Modified stock pipe saves big $$$

140 replies to this topic
  • metalmaster117

Posted April 20, 2006 - 09:30 AM


ok i have been reading and researching this mod on this forum for quite some time now and i am ready too do it but waiting to be jus a little more confident. i do have a few question the wall the hold the spark arrestor in place can be put back in with rivet or bolt right? also can i run a it straight through with nothing but the spark arrestor?(without packing and stuff) also how can i make it more bassy i wanna make it sound like the yoshi pipe my uncle had on his drz250 real bassy. i wanna do this right the first time as i can't afford a new pipe. man i sucks ass been 17 and broke. oh and will i have too tune my bike up again. also will this be legal in california

  • WR_Dave

Posted April 20, 2006 - 03:04 PM


A friend of mine did a version of this mod without removing the Spark Arrestor mount. He used a hole saw on a long arbour (homemade) to cut a 1 1/4" hole through the two baffles.He also made an end pipe that completely fills the hole on the end cap. He had to cut the end cap hole a bit bigger to accomodate the new tailpipe. The bike sounds great, runs great and with the baffles still mostly in place the pipe is still pretty strong if it gets hit. You will have to jet a bit richer if you open the pipe up. WR Dave.

  • metalmaster117

Posted April 20, 2006 - 07:00 PM


but couldn't i remove the spark arrestor mount remove the baffles then put the mount back in place with new rivets. and can i run it with out the packing

  • RX808

Posted June 11, 2006 - 04:39 AM


Sorry guys to bring up an old thread. I only just read this thread yesterday.

I opened up my can on 05 wr450 and removed only the 1st baffle, left the spark arrestor in and have no tail pipe. It has really opened up the bike.

Now I went for a ride today and the bike runs great but started to pop on decel and idle was hanging. The bike also became harder to start and when the bike was hot the hotstart still wasnt needed.

Ive already got a 48 pilot in so I think a 50 will be over kill, needle is a red #4,
and bike runs great wide open so main doesnt have to be changed.

Ive only got this week to sort it out coz theres a race on sunday, and i dont really have any ride time through the week> I havent played yet but I am thinking of richening the needle 1 clip, but apart from that this thing got me a bit stoked coz I think the jetting is rich enough, any thoughts??

  • boer

Posted September 19, 2006 - 01:26 AM


A couple of months now since this mod. What are the general opinions now after some good rides with the exhaust mod done? Does anybody want to give some feedback?

Bottom line, I have a PMB insert and would like to know if additionally opening it up (removing the middle baffle between the first 29mm ID baffle and the tailpipe) will help more as I don't want to spend the money on a new pipe!

  • Dodjy

Posted September 19, 2006 - 06:50 PM


Just do it. You won't regret it. It will liven your bike up heaps and if you just take out the rear internal baffle with the 2 pipes through it (the first one you come to when you drill the rivets out and remove the end plate) it will not be too loud.

After about 6 or more months of riding with all baffles removed and a perforated pipe joining the header pipe to the tail pipe plus the muffler packed with muffler packing, my bike isn't too loud. It actually quietened down after a couple of rides. I think I packed too much packing into the muffler so I originally thought the perforated tube bit wasn't worth it but now I have no doubts that it was the right thing to do.

When I removed first internal baffle, it wasn't overly loud and I noticed an improvement everywhere in the rev range.
When I removed both baffles it was REAL LOUD but top end was even stronger. Low and mid range was slightly better too.
When I linked up the header, where it enters the muffler, to the bolt on tail piece (PMB insert in your case) with the perforated tube, I got a little more low down grunt but top end suffered slightly. The noise level is now very acceptable but I'm not sure about Db.

I'd do it again in a flash. I don't think you will ever get anywhere near the full potential from your bike unless you take out the first internal baffle and replace the rediculous tail pipe with something with a larger diameter. They are just too restricted for the gasses to flow through.

  • pkcof

Posted September 19, 2006 - 11:20 PM


I did it, played around with it, re-jetted it, played around some more and then bought a GYT-R pipe !!
The stock can is a compromise and thats that ... the GYT-R is a purpose designed performance pipe and at 98db i wouldn't change it for anything.
I still keep the (slightly modified) stock pipe for club rides that require a few less db but then off it comes - kinda hard to go backwards when you see how much you can gain from a decent pipe !!

  • Alley Cat

Posted September 19, 2006 - 11:27 PM


I did it, played around with it, re-jetted it, played around some more and then bought a GYT-R pipe !!
The stock can is a compromise and thats that ... the GYT-R is a purpose designed performance pipe and at 98db i wouldn't change it for anything.
I still keep the (slightly modified) stock pipe for club rides that require a few less db but then off it comes - kinda hard to go backwards when you see how much you can gain from a decent pipe !!

That says it all really! :thumbsup: :lame: :p :bonk: :eek:

  • boer

Posted September 20, 2006 - 12:21 AM


Hey alley cat, how you doing mate?

What pipe you running?

  • WR_Dave

Posted September 20, 2006 - 05:52 AM


Pkcof is right, there will be a better response from a purpose built pipe, but keep in mind this mod is for guys with more time ( to tinker) than money to spend. A new pipe around here is around $600.00 and I think that most of us would rather spend that kind of money on skid plates and rad guards, good gear, etc. If you are a rider that can get everything out of his bike then I suggest that a new pipe be ordered, but the rest of us will find cheaper ways to help our WR's perform. My .02--WR Dave.

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  • Ron R

Posted December 25, 2006 - 09:04 PM


600.00 for 2lb and 2hp.
I will take a poop and ride with 1 less bottle of gatorade in my back pack.
Im doing the hole saw thing in the morrning!

  • wr450rideruk

Posted December 26, 2006 - 10:18 AM


i just swaped mine for a yz can, looked down it and there is no restrictions what so ever, dosnt seem to make that much diffrence in power but is a little louder (not much mind to my standard wr can) i was expecting it to be a lot louder,
any one know if i will need to rejet my carb or do anything else ?
i allready have cut gray wire, airbox funnel thing and throtal stop screw done

  • ryder14

Posted March 27, 2007 - 02:51 PM


could removeing the exhaust cap and a spark arestor ruin you bike?

  • WR_Dave

Posted March 27, 2007 - 03:39 PM


Only if you don't rejet afterwards-you may run too lean at lower elevations. WR Dave.

  • ryder14

Posted March 27, 2007 - 09:34 PM


how would i rejet it please help me WR Dave

  • WR_Dave

Posted March 28, 2007 - 04:03 AM


Check the jetting guide in the WR Performance sticky at the top of the WR forum. I don't know enough about your ride area , riding style or what mods you've done to be of a lot of help, there are a few guys down your way that may be able to get you closer.If you are close to sea level I think the stock bike will be too lean especially if you open up the exhaust. Check out the guide and you can find a good setting to start with. Sorry --WR Dave.

  • MAC 450

Posted July 01, 2007 - 09:07 AM


I plan on removing the 1st baffle only, will that need any jetting adjustments?
I have stock jets and a YZ needle in the 3rd position, and all the "free" mods(grey wire,air box,AIS,throttle stop). I'm in So. Cal. about 2000-3000 ft.
Any info would be appreciated.thanks.

  • WR_Dave

Posted July 01, 2007 - 10:45 AM


Again, depending on how you ride, you will probably need to go up one size on the pilot if the fuel screw can't get you in the ball park and you might also have to move the needle clip one more notch down the needle. ?? WR Dave.

  • gelean01

Posted July 08, 2007 - 01:42 PM


Eh Dudes! I just did this baffle removement(rear Baf) with a cutting torch and large punch. I tried the drilling, way to much effort! Then I tried the torch on one of the weld's, as soon as the metal reached it's melting point "BANG" with the punch and hammer, the weld broke loose and on to the next. The torch worked great and what a clean job it made (10 minutes). Just to mention I have very little experiencewith welding equipment.

Also I left the tailpipe out. SHOULD I RE-JET ???

Also when I bought my 2005 wr450, it came with a 48pilot jet and another needle jet along with the manual. What size is this needle that comes with these bikes?????

  • KiwiRacer

Posted August 09, 2007 - 07:48 PM


I took the whole muffler to bits, Made a perforated tube out of stainless the same OD as the pipe, Punched a shit load of holes with a turret press ( I have access to a fin-power... Lucky me. But you could also just go to your local exhaust shop & buy a perforated tube, & basically made a YZF muffler, Straight through. Made the end stinger etc & used YZF muffler packing, Works like a YZF muffler & sounds like one too. :applause: If you just take the 1st & 2nd baffles out the bike runs better but the noise really starts to get to you, It's loud. I rejetted ( Bigger on the main ) as the bike will run lean up top. If you take a look & my garage you can see the size of the hole in the back of the muffler. :ride:


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