• Don't overlook our Welcome Package, it contains many links to important and helpful information about functions at VHT like posting pictures and sending PMs (private messages), as well as finding the parts you need.


Which muffler will make my CM400 sound more like a vintage Triumph 500?


Aug 20, 2022
Total Posts
Total likes
My CM400 is running great but I want it to sound better. It has 2 into 1 pipes capped with a larger Super Trapp (3" input diameter, with an adapter down to 2") but it sounds like 4-cylinder sport bike--a "zoomy" sound that blends the individual exhaust notes into one syrupy-smooth sound.

In my youth I knew a Gary Myers, whose dad owned the Fay Myers Triumph dealership in Denver. Gary built his own bikes in the dealership shop (from the age of 12 or 13) and became a great rider. At 16, he was the Colorado motocross champ (not called motocross in the 60's) and he owned a totally pumped 500cc triumph, with two reverse-coned megaphones and dual carbs.

That bike is still the soundtrack of my dreams, but I am willing to settle for something that sounds nearly the same on my cm400. I am thinking I should go back to two pipes as a first step, but don't know which mufflers or reverse-coned megaphones would sound most like a vintage Triumph.

What do you recommend that will give something close to that Triumph sound?

PS, Another 16-year-old neighbor owned a brand new Triumph 21 (350cc). After riding Triumph cubs, that bike was silky smooth--almost too smooth, and I still like the bathtub rear fender. A beautiful bike, which we rarely see these days.

PPS, I just discovered a YouTube channel created by a guy who knows more about cycles than anyone I have met--in 70+ years. It is the Bart channel. Bart documents the greatest, rarest bikes and races of the last 50 years, including a world-champion bike that I got to sit on secretly years ago (a huge deal for me!).

It was the Honda RC166; a 6-cylinder 250cc four-stroke GP racer. It was in Honda's US headquarters in Torrance, CA in 1972. I was working there as an electrical engineer when I discovered that their "secret room." One day when no one was around, I snuck into it and found mostly bikes from other manufacturers, which were --allegedly--on their way to Japan to have their better ideas copied.

The RC166 was built like an airplane--with safety wiring on almost every bolt and built with only the lightest parts and materials, since every pound counted. Looking at the cylinders, the pistons must have been about the size of small marshmallows!

Bart accurately described and confirmed my first-hand knowledge about this bike, and added a lot of in-depth knowledge about its amazing pedigree and racing history, including how it finally beat the pesky, world-beating 2-stroke bikes, which out-powered the 4-strokes by delivering power on every down-stroke. The RC166 finally beat them by revving to nearly twice the 2-strokes' RPM, about 21,000.

Bart is one great Channel!! Check it out when you have a lot of time, as it has hundreds of videos with some very interesting knowledge of cycles, cycling, and the world-wide cycling industry. :--)
Moved to SOHC Exhaust section
The blending of the exhaust notes per se is due to the power chamber where both primary pipes dump into and the exhaust leaves thru both mufflers somewhat equally. The Triumphs used single pipes/mufflers per side and sometimes had a balance pipe added towards the head.
People have used take off HD Sportster mufflers successfully to change the sound note lower.
I started running my CM450 with a full-up Power Chamber (center muffler) and completely empty trumpet mufflers (courtesy of the Previous Owner), and the staccato sound of individual cylinders firing was quite clear (and loud). Your 2-into-1 must be muffling a good deal.

I brought the volume down with a screw-on baffle in the front of each trumpet, another baffle in the rear, and stainless steel pot scrubbers in between. The end result is tolerable, just a little loud, but I don't know if I would call it enjoyable, or if it would meet your needs. Ideally I'd like to have shiny new, longer mufflers, maybe pea-shooters, mounted level instead of upswept. What I have is good enough for now.

Here's my post on this, showing you some options in case your next muffler or mod is too loud.

Guys, I thank you very much for your inputs about the mufflers.
I will go see what options I may find at the local salvage yard.
Thanks again!
Top Bottom