Bought a Supertrapp for my GS400/425/450 MAC exhaust, here is how it went.

[donimo]

Hi, I recently bought a supertrapp muffler off ebay,





I knew that the bracket location was wrong and that it most likely was meant for a car or harley bagger (2" inlet), but it filled 4 very important criteria:

1) 2" to fit my MAC header, but "tunable" so I didn't have to go nuts on carb tuning (pretty much had to be a supertrapp)

2) Under $100 shipped to Canada (xmas cheque my aunt still sends me )

3) glass packed so it's not too crazy loud

4) Under $100 (yes I put that twice)

I needed something because the weird MAC muffler that the kit came with was impossible to tune. It ran very weird, less power off idle, but then decent low-mid, then it would die off, then after about 7000rpm would take off again. I tried jetting up and moving the needle up a step, just got worse. I have very little time these days so I put it back to stock and just kept the revs down for the rest of last summer.

After looking at the muffler guts I think it was actually choking it off as the cross section of the outlet was only an inch or so, but inside it was crimped down to less than half that. Plus it sounded like ASSSSSSS



So I figured I would try a supertrapp and try to get the tune as close as I can with that, then try the carbs.

I soon found out that it is over $250 for a supertrapp in Canada, so I went hunting on Ebay and got that one, but there are MANY other ones with a 2" inlet so buy whichever.

I only just figured out a mounting solution for mine and it aint pretty so I suggest buying a different one if you are going for looks. I will post pics tonight but there is a weld seam the entire length of the bottom and because of the bracket location that is what is facing out when I mount it, ECHHH

I will finish mounting it and do a preliminary start up and post the results some time in the next couple days.

Just thought this might be useful to someone as MAC is the only choice for "off the shelf" exhaust for the little twins and I know at least one other member on here that isn't too happy with the sound or performance.

[donimo]

Anyone had success with grinding down a weld seam and poilishing? It's stainless and I have never done it before.

would it take too much off and weaken the weld too much?

[donimo]

Here are some quick pics with my flash happy camera:




I know that seam is gross, but that is what happens when you buy things based on price and not on other things like asthetics I guess .

I haven't cleaned the bike since putting it away either ha ha

[salty_monk]

Can't you make a bracket to allow you to spin it? Must be possible & would look better than that.

I wouldn't try grinding & polishing....

[donimo]

Can't you make a bracket to allow you to spin it? Must be possible & would look better than that.

I wouldn't try grinding & polishing....

I did that first, I think the bracket welded onto the top looks worse than the seam. At least the way I had it. It is all bolts and brackets and echhh.

I will set it up that way later and take a picture (should have first, duh)

[rudy]

I was looking at those mufflers when I was building the xs400 cafe. I'm curious to see how it runs, and also how it sounds. My xs has straight pipes right now. I don't ride it, so it doesn't much matter that it's loud.

[donimo]

So I got all impulsive and insured the bike, it has been gorgeous for weeks here, 2 weeks of sun and 12-15*C weather is too much for this guy.

Rode a bit last night and again to work this morning.

I would just like to say, in realtion to the tuning issue I had since putting the MAC system on:

SOLVED

The muffler came with 12 discs, I just split the difference and put in 6. It used to have the most screwed up pull from idle to redline, it was weak off idle, then picked up fast, then felt like Axel Foley put a banana in the tail pipe, then it would climb slowly till about 7k then take off like a sexually assaulted primate. I had been told I needed to jet up, tried that, it got worse. I always had my doubts though as 1-3k was ok, the bad until 7k then fine. maybe needle jet, but whatever, solved now.

I will post up a video when I have time to make one, but the sound is great IMO, but that is VERY subjective obviously.

It has a very "burbly" sound on decel, with some nice pops (I always liked the pops). It isn't quiet by any means, but it is very civil if you go easy (prolly due to the glasspack?) and nasty if you open it up. Best I can do is it is very similar to the magnaflow mufflers I had on my mustang.

I am all giddy, first ride of the sease (and WAY early at that) + new muffler fixing old problems =

[donimo]

anybody have any tips, or ideas, or pictures, of a bracket that I could buy/make/copy to mount it right side up? I reall y have to metal fab experience so any help is good help.

[Dave8338]

Though it may be a little more pricy than you would like, IF you could find someone to mill you a simple bracket (or weld one out of aluminum that you could polish) then use some stainless torx or allan bolts, you could make it look VERY nice.

Since it solved the throttle response issues and IS a quality piece, spending a little extra on a good bracket would be well worth it IMHO.

[donimo]

went for a rip at lunch (if I am not supposed to be gone for an hour why do they cal it a "lunch hour"?) MAN does it rip now. I am sure that the bigger bikes pull way harder but the front end lifts (not off the ground ) through 4 gears now, never did that before. The jetting on the top end may be a tiny bit off as it seems to have way more bottom end than top but MAN is it an improvment.

I couldn't stop riding, I went for gas and to deposit a cheque and a 5 min ride turned into an hour and I still didn't want to go back to work,

[donimo]

Though it may be a little more pricy than you would like, IF you could find someone to mill you a simple bracket (or weld one out of aluminum that you could polish) then use some stainless torx or allan bolts, you could make it look VERY nice.

Since it solved the throttle response issues and IS a quality piece, spending a little extra on a good bracket would be well worth it IMHO.

I will inquire at the local motorbike place, there is a guy who works there that is the brother of the local ironworks place too so it should be a place to start.

Don't want to spend too much as the only reason I bought this particulat supertrapp is that is was so much cheaper.

[tkent02]

The jetting on the top end may be a tiny bit off as it seems to have way more bottom end than top but MAN is it an improvment.

You have some carb tuning to do. It should feel like it has at least twice the power on top as it has down low. Should hit about 5,000 or so and take off like a shot.

[donimo]

I re read what I typed and I kinda overstated the effect, it's not all bottom end, it does take off, just seems a bit lower that it should. It goes like stink.

I do need to retune for sure though, just happy to have a solid place to start now, before it was all over the place.

I think I will try the 120 jets I have and go from there, the bottom and mid range are awesome, the top end seems about 80% of where I would expect it. Hard to say with your first bike though eh?

[tkent02]

I re read what I typed and I kinda overstated the effect, it's not all bottom end, it does take off, just seems a bit lower that it should. It goes like stink.

I do need to retune for sure though, just happy to have a solid place to start now, before it was all over the place.

I think I will try the 120 jets I have and go from there, the bottom and mid range are awesome, the top end seems about 80% of where I would expect it. Hard to say with your first bike though eh?

Most newbs completely underestimate the top end capabilities of a small high RPM motorcycle engine, especially one with a pipe.

Get it jetted right before something burns up inside.

[Dave8338]

Most newbs completely underestimate the top end capabilities of a small high RPM motorcycle engine, especially one with a pipe.

Get it jetted right before something burns up inside.

AHHHH...the flywheel effect of minimal displacement!
Let er RIP!