Jump to content

What's with mufflers for the XR600R/XR650L?

Recommended Posts

Can anyone explain to me why the mid-pipe on certain XR600R/XR650L exhausts gets substantially bigger before attaching to the muffler? In most cases it is actually the same size as the muffler where it attaches. The XR's only mufflers are a great example of this and so is my White Brothers E series muffler. On the other hand you have the more traditional mid-pipe shape from companies like FMF for the same XR600R. The midpipe is relatively the same size from the header to the muffler connection. Even high performance street bikes use this approach so why is it different with the big single?

I've been looking at replacing my White Brothers muffler lately because it doesn't have the discs nor the backing plate to make it USFS approved. I've been back and forth between the FMF Powercore 4 and the xr's only mufflers. I was wondering if the odd mid-pipe shape helps the XR's only mufflers flow better. From what I've read the XR's only mufflers are stupid loud and that would warrant a quiet insert for me and thus choking the high flow muffler, right?

Also, for anyone wondering- the White Brothers header that was installed on my XR600R is VERY CLOSE to the same dimensions as an XR's only header at both the cylinder and mid-pipe connection.

Share this post


Link to post
Share on other sites

My own personal experience and not something I read , but didn't understand. The extra ''chamber'' of the XRs Only pipes would give more low end torque , like a short open pipe , with nearly the top end of a longer exhaust. The XRs pipe can not give quite the top end of most of the others. True , a quiet insert is going to strangle the exhaust somewhat.  I've had a couple of different FMF pipes and like the PC-4 WITH the included and removeable spark arrester IN it.

  • Like 1

Share this post


Link to post
Share on other sites
3 minutes ago, JoeRC51 said:

My own personal experience and not something I read , but didn't understand. The extra ''chamber'' of the XRs Only pipes would give more low end torque , like a short open pipe , with nearly the top end of a longer exhaust. The XRs pipe can not give quite the top end of most of the others. True , a quiet insert is going to strangle the exhaust somewhat.  I've had a couple of different FMF pipes and like the PC-4 WITH the included and removeable spark arrester IN it.

Thank you for the explanation about the effects of having the extra chamber on the XR's only muffler. I also appreciate your insight with the FMF PC-4 because that's exactly how I plan on running it.

Share this post


Link to post
Share on other sites

The S A takes the ''edge'' off of the sound and gives it almost perfect back pressure.

Share this post


Link to post
Share on other sites
16 hours ago, JoeRC51 said:

My own personal experience and not something I read , but didn't understand. The extra ''chamber'' of the XRs Only pipes would give more low end torque , like a short open pipe , with nearly the top end of a longer exhaust. The XRs pipe can not give quite the top end of most of the others. True , a quiet insert is going to strangle the exhaust somewhat.  I've had a couple of different FMF pipes and like the PC-4 WITH the included and removeable spark arrester IN it.

That makes sense, any change in the pipe diameter is going to cause a reflection back to the exhaust ports, and I guess the effect is lessened at higher revs due to higher flow, or maybe the early pulse doesn't hurt scavenging/ramming back the escaping inlet charge at high revs.

Share this post


Link to post
Share on other sites
6 hours ago, XR650L_Dave said:

That makes sense, any change in the pipe diameter is going to cause a reflection back to the exhaust ports, and I guess the effect is lessened at higher revs due to higher flow, or maybe the early pulse doesn't hurt scavenging/ramming back the escaping inlet charge at high revs.

The last part I think you're thinking of a 2-stroke.

Share this post


Link to post
Share on other sites

It's true on 4 strokes as well, but it might be on a 4 stroke it's timed to be a suction pulse vs a pressure pulse, so the scavenging part yes, the stuffing part maybe not.

The effect isn't nearly as large as on a 2 stroke.

 

  • Like 1

Share this post


Link to post
Share on other sites

So, after all of this research I went out in left field and bought the pro circuit T-4 can. Everything I read said the T-4 was too loud but that's a very subjective statement.

I don't mind bikes that have a little bit of rumble but I don't like something that is unmanageably loud. For my tolerance the T-4 pipe is just that, manageable. I left the spark arrestor in it and at idle or low RPMS it's not bad at all. The only time this pipe really sings is when you're at WOT or wringing the XR's neck at freeway speeds. During those times I don't mind a pipe with some noise. I don't think I can compete with a Harley by any stretch but it's louder than a stock bike for sure. Since adding the pipe the XR has been running way better. Not a surprise since the White Brothers muffler wasn't designed to be ran with no disks and the back plate removed.

Also the T-4 worked with the White Brothers header. It slipped inside of the header and was a good tight fit.

If anyone wants a White Brothers muffler for cheap shoot me a PM.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

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

Reply with:


×