Triangle Muffler Opinions

[vintagenut]

Hello All,

I'm hoping for some suggestions on how to proceed with the exhaust on my latest project...

I'm presently in the midst of an early M80 Sherpa T rebuild and am striving for original appearance yet with increased performance in the effort.  I had one of these years ago and, like many, replaced the triangular muffler with an "S" pipe to a modern aftermarket spark arrestor which did perform better than stock but, to my eye, didn't look nearly as good - certainly not period correct, anyway. I eventually sold her to a friend to entice him into riding vintage trials with me and have missed the bike ever since.  Such a beautiful tank design - truly a classic.

Anyway, I found another m80 - mostly in parts - but thankfully came with some extras including two triangle mufflers.  So... desiring a quieter, less restrictive muffler, I decided to open one of them up to have a look inside and modify.  Which brings me to my question...

Now knowing for sure the internal layout of this box, how would you suggest I proceed?

Remove the internal baffles and connect the inlet/outlet with a perforated tube and surround with heavy packing? What do you think of replacing the existing outlet tube with one of a larger diameter for even less restriction?  Or instead maybe adding a second outlet tube of the same diameter below the first, similarly connected?  A twin exhaust might be kind of fun. 

Additionally, I may slim the unit down somewhat while I have it apart. With the internal baffles removed, there's really no need for the housing to be quite as deep.  Nothing too drastic... just enough to tuck it in a bit further.  I've already repacked the mid-box so I hope, once done, she'll flow more freely and run more quietly than the day she rolled out of the factory.

Your thoughts would be greatly appreciated!

Best regards,

Christian

 

 

 

 

[pschrauber]

I would enhance diameter of the tube to around 25 - 30mm, then a holetube connection between them, then I would fill up with void with insulation for two stroke exhaust.

Close the box again but as such that it is easy to take apart for cleaning and replace the insulation.

Then you should have a bit better performance without more noise, much more effect would have a bigger exhaust volume in general.. 

[sherpa325]

The M80 wouldn't look too bad with the later 'boomerang' or 'clubfoot' - which both perform better than the original triangular one. I don't recall anyone using the original back in the day or even now but that is not to say it couldn't be modified to give a nice note and decent performance, however the volume looks to be way smaller than the current setups and it is impossible to make it bigger. I guess you could try opening up all the baffles as well as using larger diameter inlet and exit tubes as has been suggested.

[woody]

I have a triangle on my M49. It's an aftermarket Spanish one from In Motion, it quietens the bike down nicely and no loss of performance at all. It could be that there are no baffles in it, I don't know, but the bike runs fine with it fitted.

[vintagenut]

Thank you for your input!

You know... I seem to have a little issue with being penny wise and pound (dollar) foolish when it comes to these old bikes.  Woody, I could (should?) have purchased a new triangular muffler as, I've heard, they do perform better than the OEM mufflers... but I balked at the price for some reason.  I'm sure I'll wind up spending lots of time, effort and money modifying the one I have, likely exceed the cost of the one I balked at and STILL find it too restrictive!  This, of course, is not too unlike my history of passing on a perfectly good, ready-to-ride (but expensive) motorcycles... but will excitedly buy a "deal" at half the price and restore it for significantly more than I would have if I'd just purchased one ready to go!  Maybe it's the challenge of it all... ego, maybe?  I don't know.  Thankfully the fun factor remains quite high which, I suppose, you can't really put a price on!

PSchauber and Sherpa325 - yes, I think enlarging the inlet/outlets as well as the exit tube of the midbox itself should do the trick.  I've entirely removed the baffles (THAT was fun) and am now looking for a sensible method of connecting the two with some perforated tubing.  And yes - I LOVE the idea of making it repackable.  That would be fantastic!  I'll let you know what happens and will definitely post pictures of the finished work once it's complete. Fingers crossed it should work out quite well once done.

Thanks again and best regards -

 

 

 

 

 

 

 

[Antonio]

On 10/1/2019 at 10:10 AM, woody said:

I have a triangle on my M49. It's an aftermarket Spanish one from In Motion, it quietens the bike down nicely and no loss of performance at all. It could be that there are no baffles in it, I don't know, but the bike runs fine with it fitted.

De

[vintagenut]

Hey all -

Just a quick update on the silencer mod.

After a thorough cleaning and the removal of all baffles, I trimmed approximately 10mm in depth from the box to slightly reduce heel or tire contact contact (depending on how it's mounted at the tab) and took it to a good friend who tied the inlet/outlets together with some perf tubing.  The challenge, he told me, was in making the very short 90 degree tubes you see connecting the perforated section.  He made a die to stamp some sheet metal (as one might when building an exhaust pipe) into 90 degree halves, then welded them together to create the new pieces. The box has since been tightly packed and welded back together.  I'll attach further photos of the completed mod soon.

Regards -

Christian

[section swept]

Heres my M80 with later rear box

[vintagenut]

Hi Section -

That does look nice -  thank you for the photo! 

I see you drilled the frame loop gusset as an attachment point, added an extension and moved the muffler tab to fall in line with the frame mount.  Very clean approach and easy to revert back to stock if desired.  Question... did you need to adapt at the muffler inlet (shorten or shim) to accommodate the tiny mid-box outlet?  Overall the minimal effort it would take to make it fit would be worth it if it quiets the bike without compromising performance.  

Thanks again for the suggestion. If my little experiment doesn't work as hoped, I'll definitely try your approach next!

Cheers -

Christian

 

 

 

[section swept]

On 11/2/2019 at 3:43 PM, vintagenut said:

Hi Section -

That does look nice -  thank you for the photo! 

I see you drilled the frame loop gusset as an attachment point, added an extension and moved the muffler tab to fall in line with the frame mount.  Very clean approach and easy to revert back to stock if desired.  Question... did you need to adapt at the muffler inlet (shorten or shim) to accommodate the tiny mid-box outlet?  Overall the minimal effort it would take to make it fit would be worth it if it quiets the bike without compromising performance.  

Thanks again for the suggestion. If my little experiment doesn't work as hoped, I'll definitely try your approach next!

Cheers -

Christian

 

 

 

Sorry for the late response. No mods to clearance, although the suspension is close it does have clearance...about 1/8th of an inch. The drop bracket is a piece from a Scotoiler Kit?. The connection from mid to tailbox is unmodified save for a new rubber O ring seal.?

[onthegas]

I also replaced the triangle on my M98 Alpina with the later banana-style silencer and welded a tab onto the rear fender loop.

My next project is to open up, clean and re-pack the mid box.

[vintagenut]

On 11/12/2019 at 1:34 PM, section swept said:

Sorry for the late response. No mods to clearance, although the suspension is close it does have clearance...about 1/8th of an inch. The drop bracket is a piece from a Scotoiler Kit?. The connection from mid to tailbox is unmodified save for a new rubber O ring seal.?

Thank you for that, Section - much appreciated.  I have to admit some ignorance, though...  when you say Scotoiler are you talking about the chain oiling system?  If so, I commend you on your resourcefulness!  Whenever I'm in need of a bracket or other immediately unavailable piece, there's nothing within sight that's safe from scavenging. It does make for some good storytelling later, though!

 

3 hours ago, onthegas said:

I also replaced the triangle on my M98 Alpina with the later banana-style silencer and welded a tab onto the rear fender loop.

My next project is to open up, clean and re-pack the mid box.

Hey there, OTG - another nice example of a banana silencer - thank you for posting this!  I do like the lines of this silencer on the slimline bikes, I have to say.  Just looks... right.  I pulled the clubfoot from my 199a just to size it up before the big disassembly and thought it a bit bulky to my eye.  Probably performs a bit better sound-wise than the banana-style but I do like how sleek the banana looks and how well it blends with the lines of the slimline tank.  Aesthetically it just seems to flow...  So nice to have some good options!

I'm attaching a couple of photos of the finished triangle muffler (minus paint and chrome shield for the moment) along with a couple pics of other efforts on this project.  She's a little skinnier in depth than before (by 10mm) but otherwise nicely packed and ready for finishing.

The shot of the muffler is a re-pack approach my friend suggested we try just for simplicity. As this will be as much a rider as a "restoration", I agreed. So he cut a port to stuff the packing through (and he packed a lot!) rather than a complete separation of the two halves.  I'm still some ways away from testing this but will let you know how well (or poorly) this attempt works when I do.  BTW... clean those exhaust parts really well before welding. It'll make all the difference when you try putting everything back together.  We tried some welding on an a damabed m49 mid box that was destined for landfill and burned a couple of holes right into it when we attempted repair.  Lesson learned...

As to the pics of my cases... as my m80 is an earlier model and uses the single seal main seal holders, I thought I'd try an upgrade to the later, deeper holders that accommodate a pair of seals per side... and had my friend add some o-ring grooves for added sealing.  Overkill, I know... but I thought I might as well try while it still in a million pieces than regret not doing so once assembled.  Hindsight kinda sucks that way...

Thanks again for the photos and advice - very inspirational and truly appreciated!

 

 

 

 

 

 

[onthegas]

Thanks VN! Nice looking job on the triangle silencer and mid-box.

The inlet pipe on my stock triangle silencer broke away from the main body. When I went to repair it I looked inside with a borescope and found it completely full of carbon, worse than yours. The bike was just too loud without a secondary silencer so I looked for a clubfoot silencer since it is stamped as a spark arrestor needed for riding on public land. Even the used ones on e-Bay were quite pricey, but I found the banana silencer for $50. I did have to make a bushing to reduce the size of the inlet and fit the outlet on the mid-box. Sound-wise the bike is a bit quieter, but the biggest change I've noticed is in throttle response. I've also got a spark arrestor tip I can add to the end of the silencer. I'm going to modify the mid-box so I can easily open it up and repack it again. When I bought the bike it had an old Pirelli knobby tire on the rear that was too wide. The tire rubbed a small hole through the back corner of the mid-box which will need repair too.

Although my bike is an M98 (175) Alpina, it had a 250 top end when I bought it, but didn't have the correct tank and seat. I added the Sherpa-T slimline tank and seat along with low front fender brackets, plastic fenders, trials bars with risers and trials tires. Later someone gave me a basket case M91 that had been in a fire. I managed to salvage the primary drive and transmission gears which were swapped into the M98 cases. The only other changes I've made were adding a Mikuni VM26 carburetor and a Domino trials throttle. If you put my M98 alongside the M80 they look virtually identical.

[vintagenut]

Hi OTG,

I'd never have guessed your bike is an Alpina. She looks great! - and in every way a Sherpa T from what you describe.  The frames from this period were identical along with most of the common parts...  and, with the the added transmission from the m91, it's all T with Alpina serial numbers.  It sounds like you've got her nicely dialed in, too.  Good job!

I was going to go down a similar path of converting a running m85 Alpina I came across but ended up moving her along when I picked up the non-running (and very neglected) m80.  The Alpina was very original, rode nicely on the trail and likely could've done well at vintage trials but I didn't have the heart to mess with it and was swayed by the nostalgia of having another m80 like the one I originally owned. The buyer fell in love with the bike and, for a change, I didn't lose any money in the process... unless you factor in the time and effort it took to make it run well, that is.  Then maybe I'd say I broke even.  Maybe.

Hey - when you get to the point of repacking your mid box, please post some pics and info on your effort, will you?  I'm very interested in seeing your approach to a re-packable mid box.  I don't know how quickly muffler packing degrades but I'd imagine after a couple seasons of regular riding, another re-pack would do the bike wonders.  Having it set up for easy access would be fantastic.  Hope to see!

Cheers -

 

 

 

 

[onthegas]

Will do on the photos VN.

I just finished building an exhaust for my son's 74 TL125. That project started when we decided to replace the worn out stock shocks with a set of rebuildable Showa shocks off a Honda MR175. The shocks were larger in diameter and wouldn't fit with the stock TL triangular mid-box. So I built a new swan-neck piece and connected it to a small muffler that came off a log-splitter engine. Along the way I discovered the flange on the head-pipe was rotted out, so I had to fix that. Then I decided to make a whole new, re-packable, silencer from a bunch of scrap I had laying around. I can add the same spark arrestor tip that I have for my Bultaco. It's not whisper quiet like the stock TL exhaust, but my son enjoys the slight performance increase.