I just bought a downswept expansion chamber for my rougher of the two JTs. Unknown manufacturer. I’ve been wanting to find a downswept pipe for any one of my bikes and they are just hard to find. So now all my little ones will have the crispy crackle. 

imgur.com/a/3eejUjs
 

Schu they look great

Well I've bought 8 expansion chambers for my enduros and this downswept is the first one that didn’t fit as advertised. The seller will take it back for full credit because he claims to have gotten the pipe from a Yamaha dealer that closed up, and the pipe was marked for a JT.

But I really like the pipe so I have chosen to keep it and do some creative fabrication. The center mounting bracket attaches properly to the right side engine cradle bolt. And the back half of the pipe lays in nicely and leaves just enough clearance to the rear tire.

However the connection at the cylinder is way off. It makes me wonder if this pipe was made to fit a performance cylinder and head combo. I know Webco sold performance heads, but I am not aware of any aftermarket performance cylinders that may have had a different exhaust outlet.

So I took a donor stock exhaust and cut off the head pipe portion. If I perfectly cut the head pipe about 3 inches from the threaded collar, then rotate the cut portion 180 degrees, then butt weld the pipes back together, it will give me the exact S shape that I need to join up to the chamber in the exact same place that the improper head pipe is connected. The head pipe diameter on the donor exhaust is exactly the same so hopefully this all works out as planned.

I will most likely take on the task of making the new pipe sections to the exact requirements. But I will probably have our incredibly talented sheet metal fabricator at work do the welding. My son is a pretty good welder and has various types of welders. But I had asked him to tack weld a nut to the body of a Bassani pipe and he accidentally blew a hole thru the metal. It was surprisingly easy to do. He then brazed the nut and filled the hole.

Edit #1
Added photos based on description above. Ignore the parts bike being used for fitting purposes only….

Scroll upwards for more photos..
imgur.com/a/BI71yKe
Scroll upwards for more photos..
imgur.com/a/eZboW0P

Edit #2
Almost forgot about the kickstarter clearance. I have one with a slight offset, but it will need a slight increase to the offset. I can handle that.
imgur.com/a/NkzBrIX