My 400 has a WB-E series slip on. Had it on when I bought it.
Now, Ive since installed an IMS 440 kit with 10.3:1 piston,
and removed the air box lid. Still has the E-series.

I am going to rejet now, and need advise.
The previous owner had a 160 main in there with his E-series.
What size should I step up too with the addition of the 440, and the removed airbox lid?

Also, I live at 5000 feet, but will goto Glamis too.

Please give opinions on what size main to buy for both elevations. (will rejet for glamis trips)
ps. The previous owner lived in Phoenix. The 160 main was for down there....

 

just adding this. the new dirt wheels has an article on the whole jetting thing. i havent read it yet saving it for last.

 

I live at like 200 feet. And i have a 165 main. My mods are as listed in my signature. I am unsure how big of a dif elevation will make but this may help a litle. I am also runnin a bigger carb though. Good luck

 

I ride at 8000 feet, and jet for that altitude. I have found on several ATV's and bikes that dropping down two jet sizes (with a stock ATV) seems to usually be correct for my altitude. On three different ATV's I have then put on a White Brothers E-series, a Uni filter and air box mods. When I rejetted for the mods I ended up right back at stock jetting. I don't know what a 440 kit does to your jetting, but my guess would be to start at one size larger than stock jetting for 5000 foot and a 440 kit.

5000 foot altitude = one or two sizes SMALLER jets
Air box and E-series = two sizes Larger than above (back to stock)
440 kit = ?- maybe one or two more sizes larger?

Hopefully some of those with a 440 kit can tell you how much they had to change their jetting from stock...

Good luck,
Lorrin