Header mod

[Woodsrider]

Okay I did the header mod on my 400 last week. At the same time I did a valve adjustment, and that is it. I went to my freinds house for a ride and he could not beleive that was all I did to the bike.
I bought the bike used and it needed the valves adjusted to begin with.
here is the deal, If the int. valves were loose but the exh. were good, how much of the improvments were from the header mod?
I took out almost a 16th of an inch all the way around plus more in the high spots where the weld meets.

[Tlongs400]

not sure but it really picked mine up and alot better throtle response

[DESDAK4]

Same hear. My buddy has a the DMC Alien and I had the E-series and modded head pipe other than that at the time we raced everything else was the same on both bikes and it was dead heat racing just depended on the rider. So I figure at least for now I got 200 dollars for something else.

[Woodsrider]

I noticed it all in the throttle response. when you poke it, it really snaps now:D The front end got a lot lighter out of the turns, and my freind just could not believe the difference.
Now he is gonna take the header off of his xr400 and do the same :blah

[woodsrider400]

How do u do this what weld on the header pipe

[Woodsrider]

If you take off your head pipe, and look inside it, it is welded at the flange. The weld creates a restiction in the flow. use a dremmel and grind the welds down to create a smooth flow thru into the pipe, and reinstall it.

[DEAL]

Take your headers off, you will notice in the front there are welds , Take a dremel or file and clean them out till its smooth inside.
I guess its a little like porting your head pipes.:)

[MoparTrav]

is there anykind of gasket on the header pipe?

[Woodsrider]

NO

[skemp]

Yes, there's a copper crush gasket that is a one time deal. It is only a few bucks, but you should be okay without it. You have to scrape around by the ports to get them out, and I have heard of a couple EX's coming from the factory without them, so your's might not have them.

[Woodsrider]

I thought it was odd to not have a gasket when i removed the pipe. But I looked on the pipe and on the head, thinking it may have stuck. No gasket.
Your talking just like the one on the spark arrestor correct?

[skemp]

The headpipe gaskets fit into the exhaust ports between the pipe and jug. They are about 1 1/2" in diameter. Like I said, you might not have any. I do though on my '01 model.

[ChadEXer]

You can get the copper crush gaskets real cheap. i have always replaced mine when i take my exhaust off or get a new one!