Rejetting with HMF Competition slip-on only?

[mattn03]

I'm planning to buy a HMF Competition slip-on pipe for my 05 400EX. It's 100% stock, so do I need to rejet with the HMF Competition pipe?

[CarGuy7a]

Yes you will need to rejet. Anytime you alter how the air is entering or exiting a motor, a compensation has to be made to accommodate the changes.

I would go to either a 150 main or 155. You may as well get an after market filter also to see a little bit more gains.

[mattn03]

Originally posted by CarGuy7a
Yes you will need to rejet. Anytime you alter how the air is entering or exiting a motor, a compensation has to be made to accommodate the changes.

I would go to either a 150 main or 155.

How hard is it to rejet? HMF only lists 152, 160, 165, 170, 180, 190, and 42 Pilot in their jet kit. Should I get this or buy some individual jets somewhere?

[CarGuy7a]

Originally posted by mattn03
How hard is it to rejet? HMF only lists 95, 100, & 105 as available jets from them (https://hmfracing.com/shop/performance/jettingefi-kits/250ex-01-09-jets).

That kit you posted is for a 250EX not a 400EX.

The 400EX has hex type jets. Stock main jet is a 148 keihin.

Re jetting is easy. I find it easier to just remove the whole carb. Then you take the bowl off, unscrew the main jet and put the other one in and put it all back together and take a ride and see how it runs.

[mattn03]

Originally posted by CarGuy7a
That kit you posted is for a 250EX not a 400EX.

I saw that after I posted it :p

[yellow02400ex]

I put the hmf comp on my bike a couple months ago and love it

[CarGuy7a]

The easiest way to do it would be to just get the filter by itself and the jets separately. The kit from HMF goes from a 152 main jet and jumps all the way to a 160. That's a pretty large gap between sizes.

From jetsrus.com you can get exactly what size you want. I think they even sell some jet kits too but you can buy them individually just as well. That's what I do I just get them individual.

[mattn03]

Originally posted by yellow02400ex
I put the hmf comp on my bike a couple months ago and love it

What jets did you use after installing the HMF Competition?

[CarGuy7a]

mattn03 I see you are in Harrodsburg Ky. I'm only about 2 1/2 hours North of you so our jetting shouldn't be to different. I'd say if you put a 155 main in you should be pretty close if not spot on.

When I put a pipe and air filter on mine I ran a 155 and it was perfect.

[mattn03]

Originally posted by CarGuy7a
mattn03 I see you are in Harrodsburg Ky. I'm only about 2 1/2 hours North of you so our jetting shouldn't be to different. I'd say if you put a 155 main in you should be pretty close if not spot on.

When I put a pipe and air filter on mine I ran a 155 and it was perfect.

If I keep the stock filter & airbox and only do the pipe, do you think the 155 will be okay?

You must be around Cinci?

[CarGuy7a]

Originally posted by mattn03
If I keep the stock filter & airbox and only do the pipe, do you think the 155 will be okay?

You must be around Cinci?

My White brothers pipe recommended a 155 with a pipe and air filter only. Most of these exhausts are close in the way they run so I'd say a 155 would be fine.

Yep I'm about 30 minutes south of Cinci.

[mattn03]

Originally posted by CarGuy7a
My White brothers pipe recommended a 155 with a pipe and air filter only. Most of these exhausts are close in the way they run so I'd say a 155 would be fine.

Yep I'm about 30 minutes south of Cinci.

Thanks for the info! Where do you usually ride? Some of us from Kentuckyriders.com get together and ride Mountain Parkway, Bell Co, Harlan Co, Brimstone (TN), LBL, etc. You should join us sometime.

[CarGuy7a]

Originally posted by mattn03
Thanks for the info! Where do you usually ride? Some of us from Kentuckyriders.com get together and ride Mountain Parkway, Bell Co, Harlan Co, Brimstone (TN), LBL, etc. You should join us sometime.

My buddy used to have some nice trails but he got married and moved. I've just been messing around the house on mine but since I've been working like crazy I barely have time for even doing that.

We went up to Haspen acres the first weekend I had my 400 and I hated that place. It was soo rutted out from all the jeeps and buggies it was just horrible. We went to big rock in Maysville and it was a pretty good place. It was rough rocky riding but the trails weren't rutted like crazy.

Yeah those places you all ride is a LOOONG haul for me LOL.

[mattn03]

Originally posted by CarGuy7a
My buddy used to have some nice trails but he got married and moved. I've just been messing around the house on mine but since I've been working like crazy I barely have time for even doing that.

We went up to Haspen acres the first weekend I had my 400 and I hated that place. It was soo rutted out from all the jeeps and buggies it was just horrible. We went to big rock in Maysville and it was a pretty good place. It was rough rocky riding but the trails weren't rutted like crazy.

Yeah those places you all ride is a LOOONG haul for me LOL.

We have a guy that lives in California, KY that rides with us some times.

[yellow02400ex]

Originally posted by mattn03
What jets did you use after installing the HMF Competition?

my 400 had a hollowed out stock pipe with a power tip. I bought my hmf off ebay and it said it cam with a jet kit but i didnt so i put it on and i guess my quad was already jetted for the other pipe and it runs fine

[mattn03]

Does anyone have a good step by step instructions for rejetting? I've never worked on a carb before (I'm an EFI kinda guy!)

[Ian400ex]

Originally posted by mattn03
Does anyone have a good step by step instructions for rejetting? I've never worked on a carb before (I'm an EFI kinda guy!)
Quick run by..[list=1]
Turn your gas off, burn the rest out
take all plastics off
detach the hose going from the tank to the carb
losen the clip holding the engine and carb together same for the air filter
pull the carb out and turn it upside down
BE CAREFUL NOT TO STRIP YOUR SCREWS GETTING THE BOWL SCREWS OUT
[/list=1]

[mattn03]

I got the HMF Competition pipe & 155 jet installed today. The pipe was a breeze and the jet was only slightly more difficult-mainly time consuming. The pipe sounds great, but I am a little surprised how loud it is! :eek: It shipped with the Stage 3 tip installed so I fired it up with that-WOW! The neighbors won't be too happy with me! :mad: I decided to try out Stage 2 and it's pretty loud too. I might throw the Stage 1 in just to try it out. I'd rather have it pretty mild so I don't bother the neighbors and then put the Stage 3 tip in when I ride at OHV parks. I still have the stock airbox, filter, and lid and it really picked up the power. I'd recommend this mod to anyone! :D

[JOHNDOE83]

I have a jetting thread.

http://www.exriders.com/vbb/showthread.php?s=&threadid=441780&highlight=plug