I just Bought a W/B e series slip on for my 400ex.I was reading how they say that you can adjust or tune this pipe by taking disc's out or adding them.Has anyone done any testing with this to see what works well.My 400 is all stock except for small add ons such as a K&N filter outerwears on it and a W/B rev kit, along with about (8) 1" holes in the air box lid towards the back just incase a liitle water gets in there its not right on top of the filter to where it will suck it in the engine as easy. Right now I have a #40 pilot jet a #150 main jet in it and the needle in the middle position.The fuel mixture screw about 2 1/2 times out.I have just got a 14t and a 16t front sprockets to try we'll see what happens with those. Does anyone have any suggestions about the jetting that may make some improvements. I can't tell much difference in the way it runs from stock cant see where the slip on was worth it.Im in VA. and am at sea level temp currently is around 75 to 82 humidity around 65% to 90% normally. Any and all help is appreciated.

 

Have you done a plug test?

I would think you are running lean. Try 3.5 turns out on the fuel mixture screw and move up to a 154 main jet.

Try 12-14 discs in the exhaust.

Use a new plug and run it for about 15 minutes and run it really hard for about 30 seconds then stop and recheck the plug.

If you buy a Dynojet kit, then it is really easy to change the main jet without even taking the carb off the quad.

Good Luck!

 

Thanks for your help I'll ty it see what happens.Once again thanks.