....You will need a nice scrap of 1.5" diameter tailpipe about a foot long with a curve in the end, welding equipment and the ability to use them. You can Oxy-Acetylene the whole thing or use cutting tools and a MIG. Whatever you're good with.

....... I kept the spark arrestor as it is except for squaring the metal inside end cap with a big hammer. This allows for a little more flow around it, the oblong shape to accomadate twin pipes no longer neccessary.

.....The tailpiece I selected from my scrapheap had a nice curve in it already, so I trimmed it off for a nice exit position. It goes into the spark arrestor to within about an inch of the inside end cap where it is necked down to a smaller hole about 1" diameter. Then I cut a bunch of slots with a cut-off saw in the sides. Make this piece before welding it into the end cap itself, it will look kinda like a really nasty dildo about 10" long. Remove the gasket on the endcap before any welding or cutting, I didn't, and fried it real good. A cutting torch worked well for removing the old twin tailpipes, but it also blew through the spark arrestor screen in a couple of places so be carefull, or try something else.

....Filling the holes from the twin tailpipes in the endcap around the new larger single tailpipe is pretty easy. I have done this twice now, once filling the holes with weld, once with some little scraps of metal, either works just fine.

.....I am running a 175 mainjet, but might be just a little rich. 170 would probably work better. 165 was stock. The Dynojet needle was worthless, tried it again and again. Just buy a couple of mainjets and allen screws for the float bowl
and save a bunch of money.

.........It is quieter than any slip-on, yet has a definite power increase, and the price is right.

........Use the money saved by this project to buy a CDI from Knutz.
Doing jet runs with the stock CDI and hitting the rev limiter every time sucks.

How loud is it?

It is noticably louder than stock, I'll guess 95 decibels, if stock is 93 decibels, but not so loud that I feel uncomfortable riding up the road to the local store in front of my neighbors. I could NOT ride around here with a slip-on without getting some crap from some neighbor, which I put at about 100 decibels. These are just guesses but the proportions are about right. 93db stock, 95 modified end cap, 100 slip-on, 106db open pipe. [img]i/expressions/face-icon-small-wink.gif[/img]

Well I think I'll just make a few of these and see how they do. I've had private e-mail on this asking if I could and would, and why not?
I have improved my technique in making these and can save nearly all the chrome, except right in the weld area. They are so much quieter than a slip-on, have nearly the same punch and are cheap to modify. It is certainly cheaper to modify than to make a whole new end cap.
......So anybody want to sell me some stock end-caps? I will need a few to perfect my technique and be able to exhange "cores" for a quick turn around. How about $20 for the first 5? Or send me your end cap and I will return it with the final version for you to test, after I have tested it, for free. Once again, first five only please.

......I will be dyno testing and decibel testing on my DS, which is stock except for a Pami CDI, and end cap, 175 mainjet. I should sell it as a kit with two mainjets, and four allen head carb bowl screws.
......This could be fun, and make a little Christmas money, well maybe for next Christmas eh? I can get some prototypes out before this Christmas.
I've done this and it works, I just need to slick up my process.
[img]i/expressions/face-icon-small-cool.gif[/img]
.....Knutz is working on whole new end caps, for a bunch more money. This is kinda like recycling, making a cool new part out of a funky stock part and being able to use the stock muffler to boot.
I think there's room for both.

I guess that means that you will not be sending me yours for dyno testing and compairison then fourlix.

It's not really fair to say a bunch more money, since I haven't set a price yet. What is your price going to be anyway?

One advantage to starting with a new cap, you can always go back to stock if you don't like the modded one, or if your riding in an area that you need it really quiet. 4 simple screws and your back in hush mode.

I guess next time I won't do any R&D to ensure I get the best design for flow and noise, I'll just get it on the market befor someone else does. LOL J/K

Fourlix~
You definitely need to get a digital camera!!!LOL Where is the power increase most noticeable? I am looking for a better low end punch from my DS since the stock machine is pretty weak taking off. I would definitely consider buying an endcap for around 50 bucks or less.

Knutz~
I try to think of myself as an average guy. I have been keeping an eye on posts from you about the endcap. I would have a hard time justifying spending $100 on an endcap when i could get a new slip on for around 200 dollars. For the extra hundred bucks, I would be getting a whole new muffler, better appearance, and most likely better performance. Maybe some people will value saving a hundred bucks and being able to carry their stock end cap with them. I realize you are building these from scratch and you have to make some profit for the business, and you don't have a final price yet, but maybe a slip on would be more profiteable than just an endcap. Do you think a slip on could be built and sold for aroune $200? You are a very reputable rotax engine builder so I truly think people would look at your product if the price were comparable. Right now, the only comparable endcap is the pingry's which retailed for $69 I believe. Although cheaply built, it is something to be used as a comparison. I am speculating your end cap would cost more than that from what I have read. I hope you don't take this as an insult because I didn't intend for it to be that, just some feedback from what I think is a "normal" ATV rider.

.....Well I don't want to piss off Knutz, I will probably only make a few of these anyway. There are certainly advantages to having a totally new end cap and keeping the stocker for quiet time. My design is untested dyno wise, and the sound level is probably more than the Oregon laws allow, I would think anything other than stock just isn't going to work there.
......I also think rebuilding end caps on an exchange or core type basis
is awkward compared to merely sending out a new product, which I am not prepared to make. It's the cap part itself which is difficult to come up with. The stock piece is stamped out, fabricating one would be difficult, which is probably where Knutz is.
......But I am willing to make a few of these and haul my DS down to Phoenix for some Dyno and decibel testing. I think the DS muffler is pretty cool, especially inside, and if I can make a few of these and make a little Christmas money in the process, what the hey. I was going to be paying for my own dyno time with Knutz anyway, and I will still let him check it out, if he likes it better than what he's already got, maybe we can work something out. As I said, there is room for both an aftermarket end cap and a modified end cap.
....... I am very noise conscious, but would not go back to the stock end cap even if I had one, if for no other reason than rejetting is a pain.
........There aren't that many DS's out there and Knutz is doing us all a great service providing the parts and expertise to take it to the next levels. But there is room for a cheap quick fix here and there too. Not everything needs to cost an arm and a leg, and I think I can make this worth my while for about $45.
.......Now if there are some of you with abandoned stock mufflers lying around the garage because you've replaced it with a nice shiny loud aftermarket pipe, consider selling me your endcap for $20 or lending it to me for some R&D. I'll return it to you in a couple of months, modified for free, after I'm done testing it. There may even be a extra internal baffle, removable, for the Oregon guys. But Dyno and decibel testing have got to happen before anybody pays anything. And I only need a few end caps to work with. [img]i/expressions/face-icon-small-cool.gif[/img]

sorry double post

Fourlix~
I have picked up a used DS exhaust system for 20 bucks and will have an extra endcap laying around. I am going to give your endcap mods a try. Just a couple questions. Would brazing be strong enough to hold the tail pipe on? What effect would using a larger or smaller tail pipe have on performance and sound? Thanks.

I think a larger end piece is a good idea. I think the 1&3/4" or even 2" might be the way to go. One of these days Knutz will be dyno testing the assortment of endcaps he has, two of which are mine. Hopefully we will know more than we know now, which is just seat of the pants, and eardrum pressure.
Unlike the Texas guys, I wanted my end cap to be quieter than a slip-on. My first one used the stock spark arrestor with a 1&1/2" tailpipe. My second one used 1&3/4" pipe, a reverse cone, no spark arrestor and a lot of slots. I am going to post some pics of it.[img]i/expressions/face-icon-small-cool.gif[/img]

DS Modified end cap, 1&3/4" with reverse cone, quiet version