For my klx I BUILT A new 40mm diameter collector .

 

Wow, I bet that took awhile to get all those bends correctly welded up! If you took the pipe off you could take it to a muffler shop and have them bend one to match what you made.

 

It took a long time and many difficulties to cut and weld the tube with the right corner, but I did not want a bent tube.
Now that is finished I am very satisfied with my work .
I can say for sure is unique .

 

Muffler shop bending causes the pipe to shrink in ID causing restriction. It would take a company that could mandrel bend the pipe to keep the ID consistent. AKA not cheap. The cut and weld method is least costly if you or a friend can do good TIG or MIG welding.

The trick is to buy some mandrel bent tubing. We built a high pipe for an SR500, using a couple U-bend 3" radius and one 45° bend tubes. If you can get tight enough radius bends a lot of the welds up by the head can be eliminated. Less welds = smoother flowing surfaces inside. Problem is when bends are increasing/decreasing radius or the path to follow is complex, they require a lot of small cuts and twists of the tube. We had one cut at the head pipe, but we had more room for the head pipe to come out. With the bends we had a total of 4 welds not counting the collar at the head and one mount tab... my friend had done a number of pipes and expansion chambers before, it helped a lot.

Plain steel is relatively cheap, then get it ceramic coated. Stainless is more costly, but no coating needed.

 

The interior of the discharge is smooth ,
after each weld the matte
and polished with a small rotary sander .

 

Just curious, how long did it take you to build it?

 

Among prototype PVC various tests
to find the right system for
calculate draw cut and weld the parts in the right way it took about three months . O had to learn to weld with the
tig .