400ex HMF Jetting

[cmdr]

Hey guys, I need a little help with deciding what jets to use for my setup.

I have a 400ex with a HMF Sport Series slip-on, stock head pipe. K&N Air Filter + Outerwears pre-filter, stock air box/stock lid on. Temperatures here during the summer range from 65-90 degrees and humidity from 70-90. Elevation is around 1378 ft. I was wondering what main jet and what pilot jet to use. Thanks guys.

[400exstud]

With a quiet core I would run a 152 and a 155 or 158 without the core. The pilot would be a builders choice with those mods. Just a guess.

[cmdr]

In your opinion what would you choose for a pilot jet? 42?

[400exstud]

I am running a stock pilot jet and once the bike runs good it has good response. Only on the warm-up it is a bit lacking.

[cmdr]

I installed my pipe today and god damn, its sweet, my pipe came with a size 165 main jet and surprisingly it doesn't seem to be running rich but I'm going for a long ride this weekend so I'll see how it is for sure. Monday I'm going to pick up a size 42 pilot jet from my local dealer it should deffinately solve the 0 - 1/4 throttle problem. As far as I know the 165 main jet is a real keihin jet because it had the symbol next to the number.

[z400roosteR]

Originally posted by 400exstud
With a quiet core I would run a 152 and a 155 or 158 without the core. The pilot would be a builders choice with those mods. Just a guess.

Uh.....Dude you don't need to rejet for putting in a quietcore.

[Pwrov1]

So far I have not changed anything for my HMF slip-on. Seems to be fine.

[400exstud]

Uh.....Dude you don't need to rejet for putting in a quietcore.

Maybe on your bike but on mine it was required. If you have the core, put it in and put your hand behind your pipe and rev it up. The do the same thing with the core out. There is a big difference in flow.