just a remark on a extremely difficult task.

I ordered one yesterday after I saw Dave's post of only one left. When I placed my order it said there were 2 left before my order, I got the shipping confirm it's on way.

Looks like they are sold out now. "Item is no longer available" is now posted on the denniskirk website.

Mine arrived yesterday and I took it out of the box.   No wonder it is loud - the exhaust passes straight through the muffler, and the angled holes in the perforated core angle backwards....and I see no evidence of any kind of packing in the outer shell - so the noise just kind of skips over the holes.  I believe I could make an oval piece of steel with a bend in the middle, and slide it halfway down the perforated core - then put a flat rod into the backside to hold the disc in place....while I use a rod on the other end to hammer the waver flat and expand it into the perforated core.  The exhaust will then have to pass out and then back into the perforated core - it is the same concept I have on the muffler I am currently using, except I can remove the core to work on it and on the Mac it is locked into place.

I did a test fit and mine has the same issues as DragBikeMike reported.......the flange is too big to fit into the head and the muffler clamps is too small.  Doesn't say anything good for their quality control!

I may have a fitment issue with one the Cafe' bike - my foot brake is very close to the stock header at the toe pedal.......if this muffler sticks out away from the frame any farther than the stock header - I may have to do something to the pedal to get more clearance.

I'm thinking to use the grinder.
make a plug that'll fit in the end of the pipe and fit 2 bearings to a shaft.
fix that shaft on a bar that's pivoted on the ground.
and use a thumbscrew to adjust the bar to a set distance
Then rotate the pipe to grind the outside of the flange.

I scribed the correct size on top, and begin wittling metal away with tools.

Dremel with router base was just too slow - but it was accurate in keeping things square.

I used a die grinder and carbide bit for the initial work to get it close to the scribed mark, then used the Dremel to get things squared up, then files to smooth out any irregular areas.....then a drill and flap sanding wheel to get a nice finish.

It took and hour to get it where it needed to be.  Now I will just spray a bit of ceramic exhaust paint on the bare steel areas.

It don't fit maybe the reason for the discount.

But personally, I'm disappointed in the bend quality.
These are not mandrel bends and even the straight sections are oblong.

Just monitor the flange/pipe wall thickness with a caliper.  When you get to 8mm (5/16") it should be good to go.  You can't see it when its all assembled so who cares if it looks a little ratty.