Best jetting setup for my 400ex?

[infantry317]

Could someone tell me what the ideal jetting for performance would be for my machine. I have a WB E-series slip-on, K&N w/Outerwear, and holes in airbox lid. I'm running a 40 & 155 right now. Could I go bigger and get a little more out of the engine?
Thanks.

[Pappy]

the only way to answer that......try it and find out. each engine reacts differently and it could ....or it may make less power. whats the plug look like now?

[infantry317]

Haven't checked, I'll get on it. Thanks Pappy.

[Dienamo111]

i ran 155/40 for a whaile and still wasnt satisfied, but like he said the only way to find out is to try different setups. I personally am happy with 158/48 i have no problems plus i love the results:)

[Predator36]

With the setup that you mentioned - 155 to 160 main jet with a 42 pilot. If you remove the air box or run the G T thunder intake you can go to 165 to 170 main jet and 45 pilot. With either one of these setups you can also remove the chock plate for better flow.

[Wheelie]

I have basically the same setup w/ a 40pj and a 155mj and it works great.

In fact, from my experience, the 155mj gave better performance than both the 158mj and 160mj.