Hello. Back in October 1997 I purchased a brand new Honda Transalp, this very bike.

By the end of 2001, it was clear that the original silencer had a short life left. It had had one of the end pipes welded, sound was not normal and there was a steady supply of carbon from somewhere onto the rear caliper.
My friend Joan heard me comment this, and to my surprise and astonishment, he said "I'll make you one".
I started to gather information from here and there. I got a couple of pictures of two commercial mufflers internals, I talked to Josep Codina of SoloMoto30 (this guy knows a whole lotta things about bikes) and I contacted Per Oehl (the maker of the self-constructed muffler mentioned in Deti's site).
Then, Joan and I sat down to decide the final design. It had to be easy to make, in the sense that no fancy shaped piece was to be used. All had to be feasible from raw available materials he had in his workshop (stainless steel plate and pipe), operations on them should not be more complicated than welding.

After a few sessions done after his work, my new oval 100% stainless steel J&J muffler was made and installed. And it worked! My gratitude to Joan in the first place, who put the skills, time and effort; and to his bosses as well (these guys are the inventors of the unique Lavakan, a washing tunnel for dogs!), who were happy to let us use their materials and tools. Thanks a lot!

Go to the bottom for more technical details.
Here are the pictures. Click on any to double size.

	Components in a mid stage.
Joan, ready for work
	Joan at work
Components in a later stage.
	Hey, are you gonna shoot me? :-)
The silencer, ready for a final polish and installation.
	A "clean" righthand side of the bike.
This way, the bike sounded like certain US hogs :-) .
	Full view after polishing and installing.
Another, closer, view. Includes Pyrennaic mud :-)
	Side looks.

Some technical details:
 

• The whole thing (silencer and pipe) is made of 1.5 mm thick stainless steel, the thinnest Joan had. Original is (I think) 1 mm thick iron.
• Why oval? Because
1. was the best shape not to to contact with the inner part of my case carrier
2. was the best shape to keep the hot muffler as away as possible from cases and legs
3. was the coolest looking shape :-)
• How oval? Joan just put a cylindrical piece of tube under the press and some wood. If he had had a piece of another suitable tube (inner diameter equal to outer diameter of the main tube), he'd have pressed both at the same time. Instead, he made the "side" of the "rear lid" by bending and welding a piece of plate.
• In picture 4 above, one can see the two main pieces of the silencer. One consists of a 420 mm long piece of oval tube, where a pipe ends (actually a few mm inside it). The other one consists of a 140 mm long central "pot", closed in the left, open in the right, plus two pieces of tube, one 140 mm long (the left one) and another 280 mm long (the right one). The inner diameter of the internal piece is exactly the same as the outer diameter of the pipe, thus allowing not to do any welding or screwing or riveting between the front part of both pieces.
• This internal piece includes 64 holes.  32 are in the 140 mm long tube as seen in the picture; the 280 mm long one has its 32 in the 140 mm "inside the pot" part.
• The gas flow follows the pipe backwards (WRT to the bike), finds the pot lid, goes frontwards and is pushed to the sides through the holes. Then it goes frontwards again following the inner side of the pot. Later it bends and goes backwards again following the sides of the oval. Near the end, it has to bend again, go through the holes and find its way outside.
• The total section of 32 holes is slightly larger than the pipe section. As is the "pot minus pipe" section and also "outer oval minus pot".
• Why so long a connecting pipe? I meant to install that as far as possible from my wife's legs.
• A drainage hole was made on the top front part.
• Why didn't we stuff any fibre inside? Er... fibre ends up by becoming a nuisance (carbon deposits, sparks...). Besides, in case of need, I thought I just have to remove the rivets and pull backwards to have the inner piece in my hands, then just wrapping some steel wool would do the job.
• How does it affect performances? My impression is that it delivers as before up to 4000 rpm, a little less from 4000 to 5500, and better (not "drowned") above.
• How does it sound? "Bom, bom bom" at idle regime, "brrrrrrroaaaaaammmm" when pulling the throttle, "brrrrooaaaaaaiiiiiiiimmmmmmmm" when releasing it :-)