Modded stock exhaust

[XxxTRiPxxX]

has anyone riding a 400ex with the modded stock exhaust, if so is it worth it to do that over getting a pipe or better to get the pipe

[sly400ex]

The header pipe is excellent on the bike I have heard. A few simple mods and you can get your stock exhaust breathing pretty well. Do a search on this site for stock exhaust mods, and there will be posts to help you out. Nothing beats a full system though. Go pro-circuit!!:D

[fourtrax400ex]

i have a 400ex with the stock exhaust modded, i really like it, the mod make the stock exhaust flow like a slip on, i suggest to you to made the mod on the stock exhaust and try it, if you dont like it buy a slip on after, perhaps, a complete system with header add surely even more hp.

[4punksdad]

I modified mine...........then I bought a spare stock silencer in case I wanted to switch back. I didn't see any major improvement in power from the exhaust mod. I got more juice from the airbox mod I think.

["BLAHH"300!!]

i have a freind that races down here with a raptor
he still--or did--have the stock pipe on it-
he decided to cut out the baffel on the stocker to give it a little more kick..
he decided he didn't like it and reinstaled it-
one day while racing on a levey he was runnin' pretty good
and the stock baffel shot out the back and in that instant he noticed a major
power loss- enugh to make his body lean forwards when it came out the back
- ???? i though it gave you more power without the stock baffel than with- ?.. is this true-??

[Deathbringer]

EX-CITING 300


For exhaust mods to work "right" you need airbox,jet, and carb work. Yes you can loose power from just a pipe mod because exhaust needs "back presure" to work at its best. Too much or too little can have adverse effects.

["BLAHH"300!!]

i see nifty- that's why this site is the best..

i haven't talked to him in a couple of months
but.. last i heard he had it clamped down-(-shocks-)
and was getting sponsored through yammaha
he's been winning alot in the circle-flat track mx and drags
on his raptor-
- more power to him

[fourtrax400ex]

about the stock exhaust mod, if you really want a difference you need to open the exhaust completely like it explain in another post, just to remove the baffle and drill hole dont increase exhaust flow really.

hope it helps!

[WB400ex]

ill tell you this i have a white bros slip on the e series and one guy has a modified stock exhaust and we were at the sand dunes racing up a pretty big hill with whoops in it and we were dead even. i had stock jetting and he had a bigger main jet in the carb. so i think it only works if you do it right. he told me he took off the spark arrestor and he cut about 6 inches off the silencer and something else i think. but his bike ran good. we were racing another 400ex with the white bros r-4 slip on and he also had the jet kit with modified air box lid and all three of us were dead even

[Tommy 17]

from what i have read the stock header on the 400ex is great for not highly moded engines heres a perfect example.

Today i was reading the new issuse of dirtwheels december 2001 and they have the 400ex all stock but the pipe. 1st dyno run was the stock 400ex wit stock pipe it made 28.3 hp (88db), 2nd run was the 400ex wit the quite core 4 muffler only it was 28.8hp (93bd) 3rd run was the quite core 4 muffler and the power bong header too it was 29.0hp (93db). the runs were at 6750 rmp.

thats only a .2 more hp wit the bong on there over the stock header.

[Deathbringer]

Wow that is interesting...
I had heard that the stock header was good, so I guess now its just a question of money. If you want every little tiny bit of power, replace the header. Thanks for the article 400ex21

[3hondas]

also keep in mind that the stock silencer is considerably heavier than say a pro circuit t4. I did modify my stick exhaust by opening up a 1" hole in the rear baffle plate and replacing the tube in the end cap with the largest diameter tube that it would take after the tube in the stock end cap was cut out. Rejetted to 152 main. Small power increase and still quiet, but nothing compared to the pro circuit headers, t4 silencer, no airbox lid and dynojet 170 main. The difference is night and day when you install a lighter, professionally tuned exhaust system and take advantage of the better flow it affords you in the way of air/fuel mods. By the way, i am running the stock pilot jet. The bike vulcan screams.