Building exhaust help!

So my bike is a XS850, its a Yamaha Triple... I found that a Triumph 900 Header fits however the header is a 3-2, the center pipe is split between the 2 pipes like a Y. Anyway I want to make it into a 3-2-1, I know how I want to do it but my question is on tubing diameter and backpressure...

The collectors from the header are 1.88" (1,7/8) OD... Question is, when I tie those two pipes together what should the diameter of that outlet be? Should it be 2 inches?? Also its very hard finding a muffler for 2 inch... How bad would it be to downsize it to 1.75 before the muffler? I want a reverse cone muffler, with a baffle and packing. I want it loud but not deafening... HELP! I have to order pipes, bends, and a muffler. Just to re-iterate... when putting 2 1.88" pipes in a collector what should the outlet OD be? Bigger, same? What if it was smaller for more muffler options? Thanks guys!!!!

the stock pipes on the 850 are 1.5" anyways, so you're already oversized at 1.88".....personally, I made a 3-1 on mine, and went from 1.5" headers to a 301 collector, that outlets to 1.75" and then a dunstall replica muffler. it runs great, sounds great, and I love it.

focusinprogress said:

the stock pipes on the 850 are 1.5" anyways, so you're already oversized at 1.88".....personally, I made a 3-1 on mine, and went from 1.5" headers to a 3-1 collector, that outlets to 1.75" and then a dunstall replica muffler. it runs great, sounds great, and I love it.

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Hey thanks for the info! I'm not an exhaust master by any means. So on yours you end up going from a 1.5 to a 1.75, would it hinder my bike by going from a 1.88 to a 1.75? even though they both have the same outlet, but mine would be constricted, whereas yours opens up? Also say if I went to a 2 inch, since my header is already oversized would I loose to much back pressure?

My xs750 runs great with a 2" homemade exhaust, nice deep tone, and screams at the top. But i doubt it would suffer with 1,75.

Kawasaki ZX10 uses two 1.5" to 1.75" Y's (image) to collector and out 1.75 to muffler Can't see why you would have restriction issues or scavenging being a problem as long as you keep the 3-1 collector volume symmetric.

In the image I am using the Ti ZX10 pipe to build my CB750 pipe along with an Ti Akropovic SBK chunk I got new from eBay for $80