping noise to stop buy adjusting the fuel screw, you need to step up to a 45 pilot jet, stock is a 42. Invest in a longer fuel screw that can be easily turned by hand at www.ziptyracing.com

A little black soot on the end of your pipe is normal. The only way to see if your jetted correctly is to inspect your spark plug.......


who is mxonly that works at lee's that was a pro mx and a factory tuner

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