I've heard of modifying the stock 400EX headpipe for more flow. How do you go about doing this? Does it offer quite a bit more air flow? Thanks.

 

"86atc250r" had a reply to some post earlier i read... he posted a web page and it had very nicely done drawings and neat actuall pictures of it... the only thing i found as a drawback was there was a need to cut open your pipe and you had to weld it back together... the web page is http://home.earthlink.net/~gellett/exhaust/index.htm
maybe 86atc250R will post a reply since he knows more then i do and could help you more..... hope I helped you out

 

I did this and made a pretty in-depth post on it a while ago...I just found the URL: http://forums.atvconnection.com/thre...B=1&TID=256880. If you need more details just e-mail me (zurc@wilkshire.net), and I will try to get back to you ASAP.

 

Well, on the silencer - I cut it apart for exploratory purposes. You can get pretty close to the same effect as I achieved by simply making a hole or two in the rear chamber wall. I'd offset it from the spark arrestor exit for extra sound deadening (don't give the exhaust a direct shot out).

I made a modification to the first chamber as well for some additional sound deading and flow potential, but it's not necessary... My pipe's noise output is barely distinguishable from a stock pipe, but I gained a noticible amount of low and mid.

Now, for the head pipe, there are beads of weld on the flange where it mates to the cylinder head. On some bikes, the welds are thick and restrict flow quite a bit. On other bikes they are very minor. The only way to tell is to remove the head pipe and check for yourself.

The difference will likely not be huge, but every little bit counts toward the big picture when you are modding your bike.