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.  But they are rather loud even with a baffle installed.  It's a popular exhaust on some Kawasaki, like my Vulcan S 650 (bought last October).

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

I’ve watched a lot of videos and done a lot of reading over the last month including David Vizard.

The topic of back pressure and scavenging is endless.  I think what I’ve learned is (y’all please correct me if I’m wrong):

1) Back pressure is never good.  It hinders most important flow.
2) Scavenging is always good even if there is no valve overlap (it doesn’t ever hurt anything if it’s sucking on closed exhaust valves).
3) Reversion is the opposite of scavenging and just plain nasty.
4) Exhaust velocity is the friend of scavenging but give up some flow to achieve it.

#4 is where we all get stuck.  It creates the ‘myth’ that you need some back pressure to have scavenging.

I love David Vizard’s exhaust system design.  DBM touched on it.  I think of the ‘resonator’ as an ‘expansion chamber’ that became the Holy Grail on 2-stroke exhaust systems.  

Vizard solved the riddle - “How can I put a big sucking negative pressure wave on the tail end side of the positive exhaust pulse without adding back pressure and hindering flow?”

Motorcycles make things more difficult - we just don’t have much space for all this good stuff.

I’m trying to work through my own dilemma with a recently installed aftermarket exhaust for my bike.  The beautifully designed stock system is a 2 into 1 with 28mm ID (1.1”) primary headers.  The aftermarket system I have installed is a true dual 2 into 2 with 34.7mm (1.37”)  ID primary headers pipes that “step up” to 45mm (1.75”) for the last 8-10” of the pipes until they meet muffler inlet.  I’ve lost a little responsiveness in the low/mid rpm range with the wider diameter headers.  Not much but I can notice it a bit.  The bike screams power in the upper rpm range!  As DBM proved with his hotrod, there is such a thing as “too big”.

But I want my cake and eat it too!

Maybe you just want to go back to the quiet stock exhaust.  I don’t think you’ll find an aftermarket  ‘off the shelf’ muffler that will be particularly quite.

I may be headed back to the stock exhaust myself, but I’m going to try some baffles at the muffler outlets first.  Will I be installing too much back pressure?  Will the location of the baffles put the negative pressure wave in the right time and place?  Things I don’t know.  About the best I can do is test it with some elapsed time runs through the low/midrange and throttle “feel”.

A lot to take in here, really appreciate everyone's insights.

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Interesting -- so, since you posted this I've continued reading and have found a lot of info corroborating what you are saying here DBM, that inertial scavenging is mainly influenced at the header. The header on a stock savage is quite restrictive (as in small diameter), is that correct? I know I've come across multiple posts of people porting out the header for increased flow (assuming in combination of other mods, for it to make sense), but for my purposes, it sounds like I should switch gears and think about the resonant wave you mentioned.

It seems that the resonant wave is more influenced by muffler set up based on what you are saying, allowing exhaust gasses to turn. From what I've been reading about drag pipe sag or the resonant wave, my current thoughts are that the resonant wave or drag pipe sag disrupts the laminar flow of the exhaust -- you mentioned an abrupt turn to break that wave up, do  you mean a physical turn in the exhaust system or that the gasses turn? basically, drag pipes with a lolipop installed would force gasses to "turn" around the insert, would this break that wave up? Maybe I could just look into this for my purposes.

Also thanks for the video.

Thumper:

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I'm very intrigued by this -- do you know where I can find any info about the amount of valve overlap on this motor? With my limited knowledge I believed all 4 strokes needed valve overlap by virtue of their design.

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To me this sounds correct, but I assume both of us are still learning here.

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Well, it's not so much about the tone/noise, although It IS too loud with my current muffler. I believe I'm leaving low to mid torque on the table due to having this baffle-less straight through, which is what i'm trying to determine -- also after years of abuse my exhaust is in very rough shape, I've got a decent dent right at the bend near the footpeg and intend to replace the header as well as the muffler. Quieter would be pleasant but I'm really more curious to see what low end performance I may be missing.

I think i'm going to read through DBM's shootout -- cherry bomb glasspack is an interesting idea, I think they have some shorty sized ones, I wonder if I could/should throw a lolipop insert into one of those and try it out.

Agree with Fast650 about Mike’s testing and measuring of the valve overlap.  That there is NO valve overlap with the stock cam.  I think you can forget about trying to scavenge any low/midrange power.

The stock header pipe on the Savage is restrictive (narrow diameter) and the exhaust port couldn’t be much more restrictive in terms of flow.  I’ve learned 99% of this from DBM, Fast650, and Dave.  Verslagen, Lancer, and FinnHammer know this all too well themselves.

I think you are experiencing ‘slow under-powered bike syndrome’.  When the bike was new to you, it felt just fine.  Now it seems inadequate and you want more giddy up.

A larger diameter header would probably do more harm than good for low/midrange torque on a stock engine.

The reality is you can’t gain much on the LS650 with baby ‘stage 1’ mods - exhaust, intake, and carb tweaks.  

As I recall, the biggest difference the dyna muffler made was closer to the top of the powerband.  It just seemed more willing.  I don’t remember it doing much for low/midrange (but it sounded better than the whistling stock exhaust).

I know you’ve tinkered some with your Mikuni VM36 carb jetting.  And I know you want (need) a new muffler, but you might try different positions of the clip on the needle.  Try raising the clip and adding a bit more fuel to get more power (or maybe it needs to be leaner - aren’t I helpful, lol).

Personally, a gently used Dyna muffler is pretty nice.  Quality made, nice finish, not too loud, not difficult to install and tune, and good bang for your buck.  But, if it doesn’t fit your eye, then it ain’t the one.