FMF Jetting?

[250EXstud]

Hey guys what size jets do i need? I have fmf powerbomb header and titanium 4 muffler K&N airfilter and holes in airbox lid.

[Matt102]

Is this on a 250ex

[250EXstud]

No my 400

[nky400]

I run a 150 main and 42 pilot on my 400. I have the PowerBomb and the PowerCore 4. I also run a UNI filter and two holes in the lid. I know our set ups are not the same, but our elevations should be close. Maybe this will give you something to go by.

[cals400ex]

i would personally go a little bigger than that. we dialed in my friends a while back. with a slip on and a K&N, it ran best with a 152 in the summer months. a 155 was needed in the colder months. we jetted this for the best performance. we would put a new jet in and then run it against my 400ex until we felt the best jet was in.

[TeamSe7enracing]

I recommend calling fmf (www.fmfracing.com) - they are really cool about helping with jetting questions when it comes to their headers and their pipes. We have had good luck with their tech support!:)

Originally posted by cals400ex
i would personally go a little bigger than that. we dialed in my friends a while back. with a slip on and a K&N, it ran best with a 152 in the summer months. a 155 was needed in the colder months. we jetted this for the best performance. we would put a new jet in and then run it against my 400ex until we felt the best jet was in.

this isn't the correct way to test jets. A leaner bike will run better than a richer bike soo thats not too good to have a lean condtion and just leave it this way but if u checked the plus and its ok then the bike is ok.

[cals400ex]

like i said in the post, we jetted his bike for best performance because that is what he wanted. his plug was tanish gray color so we knew it was in the ballpark anyways. we jet ours how we want, you jet yours how you want. i just wanted to clarify that i did say we jetted it for best performance. i understand it may not run the coolest with it lean, but it wasn't lean in the summer months according to the plug color, which isn't always accurate. also, nky400 said he is running a 150. he is using a complete system too. that is why i said i personally would go a little bigger. also, with some fuels anymore it is nearly impossible to do plug chops with the different additives in the fuel. i was running my bike with a 165 main for starters when all i had done was x-6, no lid, and uni filter. my bike was actually slower than stock with that big of a jet in. i put in a 158 and then i got a nice gain in power.