im pretty sure they all havew 38mm carb

 

I called the honda deal and they told me that 04 and down have the same part # 05 and 06 have a diff # check it out ....
This one got me too

 

I have an '05 and when I put on the new exhaust it didn't have a gasket for in between the pipe and slip on. The local dealer didn't have one for the '05 but we looked at one for the '04 and it was the same part just different part #. So just because the part # is different doesn't mean there is a difference in the part.


SPECS FROM HONDA FOR THE 2004

ENGINE

Engine Type 397cc RFVC air-cooled dry-sump single-cylinder four-stroke

Bore and Stroke 85.0mm x 70.0mm

Carburetion 38mm piston-valve with accelerator pump

Ignition Solid-state CD with electronic advance

Starter Electric

SPECS FROM HONDA FOR THE 2005

ENGINE


Engine Type 397cc RFVC air-cooled dry-sump single-cylinder four-stroke

Bore and Stroke 85.0mm x 70.0mm

Carburetion 38.0mm piston-valve with accelerator pump

Ignition CD with electronic advance

Starter Electric

 

I'm just going by what servicehonda.com told me

 

ok.. who knows if they are a different size, but lets ask this, all of the 400ex's have the same motor in them so why would honda go from one size carb to another in that short amount of time, you think that after all the bikes they have made that they would have known what would have been the best carb for it right off the bat, so my guess is all the 400ex's have the same size carb, only thing thst has changed in the last six years is the transmission and the plastics.

Wreckless

 

My guess is that they but a bigger carb on the new one to make them faster because of the other 400's out there .Like the Z400

 

Unfortunetly the 05-06 400EX's do not have a larger carb. The slide size is 38mm, however the butterlfly size is only 35.5mm.
Apparently Honda wanted to "add" alittle to the specs. Most carbs are sized according to the slide dimension, Honda just failed to mention that it is the butterfly size ie. the throat size that is the limiting factor to flow here. I have seen these carbs bored larger, however increasing the area through the slide and the butterfly area increases cost. CUB Racing.[img]i/expressions/face-icon-small-sad.gif[/img]