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The Blueshopsupertrap

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The Hermit had this idea so I thought I would give it a try. I had an old 3" supertrapp laying around from a bike I parted out.

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My original attempt weighed in at about 2 pounds. I started grinding and cutting and now it is a little over a pound. It is too loud for my neighborhood at 8 discs, but I will start adjusting and see where it goes. I will make a new heat shield for the exhaust soon. I think the 4" would have been a lot easier to make, and make lighter. It would look alot better on the X also...but. 👍 go Hermit!

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Awesome machine work there, blueshopsuper!:worthy:

If 8 discs is way too loud, and if you are entertaining comments, then I would start by playing with the size of the opening into the discs. I think the stock silencer needs back pressure to function (why I don't know, but anyway...:busted:).

The Supertrapp people say the entrance to the discs should be the same size as the ID of the discs for best results. For the 3", that's 1 5/8" (41mm) and for the 4" the ID is 2 3/8" (61mm). At least according to my measurements.:blah:

So...:doh:...maybe you could try making little funnels out of sheet material (anything that is stiff and won't burn too quick is fine to play with, right:), with one end matching the 41mm, fitting onto your inner mounting plate, and the other ID (pointing towards the innards of the silencer) changing as needed to get the sound down to not too much louder than stock with the 8 discs. Then you can tune with the discs. Make sense?

The stock ID is 23mm (again I just measured mine). The FMF, both Q4 and PB, are 37mm. I suspect the right size is somewhere in between:) My guess is below 30mm ID. So maybe a funnel 41mm ID on one end, 30mm ID on the other, and 3" (75mm) long? The stock tube goes in 3", so it could be a good place to start:)

I have ST part numbers #444-2003 (4" "disc only" exhaust) and 344-2005 (3" version) and a shield for the 4". Pics below. Just say "Yes", and I'll get them headed your way for experimentation. I don't see how I can connect the 4" cleanly, so I hope you'll give it a shot with your greater skills.

The last pic is for comparison with the end of the stock exhaust with the end cap / SA out. The ST acts as a SA (USFS approved):D

if you can work something out, I'll have to sand, polish and seal my exhaust to match the ST:) Would look mighty nice!👍

Anybody else see any promise in this?

Cheers!/dh

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The 4" would need the base plate that bolts where it the existing sa bolts. In the third picture you can see where they are sunk below where the discs are placed. That would be the easy part because the heads could stick up above the plate and not interfere with the discs. That is why I could make it a lot lighter. You would need some substance around the outside but about 3/8" to safely hold the threads, but the ring could be just a little wider than the threads. Send the stuff and I will whip something up.

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BSS, thank you sir, I'll PM you when it's in the mail.👍

It's not always clear what I personally have in mind:), so I'll try to write it down:

"Give interested owners an exhaust alternative which:

- keeps a USFS-approved spark arrestor

- keeps the catalytic converter

- keeps the ability to be at street-legal dB level if the owner desires

- provides a way to trade sound level for "performance" in small increments

- provides a way to tune the exhaust to other mods

- way cheaper to do than the favorite aftermarket exhausts (to encourage people to try it)

- looks OK (I've learned from the sheepskin:D)"

I don't want to sell anything to anybody. No secret sauce.

I could also keep the EXUP if wanted with this setup. I think time will prove it is worthwhile at low & mid rpms, as dave_in_michigan has already observed.

I'm not interested in welding / cutting the stock exhaust since that might suit me, but not many other people would do that or have it done. It has to bolt on to be interesting.

I hope that blueshopsuper can come out "weight neutral", so that the weight added is offset by the stock weight removed. BSS, you listening?:worthy:

Also, a personal observation: I wouldn't be messing with those 6 bolts on the 4" that hold the disc stack together every weekend. It's too much hassle. It would be fine for tuning and then leaving alone. So either a 3" "one bolt" set-up or some more convenient way to swap 4" set-ups would be needed for people who wanted to have "one for street, one for offroad", or whatever drove them to change frequently.

Cheers!/dh

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