open her up a little, how well does she respond?

[rigger]

I have ridden plenty of 400's with all the normal pipes, and so on and they run pretty good with all that stuff.

My question is, how well does she run by installing one of those $30 ehaust tips, (or modifing the stock tip) open up the air box, grind the header welds and jet accordingly?

This is a similar set of mods called the "Gordon Mods" that are done to XR400's and that bike responds very well to the above metioned list of mods and it only cost a few bucks for jets.

I am wanting to open up my wife's 400 a little but don't have a bunch of toy money to spend right now. I have plenty of jets in the tool box and if I were to make my own tip, it would be some free ponnies for her.

[Wheelie]

The first mods I did to my EX was modify the stock spark arrestor and stock air filter, remove airbox lid, grind welds and remove choke. Jetted it to a 40 pilot, 152 main and lowered the clip on the needle one notch. Made a very noticeable difference in power for $8 in jets and about 1-2 hours of my time.

[dariusld]

Gordon Mod is alot of work, much more than changing the tip. The tip removal or change does nothing, but make your bike sound bad.
This picture shows why it does nothing.

[rigger]

The Gordon Mods on an XR are really not a lot of work. At least not to me any way. And they do wake up an XR a lot. I have done it to my own XR's in the past. I am only assuming that since a 400EX motor is pretty much the same thing, and the exhaust set up is also pretty much the same, the result would also be about the same.

That picture is a good at showing you what the inside of the pipe looks like. I know it is not going to flow as good as an after market ehaust but it has got to help some.

I played around with a stock 400EX end cap once. Just board and seeing what I could do with it. I cut the inside of the spark arrestor out and that opened it up just like the ones you see on ebay. But.... It did sound like crap. So I went to the parts store and found a little exhaust reducer that fit on the inside of the end cap. It stuck to the inside maybe 4" and reduced the hole about a 1/4" on the inside.

When I put it on, it actually sounded pretty good. Only a little louder than stock but with a nice tone.

I never rode on it so I can't say what it performed like. But it did flow more air than a stock tip and sounded pretty decent.

The next day my HMF system came in and it got put on.

DON'T BOTHER WITH THE EXHAUST TIP!!!!!

I can't count how many times people ask about this.. lol.

Modifying the tip, or buying the ebay one, does absolutely NOTHING. The internal chamber design does not allow for extra power, as the exhaust flows through different sections then into the little 4in section in the back. So it's already been fully restricted by then.

All removing the baffle does, is make it sound like an infant farting in a bathtub. Don't do it.

The ONLY way to get more power out of the stock exhaust, is remove the tip, and then drill a large hole in that wall towards the bottom. That will let more exhaust gases escape directly out the exhaust, instead of chambering through, but it will still sound like crap....

By the way, I know from experience. When I had a stock exhaust I cut the baffle out. It wasn't ANY faster and sounded so bad.. I welded it back in..

[rigger]

Got a pipe on the way now for her 400. Got to tinkering and drinking last night and the drinking lead to ebay and intern that lead to a by it now. I really do not have the toy money to spend right now but what is done is done.

I did open up the air box. Put a nice UNI filter in it. Took the choke out. Jetted her a little fatter and ground down the header welds. She should run alright once the new pipe gets on.