Stock Exhaust Modification:

[Hondamaster5505]

Ok.. This is for all of you who can't quite afford an aftermarket exhaust. You will see a gain, but not as big as an aftermarket would give you.

Silencer:

1) Remove tip from exhaust. cut off the s/a. is about 2in.

[Hondamaster5505]

2) Drill two 2-in holes on the inside wall. right in the bottom right beneath the existing hole.

[Hondamaster5505]

3) Reinstall 2-in tip. Your done! heres why this works:

[red_rider38]

Did you rejet like you would with a slip-on? Was it louder, and if so how much? On my xr650r you remove the baffle for more power like the yfz450. I was wondered if I could do something similar in the 400ex.

[AnDy7]

i did kinda the same thing except took the screen and out it on the back for a spark arrestor. yes it is louder, are some power gains, and i didn't rejet. If you don't want to have to do all that you could always just keep the tip off to, but don't get caught without a spark arrestor!!

[red_rider_069]

Originally posted by AnDy7
i did kinda the same thing except took the screen and out it on the back for a spark arrestor. yes it is louder, are some power gains, and i didn't rejet. If you don't want to have to do all that you could always just keep the tip off to, but don't get caught without a spark arrestor!! i did the cut out that he showed in the pic above.. my dad was pissed but he did it for me.. then i cut the screen off the silencer and welded it back onto the tip.. so i had a screen spark arrestor.. and an end ti[ back on.. i didnt like how it sounds though.. no rejet needed.. and i didnt drill any holes in the esxhaust .. but if you drill those 2 xtra holes it will be louder..;)

[red_rider_069]

Originally posted by Hondamaster5505
2) Drill two 2-in holes on the inside wall. right in the bottom right beneath the existing hole. drill two 2" hoooles? isnt that too big?! lol i think more like 1 inch holes would be better? you might make a hole where u dont want to:ermm:

[Hondamaster5505]

Originally posted by red_rider_069
drill two 2" hoooles? isnt that too big?! lol i think more like 1 inch holes would be better? you might make a hole where u dont want to:ermm:

Oops, sorry.

I meant 2 1in holes. Not a 2in hole.

So yeah, 2 1-in holes underneath the existing.

[Hondamaster5505]

and btw, just cuttin the silencer out of the tip doesn't do anything. The key to the extra power is the 2 holes.

[jrafter]

found it thanks

[triple b]

Here is what I did to my father-in-laws 05 400ex
I modified the stock tip like your drawing but I welded in a piece of 1 ¼” stainless steel tube (Just to make it look like it came from the factory). I drilled holes in the internal baffle. And I re-install the spark arrester.
Re-Jet
Uni-Air filter
Drilled 4” 1 ½” holes in air box lid
For $75 bucks (Jets, Uni & Tubing) and a few hours I am very happy with the results. It is quite, legal and runs good
http://i185.photobucket.com/albums/x181/Triple_B_21/400ex/ThanksDesert044.jpg

[mooseracerX]

^^^ You guys need to get that 400 on the dirt its a little too clean ;). I had a 400ex end cap and I did that and put it on my 250ex and its louder than stock and not loud enough to get the cops called every time I start it in my yard so I'm happy. There is no way my dad would let me drill holes in the muffler though.

[Hondamaster5505]

Originally posted by mooseracerX
^^^ You guys need to get that 400 on the dirt its a little too clean ;). I had a 400ex end cap and I did that and put it on my 250ex and its louder than stock and not loud enough to get the cops called every time I start it in my yard so I'm happy. There is no way my dad would let me drill holes in the muffler though.

lol, not to burst your bubble dude, but all that cap is doing is MAKING it louder. Not adding any power. Its the holes that do it, lol.
All i had was a stock cut tip (same exact thing as a power tip) and it added nothing. i welded the core back in.

[mooseracerX]

Not to burst your bubble but really how much HP are you going to get out of a 250ex anyways? LOL

[powermadd400ex]

i bought a billet exhaust tip and it made it much louder
not HMF loud but very nice. it has the tip and a little spark arrestor screen.
http://cgi.ebay.com/ebaymotors/2-Billet-Power-Tip-Honda-400EX-400-EX-ATV-Exhaust_W0QQitemZ180239822682QQcmdZViewItem?hash=i tem180239822682&
didnt gain to much top end but a lil bit on the bottom end
i didnt drill holes but i think i will after seein this thread

[Hondamaster5505]

Originally posted by powermadd400ex
i bought a billet exhaust tip and it made it much louder
not HMF loud but very nice. it has the tip and a little spark arrestor screen.
http://cgi.ebay.com/ebaymotors/2-Billet-Power-Tip-Honda-400EX-400-EX-ATV-Exhaust_W0QQitemZ180239822682QQcmdZViewItem?hash=i tem180239822682&
didnt gain to much top end but a lil bit on the bottom end
i didnt drill holes but i think i will after seein this thread

ah man. dude, they ripped you off. All it basically is is a stock tip with the baffle cut out and a fancy design... You couldv'e done the same to the stock with a saw for free..

And also, I think the extra low-end is in your head.. The tip alone does nothing on the 400ex. Drill the holes and the tip helps a lot then.

[Hondamaster5505]

Originally posted by mooseracerX
Not to burst your bubble but really how much HP are you going to get out of a 250ex anyways? LOL

hmm.. 5hp? LOL

[red_rider38]

What if I just drill the 2 1" holes and keep the tip the same. Will that add power? My two friends that I ride with have 450's so I need all the little help I can get.

[mooseracerX]

Originally posted by Hondamaster5505
hmm.. 5hp? LOL
Yeah no kidding probably around 15-20hp. Don't get me wrong its a fun quad but not a speedster or racer for sure.

[powermadd400ex]

Originally posted by Hondamaster5505
ah man. dude, they ripped you off. All it basically is is a stock tip with the baffle cut out and a fancy design... You couldv'e done the same to the stock with a saw for free..

And also, I think the extra low-end is in your head.. The tip alone does nothing on the 400ex. Drill the holes and the tip helps a lot then.

but its SHINY! XD

[Hondamaster5505]

Originally posted by red_rider38
What if I just drill the 2 1" holes and keep the tip the same. Will that add power? My two friends that I ride with have 450's so I need all the little help I can get.

Sure you could do it, but i don't know if you'll see an increase. The stock tip is only 15/16 big.
Why not just cut the baffle out of it?

[XXXRACER165]

Hey Honda Master. Should I try this on my 440? I like my WB E-series but the stock system is so much more durable.

[Hondamaster5505]

Originally posted by XXXRACER165
Hey Honda Master. Should I try this on my 440? I like my WB E-series but the stock system is so much more durable.

ughh... I really don't know what to tell you..

Like stated in my previous post's, it WILL add power, but not as much as an actual aftermarket.

Now, if you have a stock exhaust lying around you don't mind tampering with, then I say sure, go for it and see what happens.

I would try it, and you might end up needing another 1/4in hole along with the two 1in holes, since you have a 440.

Worst case scenario, bolt the WB back on, no harm done.

[400ex28]

ive seen a couple people here that cut their stockers into shorty's.

[red_rider38]

Do you have pictures of the shorty? I'm going to go ahead and do this to my bike. It will still have Spark Arrestor, right? I read what they post but I don't understand. Maybe when I see it.

[red_rider38]

I found this while searching the forums
This is cutaway of the stock exhaust (http://home.earthlink.net/~gellett/exhaust/index.htm)

[Hondamaster5505]

The spark arrestor you have to make yourself. It's basically just a piece of metal mesh.

And thanks for finding that diagram. I was looking for it before but couldnt find it, so i had to make my own.

[red_rider38]

The diagram looks like he split apart the exhaust so he could cut the internal pipe that comes from the header into the 2nd baffle. I think I'll just go with the holes.

[powermadd400ex]

this might be a stupid question but can you cut that whole wall? or is it not possible j/w

[XXXRACER165]

If only I could make my WB header work with my stock muffler.

[red_rider_069]

Originally posted by Hondamaster5505
and btw, just cuttin the silencer out of the tip doesn't do anything. The key to the extra power is the 2 holes. i did it for the noise haha not for perfomance.. for perfomance i got ma yoshi :D

Originally posted by XXXRACER165
If only I could make my WB header work with my stock muffler.

please tell me your being sarcastic or joking?

[Hondamaster5505]

Originally posted by powermadd400ex
this might be a stupid question but can you cut that whole wall? or is it not possible j/w

Yes, you can cut the whole wall, but that would be just plain stupid. The exhaust would go right from the header to the back, like a straight pipe. With the 2 holes, it restricts it somewhat and still makes some of it go through the chambers, so it's not like running an open pipe

[XXXRACER165]

Originally posted by FoxHondaRider
please tell me your being sarcastic or joking?

Actually I'm serious. The problem with a stock exhaust on a 440 is that it doesn't flow good enough. If I could use the large diameter head pipe for better flow (top-end power) and utilize the stock muffler. Make it flow better, it would be just as good as my White Bros E-series.

[dariusld]

Originally posted by Hondamaster5505
but that would be just plain stupid.

:D :D :D :D :D :rolleyes:

Originally posted by XXXRACER165
Actually I'm serious. The problem with a stock exhaust on a 440 is that it doesn't flow good enough. If I could use the large diameter head pipe for better flow (top-end power) and utilize the stock muffler. Make it flow better, it would be just as good as my White Bros E-series.

no the e-series will be much better than the stock exhaust. Better sounding and more performance.

[mooseracerX]

^^^ Well I doubt that, WB are crap IMO. Both sound just as horrible.:rolleyes:

[red_rider_069]

Originally posted by mooseracerX
^^^ Well I doubt that, WB are crap IMO. Both sound just as horrible.:rolleyes: its obviously better than stock. but if you dont have money for a good aftermarket.. well i'd save up :D

[mooseracerX]

Yeah very true although I would probably save up for something else. But to each their own.

[drew3623]

I know this thread is a week old, but will this work on a 300ex too? I might do it to my 400EX but I would rather try it on my 300ex to hear how it sounds.

[gel1197]

I bought a "second" end cap off eBay to try this on my 05' 400ex. I drilled the holes and cut the "second" end caps spark arrester and baffle off. ( I did weld a new SS screen on the modified end cap) My quad does breathe better now and it's sounds cool. All for about $20.00. My question is if I ever want to put the original end cap back on will the holes I drilled effect the "stock exhaust"? I have a K+N (w/outerwears), this exhaust modification and I changed the main to a 152. I also put a 13 tooth front sprocket on and I am really happy with these mods. All for around $100.00 so I have more $$$$ for gas to ride!

[Hondamaster5505]

Originally posted by gel1197
I bought a "second" end cap off eBay to try this on my 05' 400ex. I drilled the holes and cut the "second" end caps spark arrester and baffle off. ( I did weld a new SS screen on the modified end cap) My quad does breathe better now and it's sounds cool. All for about $20.00. My question is if I ever want to put the original end cap back on will the holes I drilled effect the "stock exhaust"? I have a K+N (w/outerwears), this exhaust modification and I changed the main to a 152. I also put a 13 tooth front sprocket on and I am really happy with these mods. All for around $100.00 so I have more $$$$ for gas to ride!

Glad to hear!

The stock tip will just quiet it down, no harm done.