building your own slip on exhaust
I've always been a little frustrated with aftermarket motorcycle exhaust prices, for what is essentially a glass pack (a perforated tube wrapped in fiberglass) I wondered how difficult it would be to attach an automotive glass pack to the factory mid pipe. Since I recently aquired a new stock muffler I decided to chop up my old one. First I measured the diameter of the mid pipe were it entered the muffler. 2 3/8” While mufflers do exist that fit over a 2 3/8 pipe they are very expensive. Negating the entire purpose of this exercise. But I got to thinking the inside diameter of the mid pipe may just be the same size as the outside diameter of a 2 ¼” exhaust pipe. If this was the case it would open up a wide range of inexpensive mufflers that fit over a 2 ¼” pipe. The first step was to salvage as much of the factory mid pipe as possible. This requires cutting off the part of the muffler that overlaps the end of the mid pipe where it enters the muffler. I did this by using a high speed air powered cutting tool and cutting about ¼” inside of the forward weld on the muffler can. The can here is very strong, more then 1/8” thick stainless steel and took about 1.5 hours to cut through. This was the most difficult part of the build. Once exposed you can cut the mid pipe at the weld. I then brought the mid pipe to an auto parts store and test fit the 2 ¼” pipe. It was a good snug fit.
I bought a 2.25” section of tail pipe. I got 23” for $7.
Slid the pipe as far into the mid pipe as it will go. Marked the point of overlap and removed the pipe. Measured the insertion depth. Mine was 2”. Now I inserted the section of tail pipe into the muffler as far as it would go and marked the point of overlap. In this case for me it was 3.5” Now I just added those 2 lengths together and cut the tail pipe to this length. This will provide the maximum amount of overlap. In my case 5.5” . This minimizes turbulence, maximizes sealing, and provides plenty of room for adding baffles if you desire to quiet the exhaust at a future point.
Despite being a snug fit, a small amount of high temp RTV (the red stuff) will help seal the exhaust, prevent leaks, and hold the hole thing together. The muffler in this case buts neatly against the end of the mid pipe. A clamp can be added here but is not necessary.
After initial assembly I found the exhaust too loud for my liking (it is a 2 ¼” wide 9” long muffler) so I disassembled the exhaust and added some simple baffles to bounce the sound around a bit. This is done by cutting ½ way through the 2.25” connecting pipe with a hack saw and cutting some sheet metal in little half moons to fit perfectly in the cut outs. The exhaust pipe then holds everything in place when assembled. This modification is easily reversible by just sliding the half moon shaped baffles back out if you don’t like the changes.
A bracket can even be made from the factory muffler. The factory bracket is tack welded in place at the back of the muffler. By grinding off this weld the bracket can be removed, and reshaped to fit the new muffler. I found it easier to leave the sharp bend in place and reshape the bracket along the back side of the muffler to accommodate my smaller muffler. I then cut off the excess. Cutting just above the first decorative hole or “lightening hole” in the bracket. Then bending out a bracket on the removed portion allows the removal of the nut from the OEM bracket which is reused when hanging the new muffler. Place a strip of rubber or cork gasket material between the muffler and bracket and push the original hardware through the outside mounting hole and end most lightening hole with a washer and OEM nut on the back side. Finally I cut the end of the muffler at an angle “slash cut” for purely styling reasons, and I was done. notice no welding was required. Total cost to build was about $35. $23 for the muffler, $7 for the tailpipe, and a few dollars for some sheet metal from the hardware store. Maybe not as stylish as the latest offerings from the aftermarket but about 1/10 the price. and weighs about 1/2 what the stocker does. With a coat of black high temp paint I think it would look pretty good. I took it for a 150 mile ride and the bike seemed to perform pretty well with the jetting I used with the stock pipe. It was just a little soft off idle so the needles should probably be raised on clip. I just don't like loud exhaust any more though. this was realy just an experiment to see what I could do and I've put this one up for sale on a FZ1 forum for $50.
I've included some pics of the build process below.
weighing the stock pipe. not too bad for a stock pipe. I've seen some that weigh 25lbs.
OEM pipe ready to cut
decorative overlap finaly removed from muffler to expose end of mid pipe
ground off the weld holding the bracket to the stock pipe
a little scotch brite realy cleaned up that mid pipe. 5.5" tail pipe and muffler ready for test fit
reshaping the bracket to fit the smaller muffler
Nut removed from original bracket
weighing the new pipe about 1/2 what the original weighed
adding som baffling to quiet the pipe.
cuting the excess from the reshaped bracket and adding a slash cut to the end for style
the finished product
and for comparison the stock cannon
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