400ex and Warrior jetting

[Drtridr18]

After my Yosh. slip on, i put in a K&N power kit stage 1, ran much better and stronger, made my friend with the warrior even more jealous, so we put an E series silencer and power kit in his, stage 2, big change, but still has no chance:).

Question is, now that it's getting a bit warmer, when we're wide open top-gear like in a field, he'll be in 6th gear pinned, but says it won't quite rev out because it sputters in that situation-says that's whats probably keeping him from catching up...i don't hear it because i'm already ahead, but when we switch i notice it also...what part of the jetting needs to be changed, I did it per specs., as with mine.

And mine from time to time, the 400, from a wide open burst, when i quickly let off the throttle, it will backfire slightly??

Thank you for your time and help.

[Stunz]

My buddies Warrior does the same thing at WOT. He has the stock main jet (145) and a WB E-Series. In this case it's either lean or hitting the rev limiter.

In your case. The Warrior could be hitting the rev limiter or it might be to rich. Try a 150 MJ and 1 turn out on the air screw.


I also have a Yoshi on my 400EX. I run a 155 MJ 140PJ and a big hole in the air-box cover. To get rid of that backfiring, make sure you don't have any air leaks in the exhaust system. Then play with the fuel screw (back it out to add more fuel). If the fuel screw doesn't help, you might need to go to a bigger PJ.

[Stunz]

Originally posted by Drtridr18
After my Yosh.....
be in 6th gear pinned, but says it won't quite rev out because it sputters in that situation-says that's whats probably keeping him from catching up
....

He's on a Yamaha Warrior, your on a 400EX...that's what keeping him from catching up!

[ExVillin400]

its the rev limiter i got the same problem on my warrior. you can't do anything about it except change the sprokets for more topend and after awhile it will hit it but not as fast as now.

[RED121572]

The reason your 400 is popping on deacceleration is that your running a bit lean on the pilot.