muffler slip-on: where do I cut?

[rthor]

I want to replace my rotted out mufflers with some after-market slip-ons. Where should I cut my existing pipe?
And what about jettiing...Will this modification affect my air-fuel ratio?

http://i145.photobucket.com/albums/r228/gutglue/IMG_0955.jpg

[bradleymaynar]

Is it welded on? I can't tell if there's a clamp in the photo, but the muffler doesn't appear to be welded to the header. I would think you should just be able to work the pipe off if it isn't welded.

To answer your question about cutting, I'd do it as close to the muffler/header connection. Odds are you're going to lose and inch or so of header pipe by doing this. So you may be forced to fabricate a new mounting bracket, or get an adapter pipe.

Before you order the new muffler, be sure to get a good measurement of the outside diameter of the header pipe. It will make shopping a lot simpler.

Hope this helps.

Brad bt

Just thought of another suggestion if you are forced to cut. Cut the muffler off a couple inches back from the end of the connection. Then you might be able to grind/cut the remaining piece enough to get it off without losing any of the header.

[chance_rider]

I want to replace my rotted out mufflers with some after-market slip-ons. Where should I cut my existing pipe?
And what about jettiing...Will this modification affect my air-fuel ratio?

http://i145.photobucket.com/albums/r...e/IMG_0955.jpg

I just installed after market universal mufflers on my '81 GS650G. I suggest cutting the pipe as close to the muffler as possible. When I did mine, I cut right next the the weld. I used a saber saw with a metal blade to cut the pipe; it was easy and fast. Measure the length of the existing muffler and the pipe diameter and get a new muffler about the same length. Most universal muflers come with adaptors to fit a range of pipe diameters. Also I supported the mufler off the passenger foot pegs with the brackets provided.

[rthor]

Thanks for the excellent help guys.
Yes, the pipes are both clamped and welded (welded to the inner header pipes only). I am forced to cut unfortunately, so I'll chop it off a couple of inches or so after the weld as per your suggestion and fit some adaptor pipe in place to tie into the new muffler.
But what about jetting...Will the new mufflers have any effect on this?

[Steve]

Depends a lot on the muffler. You will have to do chop tests to find out for sure.


.

[mark]

But what about jetting...Will the new mufflers have any effect on this?

You'll just have to wait and see. If you're sticking with everything else the way it is, you might not have to make much adjustment. But its hard to say until they are on.

[Chuckster]

Can you post a pic of this when you're done?

[rthor]

Sure...I'll photograph what I can and post. It won't be for a while though. The weather up here is still pretty cold!

[jpaul]

If you get one of the Supertrapp slip-ons, you should be able adjust the number of disks to closely duplicate the flow of the stock muffler and retain the stock jetting. I was checking this option out, as I noticed I will probably have to replace my exhaust after this year. On my 1980 GS750, the diameter of the muffler just after the weld is 2.5", the same as the id on the largest diameter slip-on from Supertrapp. If yours is the same, you should be able to cut the muffler a couple of inches after the weld, and then cut a couple of slots in the end to make it easier to squeeze the end down to fit over the slip-on.

[bradleymaynar]

On my 1980 GS750, the diameter of the muffler just after the weld is 2.5", the same as the id on the largest diameter slip-on from Supertrapp.

That's the same on the header, Mac I believe, on my 1100. The only problem I ran into was that the SuperTrapp was shorter than the previous muffler. I had to MacGuyver something for the mounting bracket.

Brad bt

[Jagir]

macgyver

Hey Brad bt,
Can you post some pics of your solution?
I just traded a case of browns for some Harley slip ons, but the mounting screws are really far forward compared to the mounts on my old rotten megaphones.
I'm wondering about the brackets I'll need to build...:?

thanks,

james

[bradleymaynar]

Hey Brad bt,
Can you post some pics of your solution?
I just traded a case of browns for some Harley slip ons, but the mounting screws are really far forward compared to the mounts on my old rotten megaphones.
I'm wondering about the brackets I'll need to build...:?

thanks,

james

Will do. Give me a moment.

Here you go.


You'll have to forgive the dirt and salt. I haven't washed the bike in a while. I used an existing mounting bracket off the peg mount and then used a multi-wrench (not sure where it came from) and used it to hang the muffler. My one suggestion would be to try and find some nylon lock nuts. I had to replace one of the bolts and nuts when they fell off. The lock nuts should ensure that they stay put.

If you aren't able to come up with a solution like I did, I'd recommend going to a hardware store and seeing if you couldn't get a length of flat stock that you could drill out to what you need.

Brad bt