header pipe diameter?

What is the outside diameter measurement of the Yosh RS2 full system header pipe and the 400E pipe? :thumbsup: I have a 400S and was wondering how much larger the other two header pipes are. Mine measures 1 1/2" O.D. The only other 400 I have seen to check was a Quad with the 400 c.c. motor in it. It had the keihin carb and its header pipe was 1 1/2" O.D. I don't know if the quads share the same exhaust system as the 400E.

I don't know the exact measurement but look at it this way. I'm pretty sure all aftermarket exhaust companys must use the larger diameter (E) size tubing. What performance good would it do to make it smaller and also have fitment issues? I run a stainless E model White Brothers head pipe and it fit right into my FMF Q mid pipe/ can.

thanks for the answer, but not the info I asked for. Can someone throw a caliper on their Yosh header pipe or 400E pipe?

BTT someone must know the answer.

The Yoshi ti port is just a RCH under 39mm

Hi toy, :busted:

The E headpipe outside diameter is 50mm,

and the S/SM headpipe outside diameter is 47mm. :thumbsup:

Had to wait a little while for mine to cool off... :thumbsup:

Take Care,


It all depends where you measure it...

My E header was about 41mm & the staintune was about 45mm...

You're right... I measured the tubing diameter reading the wrong end of the vernier! :thumbsup:

Thanks for the correction...:thumbsup:



This is where I have been measuring for comparision.

I'm just trying to find out if the yosh pipes are significantly larger before I install my jet kit, MCCT, and other parts I got yesterday from the TT store. I'll wait to rejet if I decide to Yosh it. 2007 DRZ400S 175 miles on the odometer

the head pipe diameter is only a small part of the equation.

So forget the full system and just do a slip-on ?????? Use the stock small header pipe and and rejet for it?? I plan on leaving the motor S stock except for 3x3, rejet and exhaust. are you saying the yosh upgrade isn't needed? Bike will be a 50/50 street/trail ride.

uh,no thats not what i said.

i said the head pipe diameter is only one part of it.there is also length,taper,how much mega phone is built into the muffler.

slip ons make alot of noise and little gain.

Eddie. thanks for the clarification. :thumbsup:

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