Modified stock pipe saves big $$$


140 replies to this topic
  • 05-WR450F

Posted November 27, 2008 - 10:52 AM


My exhaust is complete. All baffles removed, stainless steel perforated core, shortened by 3", new Moose universal packing. Haven't rode it yet, just started it in the garage. Sounds great. Really like the look now that it's shorter.

Stock Exhaust
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Modified Exhaust (shortened 3" & removed baffles)
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  • ch_250

Posted December 07, 2008 - 07:25 PM


i'v been reading these posts and i tried the mod this week. started up my bike today and liked the sound. there's snow on the ground and wicked slippery, so i can't tell if there's a power difference. it's only a tad bit louder, but has a bit more of a deep sound to it. i have a canadian bike. i cut the end off and cut the first pipe a few inches to let the air in more directly. i would recommend cutting it a little more, other than that, it's perfect. i can't figure out how to put pictures on here, so i won't. if someone really wants them, let me know and i can get them to you.

  • ch_250

Posted December 31, 2008 - 03:14 PM


http://s474.photobuc...nt=muffler2.jpg

http://s474.photobuc...nt=muffler1.jpg

http://s474.photobuc...=muffler4-1.jpg

since i have a canadian model, i had to cut the end off. i did it right on the weld and when i had it welded back on, it looked great. not quite as smooth as new, but still very satisfactory. i wanted it tig welded but that's a specialty thing and much more expensive. i got someone to mig it carefully and he did a good job. if you take it apart and study it a bit its pretty simple how it works. i just cut the end baffle to allow more direct flow from the header to the end baffle. if i could do it over again i would cut it a bit further back. the pictures show how far back i cut it. i would go another inch or so. there is little sound difference this way, but we'll see once it's summer and i can really test it out.

  • Emms XR250

Posted May 13, 2009 - 10:40 PM


Sorry to dig up an old post, but can someone confirm if i remove the two rivets from around the end cap will the whole spark arrester mounting plate come out?

  • 05-WR450F

Posted May 14, 2009 - 02:52 AM


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This picture should explain it how the whole thing goes together.

You don't need to drill any rivets to get to the spark arrestor. Remove the end cap and the four bolts holding in the small pipe on the end. Spark arrestor is held in with the same four bolts.

  • Emms XR250

Posted May 14, 2009 - 09:06 PM


thats not what i asked

  • WR_Dave

Posted May 15, 2009 - 04:01 AM


Sorry to dig up an old post, but can someone confirm if i remove the two rivets from around the end cap will the whole spark arrester mounting plate come out?


Yes, but it's in there pretty tight. Go back to the beginning of this thread and view Dodjy's work and read the small instructions that I posted there from him.. He used a slide hammer attachment to get the end plate to come out.

Good Luck - WR Dave

  • Emms XR250

Posted May 15, 2009 - 04:29 PM


Yep got it out Dave thanks, only took out the first baffle.
We just popped a hole in it with a screw driver and 4 pounder, then got in there with an air hacksaw, did the job in about 10 mins.
Cant believe how much carbon was in there!
Now to go fit it and test it.:doh:

  • Emms XR250

Posted May 15, 2009 - 08:19 PM


This mod helped smooth out the roughness i get while trying to cruise at a constant speed, but as for power, it did nothing.
Will be ordering a "TK-Pipe" from this old guy that makes them in Queensland (Australia) he has giving me a guarantee that I'll love the slip on pipe and it will give 4hp, if not he will give me a full refund.
Says they sound nice and deep aswell.

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Didnt want to spend $495(aus) but im sure there is more power in this bike.:doh:

  • WR450FGreg

Posted May 15, 2009 - 11:57 PM


.

In my opinion any mod you do to the end of a stock '07-'09 WR450F muffler is negated by the fact that the first and (especially) second baffles are restricting flow.
If you can increase the size of the oriface sizes in each baffle as well as the tailpipe, you WILL definately notice considerable improvement in performance with the stock muffler.
I believe the only real gain from buying/fitting an aftermarket muffler (compared to properly modifying a stocker) is a reduction in weight.

You need to modify the oriface sizes in both baffles to see any real gain in performance from the stock muffler.

Study the diagram below and do the math before you spend $450!
(ie. calculate the area of the inlet pipe, then each oriface in the baffles. Then you'll see what I mean.)
eg. The first baffle's oriface size is half that of the inlet pipe!

Formula for calculating the area of a circle is: Pye x Radius squared

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Greg

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  • woods-rider

Posted August 03, 2009 - 07:54 PM


I know I'm diggin up something old, but I am tempted to take out the first and second baffles but can't afford for it to be too loud afterwords. Has anyone done this and tested the decibels? I would really like to know exactly how loud the bike would be. thanks!

  • WR_Dave

Posted August 03, 2009 - 08:15 PM


If you take them out and don't put in a perforated pipe and packing like Dodjy did, then it will be much too loud. I drilled 3 1/2" holes through the baffles and my bike is on the verge of too loud. Start sall and work your way up to it or get another pipe and experiment with it. WR Dave

  • woods-rider

Posted August 04, 2009 - 09:37 AM


Thanks for the quick response WR Dave! What about just removing or drilling some half inch holes in the second baffle? Should that keep the Db to a reasonable/legal level?

  • WR_Dave

Posted August 04, 2009 - 10:23 AM


If you look at all the pics that are posted in the first post on this thread you will see where all the baffles are. I would drill one hole at a time until you get the sound and performance you are happy with. You have to be carefull not to go to far and get greedy. I drilled 3 holes and I think itwould have been a bit better with only two. Mine are through both baffles though so the one at at time approach will let you sneak up on the perfect setting for your taste. WR Dave

  • WR450FGreg

Posted August 04, 2009 - 12:02 PM


.
Look at the existing oriface sizes (in each baffle and the end insert) in the diagram posted previously.
Do some maths before you start.
Calculate what sized holes, and how many you need to drill/punch before resorting to guesswork!
You need different holes in each of the two baffles.

BTW, anything you modify within the muffler is effected by the final, (end insert) outlet diameter you are running.

eg. You can drill 20 holes in the baffles, but if you're still running the same end insert then it's still going to be pretty much exactly the same muffler performance wise, just louder.

Greg

  • woods-rider

Posted August 04, 2009 - 01:03 PM


I took out the end insert. I am just running the spark arrestor and the end cap. I drilled one half inch hole in the second baffle and riding around the property it feels significantly better. gonna go for a real ride tomorrow so i can report back then. thanks for the help guys.

  • WR_Dave

Posted August 04, 2009 - 03:01 PM


.
Look at the existing oriface sizes (in each baffle and the end insert) in the diagram posted previously.
Do some maths before you start.
Calculate what sized holes, and how many you need to drill/punch before resorting to guesswork!
You need different holes in each of the two baffles.

BTW, anything you modify within the muffler is effected by the final, (end insert) outlet diameter you are running.

eg. You can drill 20 holes in the baffles, but if you're still running the same end insert then it's still going to be pretty much exactly the same muffler performance wise, just louder.

Greg


This is I why originally posted all of Dodjy's pics and drawings , so everyone could figure out the results of whatever they did. Obviously ( to me anyway ) if muffler mods are happening the first thing to go is the pea shooter tip from Yammie. Most just leave it at that, some of us build or buy a much larger sized outlet. No guesswork is necessary. I personally felt that 2 holes drilled did as much as 3 except the 3rd hole increased the noise a bit more. Just trying to be a good TT'r and help out if possible. Keep in mind this thread was for the guy's who didn't want to spend the bucks on an aftermarket muffler. To each their own. :thumbsup: WR Dave

  • tlegrande

Posted August 04, 2009 - 03:23 PM


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This picture should explain it how the whole thing goes together.


Is there any difference between this and the '09 WR 250F?

  • tlegrande

Posted August 05, 2009 - 07:45 AM


.
For reference..... this is what a complete '08 WR450F muffler looks like when you drill the rivets out and pull it apart....
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Those of us wanting to remove the two baffles (walls with the holes/tubes) will find it pretty easy to do once you pull it apart like this.
You can grind the welds away with an angle grinder and the baffles will come out easily and neatly.


Does anyone know the exact size of this screw? I have an 09 WR250F and I was trying to get the end cap off so I can do the exhaust mods.

Now that I've stripped it, should I try to drill it out or is there an easier way?

Also, can this be done without drilling out the rivets on the outside of the muffler?

Greg, do you have any other pics of your procedure? I've got a race in three weeks and I don't really want to go down this road unless I'm sure I can do it without messing anything up.

Thanks,

  • WR450FGreg

Posted August 06, 2009 - 02:16 AM


.
tlegrande,

Sorry mate, that's the only shot I took when I had it apart.
You can modify these mufflers without taking the big rivets out as long as you have very long drills.

My advice (for what it's worth) remains:
1. Make or buy a larger diameter tailpipe.
2. Calculate the oriface area of your new tailpipe using Pye x radius squared
3. Refer to the diagram provided previously and calculate the existing oriface (opening) area of each of the two baffles (they are considerably different).
4. Calculate what size holes and how many of each you need to drill in each baffle to achieve a constant oriface size right through the muffler.
NB: You will need different holes in each.
5. Drill the right number of the correct sized holes in each, don't just grab the drill and guess!

In this way I believe you will gain the maximum performance from the muffler at the quietest possible noise level.

My two cents worth. Maybe I'm a bit anal when it comes to this sort of stuff, but I like things to be logical and right.
It's just me. :thumbsup:

Greg
:worthy:




 
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