Yo savages!!

I've been running this slash cut, 3" diameter baffle-less straight through the last three years. It's too loud and I believe does not allow efficient scavenging  -- I think I need more restriction for better low end torque.

I know the dyna is often praised on the forums and can be quite cheap to purchase used, but am interested in other suggestions as well. The supertrapp metric megaphones look nice with the modular disks and all, any thoughts about those?

Also, thumper if you read this and still have that old supertrapp for sale I'll purchase that off you.

Thanks all

These Emgo mufflers were used by RYCA on their Cafe' bike kits.

https://www.amazon.com/Sporacingrts-Stainless-Motorcycle-Silencer-Moveable/dp...

They are incredibly loud as delivered - you can find YouTube videos for doing the Crumb Cup modification to reduce the excessive noise.

You can also modify the perforated core by blocking the center pipe and turning it into a baffle (rather than just a perforated pipe where the exhaust blows straight through).  If the exhaust passes out the holes into the area between the core and muffler body then comes back in they muffler muffles more.



Later on they made a replacement baffle that did a better job.

Great suggestions here thanks guys,

Finn that thread on mokes project is amazing, I was actually searching for that before notice you posted it so thank you.

Couple of questions here -- Mike in that thread comments on the back pressure myth. Hopefully Mike can grace us with his presence if interested, I have a lot of questions about this.

As many know "back pressure" is often referred to by people, usually in the context of free flowing straight throughs, that torque can be limited  by not having adequate "back pressure". I believe this to be a misconception, that a free flowing exhaust is always preferable -- however, back pressure and scavenging are different things. If I understand correctly scavenging is the phenomena of increased exhaust gas velocity due to the inertial slug generated by a high pressure environment in the exhaust, typically achieved by in some way limiting flow, like with one of those "lollipop" inserts (washer tac welded to a bolt) or another type of obstruction.

This increased exhaust gas velocity due to obstruction has a positive influence on torque on the low end, however is not desirable with a WOT, which is why some much fancier bikes have those variable exhaust systems, among other such considerations (scavenging is very complex and valve/head design etc are factors in efficient scavenging.)

What are your guys thoughts about this? My inclination is that our big singles  CAN benefit from some obstruction to increase exhaust velocity, but my knowledge is minimal about such things.

Surviving Philly wrote on 06/12/25 at 14:34:56:


No engine likes backpressure. If it runs better with backpressure then you have something way out of whack with the build. Watch David Vizard's videos on youtube about his exhaust and muffler designs. The man designed a muffler that was street legal and made the same power as an open pipe. When it comes to airflow the man is at the top of his field.

Hey Philly!  SuperTrapp is long gone.

On the topic of scavenging, it can only occur when there is valve (camshaft) overlap.  The stock LS650 cam has no valve overlap if I recall correctly.  I beleive the DR650 cam does.  So nothing to really worry about if you have the stock cam.

I'd look at DBM's muffler shootout.  A dressed up Cherry Bomb could be kinda cool.

Delkevic also has a few options.  Kinda pricey.  I haven't heard it on the LS650.  It's a popular exhaust on some Kawasaki.

https://delkevic.com/bull-nose-tip-21-round-stainless-to-fit-s40-boulevard-1986-
2019/