The very first mufflers I put on my new FXDC were off a new Street Bob. I love the straight cut look. I wanted a little better sound than stock so I modified them by drilling a 1/2" hole in the baffle plug. I was satisfied, but I got a like-new set of Screamin' Eagle SP muffs and I put those on. Much better sound, but I miss the look of the straight cut muffs.

So, that brings me to another Street Bob muff mod. Cycle Shack makes replacement baffes for the Screamin' Eagle SP muffs for people who want a little more sound than what these street legal muffs offer. I got to thinking: Why wouldn't those baffles work in the Street Bob muffs? So I ordered a set of those baffles and put them in my Street Bob muffs this afternoon. It was dark by the time I finished, so I will install them tomorrow and report back on how they sound.

Here's the Cycle Shack replacement baffles. The Drag Specialties part number is 1861-0468. Price is $38.95.



Here's what the Street Bob muffs look like with the baffles installed. I used the screws that came with the baffles and only drilled two holes in the baffles to put them in. The Street Bob baffles have three holes and three rivets holding them in.



Here's a step-by-step "how to" for this mod, which I'm calling the "Jekyll and Hyde" mod:

Drill out the rivets on the SB muffs. Mask the area first with duct tape to protect the chrome. Knock the old baffles out. The glass packing will still be in the muffler. You'll note that it's a double layer. Pull it out and cut off enough to make it a single layer, then put it back in.

At this point you can just put the new baffles in, but they will rattle if you don't do this next step:

The internal head pipe inside the muffler that the original baffle slips over is 1-5/8" OD to accept a 1-3/4" OD pipe, which has an ID of 1-5/8". The ID of the header end of the Cycle Shack baffles if 1-7/8" ID tapering to 1-3/4" ID. So I had to get a piece of straight 1-3/4" OD and fit it inside the header end of the baffle so the baffle would fit snugly over the internal header pipe inside the muffler. This prevents rattles.

Once you've fitted this "adapter" pipe, slide the baffle in being careful not to snag the glass packing. Use a rubber mallet to seat the baffle the correct depth, which is about 0.2" from the edge of the muffler.

Now you've got to drill the baffles for the mounting bolts. The Street Bob baffles are held in with three rivets, so there are three holes in the muffler can. I chose to only drill out two holes to mount the new baffles. I did not drill the middle hole. I forget the size, but use a drill bit that will just fit through the existing hole in the muffler body. Again, mask the area around the hole with duct tape so you don't damage the chrome.

Once you've drilled the holes, all that's left is to do is insert the mounting bolts (which are supplied with the new baffles) and tighten them good.

Install the muffs and enjoy the sound.

Also, I eventually pulled the baffles back out and painted them with hi-temp flat black paint. I also used pop rivets to secure them. Looked much better than the screws and with all that rust showing.

 

Good info, nice job Gary. What's the diameter on the big end of the baffles?

 

I think that the mufflers would have looked better if you had used the rivets

 

The baffle tubes are 1-7/8" OD, 1-3/4" ID. I had to cut a piece of 1-3/4" OD pipe to go in the header end of the baffles so that they would mate to the internal head pipe inside the muffler

Also, because these baffles are so much larger than the std Street Bob baffles, you have to remove some of the glass packing. The std baffles are narrow enough to allow a double wrap. You have to pull the glass packing and flatten it out and cut off enough to make it a single wrap. Then you've got enough space between the baffle tube and the glass mat for the exhaust gasses to flow.

I hope these are not going to be too loud for me. I suspect they are going to be somewhere between 1.75" and 2.0" Rush muffs.

I don't mind moderately loud, but if these are obnoxious I'll probably wind up pulling the baffles out of the Screamin' Eagle SP muffs and trying them in the Street Bob cans.

 

Thanks for the info. I might try to fit a set of those in the stock tapered mufflers I have. I'll be interested in how you like the sound.

 

I don't see how you could use these on the tapered muffs.

 

You could drill larger holes and additional rows of holes on each side of the baffle plug on the stock baffles and probably have a good sounding stock muffler. Maybe you could have saved yourself a few bucks not buying the cycle shack baffles. Could you post a pick of the stock baffles?

As for the tapered muffler you can do the same if you use a hole saw and cut the weld that holds the baffle in, tap it out, drill as a above, reinstall and tack weld back in place.
CB

 

Nope. You should see these baffles. They are unlike any I've seen in a stock HD muffler. The mesh tubing that holds the glass mat in place in the tapered muffs, and is welded to the inside of the can on those, is actually welded to the outside of the Street Bob baffles. No way to get to the holes in the actual baffle tube itself to enlarge them unless you cut this outer mesh tube off first. Plus, you're still dealing with a 1-3/8" diameter baffle, which is never going to give you a deep rumble, I don't care how many holes you drill in it.

 

That is too bad, could have been an easy mod. You seemed concerned about your modified muffler being too loud so the opened up smaller diameter baffle could be the answer, just thinkin'. If you could post a pic of the stock baffle I would appreciate it.
Thanks, CB

 

Exactly, once they are removed the opening is just under 1 7/8. May have to mod the baffle a little but I bet it would work.