Exhaust Popping

When I Ride My Kx450f And Wind It Out To About 8 Or 9 Grand And Let Off The Throttle, It Pops Like Its Trying To Backfire Out The Exhaust. I Am Running 92 Octain Pump Gas. Is It The Gas Thats Causing This? I Tried Running Mr2 Fuel In This Bike And I Notice That The Exhaust Pipe Glows A White Red Comming Out Of The Front Of The Motor So I Switched Back To The Pump Gas And I Am Getting The Poping Noise. With The Pump Gas There Is No Pipe Glow At All. Should I Run A Dufferent Fuel? Is This What Is Causing The Poping Maybe Not Enough Octain? The Jets Are Stock In The Bike And I Live In Windber Pennsylvania At About 2800 Feet In Elivation. Could I Possibly Need Leaner Jets?

I've got a yamaha yz426f same thing happens to me just lower in Rpm's, One thing that i've done is tighten the pipe at the head. That has seem to fix my problem, the vibration on mine is insane and it loosens it up. So before a ride I wrench mine down tight and it seems to help. Good luck

When I Ride My Kx450f And Wind It Out To About 8 Or 9 Grand And Let Off The Throttle, It Pops Like Its Trying To Backfire Out The Exhaust. I Am Running 92 Octain Pump Gas. Is It The Gas Thats Causing This? I Tried Running Mr2 Fuel In This Bike And I Notice That The Exhaust Pipe Glows A White Red Comming Out Of The Front Of The Motor So I Switched Back To The Pump Gas And I Am Getting The Poping Noise. With The Pump Gas There Is No Pipe Glow At All. Should I Run A Dufferent Fuel? Is This What Is Causing The Poping Maybe Not Enough Octain? The Jets Are Stock In The Bike And I Live In Windber Pennsylvania At About 2800 Feet In Elivation. Could I Possibly Need Leaner Jets?

I'm no expert, but I did sleep at a Holiday Inn last night. 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 www.ziptyracing.com

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