04 400ex

[WheelerBob]

Just wondering if anyone knows why the recomended jetting for a 04 and newer 400ex is much lower than the 99-03 ex's even though the 04 and newer have a larger carb, you would think a larger carb would flow better thus needing more fuel not less. Just wondering if anyone knows why, btw im talking about HMF jetting specs. Thanks in advance for any replies:D

[WheelerBob]

anyone!!!!

why dont you email HMF?

[WheelerBob]

I did and they told me that previous jetting specs were a little on the rich side to be safe, but still they say a 165 for the 99-03 and a 152 for the 04-05 and according to honda's website the 04-05 has a bigger carb than the 99-03 which doesn't make sense that the jetting spec would be so much lower than 99-03 ex. I would think that even if there specs were a little on the rich side in the first place that with the bigger carb the specs should stay the same since a bigger carb should flow better, I would not expect the specs to be that much lower, If anyone has a reason for this I would really like to know before i buy the pipe and start the jetting. Thanks in advance for any replies.:confused:

[phildogg]

hey bro I have the hmf s/o on a 04 and jetted 142 main and 42 pilot. no probs here rode all day fri. guess it also depends on elevation.

[WheelerBob]

Did you use a 142 keihin or a 142 dyno jet? and did you move your needle?

[yamablaster24]

i thought all 400ex carbs were the same. :rolleyes:

[400ex28]

since when are 03-04 carbs bigger??:huh

[Chino]

Originally posted by WheelerBob
Did you use a 142 keihin or a 142 dyno jet? and did you move your needle?

i have a full system hmf i just put on, i used a 42 pilot jet and 158 main jet. that's a good starting point for you, hmf calls for a 180 main jet when i called them, hell, it wont even run with a 180. try a 158/160 and 42 pilot.

[WheelerBob]

[QUOTE]since when are 03-04 carbs bigger the 03 is not bigger according to the honda website the 03 400ex has a 35.5mm carb and the 04-05 has a 38mm carb thats the reason for my confusion.:confused:

[phildogg]

yes that is right bro the 04 &05 models have 38mm carbs. I used keihin jets. left my needle where it was.
phil

[TORO1968]

The carbs are actually the same. Honda just changed the measuring point on the carb body. ;)

Do a search for all of the details.

-Jordan

[phildogg]

Originally posted by TORO1968
The carbs are actually the same. Honda just changed the measuring point on the carb body. ;)

Do a search for all of the details.

-Jordan

Then why the differant jetting? I'm just going on what hmf had told me,not saying your not right. just curious also.
phil

[TORO1968]

I'm really not sure... I do know that HMF's advertised jetting for the 400ex was waaaay off at one time.

Wish I could help you, but I'm running a Keihin FCR...

-Jordan