05 WR450 Exhaust question

Hi Guys ... I've looked over a lot of the threads and i find some vague references to the '05 WR450 muffler and i was wondering are there any modifications worth doing to get similar performance to a GYT-R or FMF pipe? (short of replacing it and spending big $$). I've heard of hollow coring it with good results but these reports have always been the 'friend-of-a-friend' kind and i have no real first hand information. It seems a shame to replace it because the basic design, casing, style etc are all there to begin with and it shouldn't be too difficult a modification ... your thoughts please ?

You have a few options. 1.) get a PMB insert ($50). It works and takes just a few minutes to put in. It will help with performance and is still quiet. 2.) Drill out the insert that is in your stock exhaust. It's very restrictive. You can see it when you pull off the end cap. It is riveted in, but a simple drill will take it out. This will also help and it's free. Other than that, you'll need to consider a new muffler. I just recieved the GTRY - Carbon Fiber. MUCH lighter than stock and sounds like it can breath (finally), but I did experience some backfire. Not sure yet if it's gonna be an issue or not, but one quick spin through the nieghborhood was impressive. It pulls much nicer and more smoothly it seemed. I'll try it at the track today and see how it performs there and report back.

Hi Guys ... I've looked over a lot of the threads and i find some vague references to the '05 WR450 muffler and i was wondering are there any modifications worth doing to get similar performance to a GYT-R or FMF pipe? (short of replacing it and spending big $$). I've heard of hollow coring it with good results but these reports have always been the 'friend-of-a-friend' kind and i have no real first hand information. It seems a shame to replace it because the basic design, casing, style etc are all there to begin with and it shouldn't be too difficult a modification ... your thoughts please ?

... ok thanks rickk, i'll be interested to hear of your success on the GYT-R. In Australia they are around the $650 ~ $750 mark and whilst i'm sure that the performance gains and weight loss are noticable it is still a premium price to pay. Good luck fine-tuning your jetting ...

Well had it at the track today. It's much louder of course, but that's ok. It has better low to mid range power characterics now. This is what I was after so I got what I pad for. Like another poster pointed out, Yoshi, FMP, Pro-Circuit all pretty much do the same thing, so you may be able to save $$ this way, but I think they are all about the same price. It's not cheap, there's no argument here. I would still consider drilling out the inner core that was described earlier if funds are tight. It'll accomplish the same thing and let the bike breath better. Mine is a little lean now, but I can fix that with jetting changes it appears.

Bottom line: I'm not sure it's worth the $400, but it does provide an improvement in throttle response and low end grunt. Only you can answer if it makes sense for you. Hope this helps.

... ok thanks rickk, i'll be interested to hear of your success on the GYT-R. In Australia they are around the $650 ~ $750 mark and whilst i'm sure that the performance gains and weight loss are noticable it is still a premium price to pay. Good luck fine-tuning your jetting ...
... ok thanks rickk, i'll be interested to hear of your success on the GYT-R. In Australia they are around the $650 ~ $750 mark and whilst i'm sure that the performance gains and weight loss are noticable it is still a premium price to pay. Good luck fine-tuning your jetting ...

I got the GYT-R propower slip-on muffler on the 250, it was about $570 from bikebiz. It is 98db, which isn't that loud. The oval mufflers are a lot louder. I strongly recommend it, it was the best cheapest one I could find. It is lighter than stock, sounds real nice and isn't that bulky. The endcap looks way better IMO than the GYT-R oval. I got a Procircuit Ti GP lowboy system on mine, it would have to be the most powerful system you could buy!

Any muffler you get will do wonders with the WR's, I tried everything with the stocker too. It sucks ass! Don't bother with inserts, they are a waste of time and money plus you won't find them here.

Try and get hold of a YZ450F muffler, the performance gain is quite nice indeed. I tried one on my bike, my two best mates got YZ450's with my bikes.

G'Day Pkcof, I converted my 05 muffler with great success. It is really a work of art inside. Take off the end cap (4 cap heads) unscrew the tail pipe (4 allen screws) make up a larger rear tail pipe from a flat bit of 2mm stainless and I think I ended up using 30mm stainless tube (the hole in the end cap fits snuggly into the end of the pipe - I made up 3 tail pipes and kept getting bigger due to the amount of back pressure still present). Next take out the spark arrestor (wire mesh cage), drill out the 2 rivets in the rear end plate (where the tail pipe bolts onto) and pull out the end plate. It is tight and I used an arm from a large puller to knock it out. A slide hammer would be perfect for this. Be carefull not to deform the end plate too much. Once out you can see why the 05 muffler doesn't work real well. The gasses enter the muffler via the header which is quite big and unrestrictive, hit the far wall of the first chamber, turn around and go through about a 1 inch pipe into the second chamber, hit the wall, turn around and go through either a small pipe or very small pipe into a third chamber (I can't remember sizes but they are about 12mm and 15mm and different lengths). Then it exits through the spark arrestor and tail pipe. I removed each baffle in stages from the rear and rode the bike. I noticed more power through the whole range as I removed each baffle. I used a drill and die grinder to take out each baffle along with the pipes. I found that the noise level was still relatively quiet when the 2 smaller tubes and baffle were removed but with the front baffle and tube removed it is f'n loud. Mates riding with me reckon it's not that loud but I dissagree. It is about the same as an aftermarket straight through MX pipe. The power is awsome, so much better than with just the stock rear plug drilled out. Replace the rear end plate and rivet it in. At the moment I have kept the spark arrestor in and I plan to make up a piece of perforated pipe (same diameter as the tail pipe) to go from the header pipe to the tail pipe, then I will pack the chamber with muffler packing. This should quiet things down a bit and probably gain a little power down low to mid range due to the longer effective length of the pipe. The bike revs more freely, sounds really nice, and now pops the front wheel up in 5th with a little pull on the bars. Jetting settled on 170 main, 48 pilot, adjustable fuel screw, needle provided in the spares kit with the clip up one from center (leaner), airbox snorkel and cutouts taken out and grey wire disconnected. 14/50 gearing (stock). Total cost - 3 hours, a little scrap stainless and argon and 8 beers (2 to plan the job, 2 during execution and 4 while admiring my handy-work).

Thanks Dodjy - very well put - especially for the details and results along the way. So if i read you correctly, get a few mates - a few beers - some decent tools - have access to a mig/tig and modify away ! - I'll let you know if i have similar results

I just did the first baffle behind the SA. What a bitch. I ended up breaking it out with a pointed chisel. Then I punched holes in the next one. Ill see how it works out next time I ride. It was a bit louder when idling and revving but not too bad.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now