i gots a supertrapp exhaust.

[bairdco]

the c(r)ap fell off the end of my pipe for the last time on saturday, and it took the welded hunk of metal with the threads with it, so i couldn't put it back on.

so i ordered a supertrapp 2" i.d. "disc only" muffler from Summit Racing for 50 bucks.

i took the three little baffles out of the inside of the pipe with a beat-up screwdriver as a punch and a hammer, to knock out the spot welds.

so i have an open exhaust, except for the catalytic converter, which looks like corrugated cardboard if you shine a flashlight in there.

the Supertrapp is a 12 disc, tunable muffler that clamps on with a hose clamp (a nice beefy one, too.)

it's not specifically designed for a 2 stroke, so i ran it today with 6 discs. the more discs, the more free-flowing and louder it is, the less discs, the more restrictive and quieter.

it sounded like a quiet dirt bike, which basically means it sounded like a loud china doll.

i went down to 5 discs, but haven't tested it out yet. these mufflers are tunable in all sorts of ways, so i'm gonna be playing with it for awhile.

also got some header wrap, so as i type this, my fingers are all itchy 'cause it's fiberglass. it's also kinda ugly.

and yeah, i could just get an expansion chamber, but that's sooo 2009. i wanna try something different.

[bairdco]

ok, just go back from another run. i went down to 5 discs.

when i put it on this morning, i ran 6 discs, and rode it about 20 miles to get the header wrap and back. there was a noticeable decrease in low end torque, and top end seemed fast, but not really any faster than it used to go, and it seemed to cut out a little, but that mighta been because it made a lot more noise, so it just sounded weird.

i went down to 5 discs, which would give me more backpressure, richen it up a little, and quiet it down.

it pretty much did all that. got my low end torque back, and it's pretty smooth all through the RPM range. definitely not as loud, but more of a throaty sound, instead of the normal "ting ting ting" rattle.

the header wrap smokes for 30 or 45 minutes as the crap in it burns off, and man, it stinks. plus, it makes it look like your bike's on fire.

i'm pretty happy with the way it's running now, it's definitely faster, plug looks great, but i'm gonna take out another disc tomorrow and see if anything changes. i'll probably take out one at a time, just to see what it does.

ideally, i'd like to balance the power with the noise. the noise now isn't bad, but it'd be great to silence it as much as possible, without losing performance.

it also wouldn't be hard to make a home-built disc exhaust outta pipes and some thin steel, so this is a cool experiment with what can be done to a stock exhaust.

[stv1jzgte]

Inspires me to get off my ass and wrap my (old school expansion chamber) with the thermotec wrap thats been waiting for me, though with gloves! did you wet the stuff first? says it helps

[BarelyAWake]

Supertrapps are ossum I usta run 'em on all my dirtbikes, even a streetbike or two (never as small an engine as a HT tho), o'course itsa heck of a lot easier to get them dialed in w/a dyno but still - they rock

I'm not sure but I think they're still the only truly tunable silencer out there o_O

[silverbear]

OK Bairdco,
This looks like a winner. Now we want to see the one you make yourself out of a discarded_______(fill in the blank) and removable discs cut from _________, which only costs $5.38 not counting the clamp. What if the stock muffler were cut in half midway and somehow or other bolts were run fore and aft so that the discs and little spacers(washers?) could go between the two sections of muffler? Could that work or am I not understanding something about the supertrap and how it is designed. What do you think, Barely? I love stuff we can make ourselves. Such fun! Good one, Bairdco!
SB

[BarelyAWake]

I think it'd be kinda hard to beat the simplicity of the Trapp's design and the "disks" do need to be open as that's where the exhaust gasses escape...

But if anyone can make it outa random bits o'stuff kickin' around - it'd be bairdco FTW

[silverbear]

True, it would be simple especially if I had $50.00 to plunk down on one, but I don't so I starts ta thinkin' ya know and I already have a couple ideas. Bairdco, what's that thing look like inside? The discs must be like donuts in having an open center. Then the gas makes it's exit out the space between the discs, right? And you adjust how much escapes by how many discs are in place. More discs equals more free flow, fewer discs means more back pressure. Is there anything else in there?
SB

[Drewd]

You are better off with a tuned pipe. Superetrap are pretty decent 4 stroke exhausts. I had one 25 years go on my highschool bike and had 20 discs on it. Police couldn't do anything about my nosey neighbor's noise complaints because it was not an open exhaust. I ticked my neighbor because I had to make multiple red line runs to jet the carb for the intake and exhaust.

[Venice Motor Bikes]

I know Baird says "expansion chambers are sooo 2009"... But the SBP chamber is pretty quiet & flows real good!

[bairdco]

stv1jzgte, the directions said not to get the black or copper stuff wet, only the natural white, so i wrapped it dry. i had to do it a coupla times to get it right and wrinkle-free, and i made my own clamps out of aluminum. it's a little fuzzy and kinda ugly, but it works really good. i always had a shoe melting problem with the backwards engine set up.

as far as making a tunable muffler yourself, it could be done pretty easily. you could copy the discs using sheetmetal or aluminum or something, take the end cap off the stock exhaust and put a stud in that hole, put the discs in and use your stock end cap with the pipe cut out of it.

that's an experiment for another time, though.

i was joking about the expansion chambers. i'd have to heavily modify an SBP pipe for the backwards motor or get one custom made or something. i don't think i could find one to bolt right on.

and as far as this bike's concerned, i'm at the limits of power. i could make the engine go faster, but it's getting scary. there's not enough fork rake and the geometry of the 24"er just isn't suited for the speeds i'm going. at top speed, it feels like it's floating, the front end get's really twitchy and light. any little bump and it hops around.

i need to build a 26" with better geometry for the speeds i'm planning to go.

oh, and Drewed, it is a "tuned pipe." says so right on the box...