I have seen the $80 ebay endcap and read some threads about DIY endcaps. I took a little different route. I wish I would have taken pics while I was cutting things up, but all I have is the final product.

I found a stainless endcap for a FMF muffler on Ebay for $17 shipped. I wanted a 2" single opening and the outer diameter to be no more than 3" so it would fit up to the stock DS end cap. I got a 2nd endcap with my bike when I bought it as a spare, which makes me feel better than I have a stocker to go back to if needed.

I wanted to keep the spark arrestor to at least stay legal that way, even though I know it won't make the DB requirement. I did all my cutting from the "outside" side of the cap. 1st cut was to get both downtubes as flush to the endcap face as possible. I then took some heavy duty cutting disks in my Dremel to carefully cut around where the pipes were still welded to the cap, so that the two innner tubes would then drop out. I was left with an oblong hole the cap, and a complete spark arrestor but nothing else. I had to massage the hole in the cap until the backtube in the FMF cap would drop down into it. I then lined up the FMF cap, marked and drilled holes to use .125 aluminum rivets. I packed the backside of the FMF cap with high temp silicone so that it would be completely sealed against the DS endcap. Line the two pieces up, rivet them together, clean up an silicone, and hit it with some stainless polish to shine it up a bit. It's not the best looking endcap I've seen, but for around $20, and some of my time, I'm happy with it. I jetted up from a 165 to a 170, but after taking the 1st ride with the endcap today tells me I need to go up even further, possibly to 175. It sounds much deeper in tone, and louder than before, and the difference in the exhaust pressure coming out of the pipes is much greater.

You can also see the 30cal ammo can that I'm using for storage that is tucked into the 6-pack rack. It's an interference fit, but I like that so the can won't rattle around. I keep some tools, a hand air pump, 1st aid kit, electrical and duct tape, etc... in the water resistant can. It has a nice rubber o-ring all around the inside of the lid of the ammo can and the latch snaps closed firmly. I picked up the ammo can at a military surplus store for $12.

 

Nice looking end product. So the screen is still intact correct? If so make sure you keep an eye on it because along with the increased air flow out the screen will catch more of the packing and might burn a hole in it over time.
With a 730 and a Lectron 48 and ported head I actually burned two different screens out of a Yoshimura RS-3 exhaust. Fortunately I ride primarily dunes so it's not much of an issue, but just keep an eye out since you're flowing more air.

 

Ace, the cap does have the complete screen still intact. Are you suggesting that you have had packing lodge itself up against the screen and that the packing will then burn over time, and consequently burn the screen in that area as well?

 

It has happened to me like that. Not sure if it was something out of the ordinary or not but I'm thinking that they sell muffler packing and replacement screens for a reason.

 

Bought some FMF packing, and repacked the muffler this weekend. There was a 3-4 in section of the muffler that did not even have packing around it. Needless to say, it sounds deep and throaty now, but not abusive to the ears. I put a 175 jet in and adjusted the air speed screw. Took it out and did some runs ina awash and hill climbs, and I can totally tell a difference in the power. There is a sandy hill I climb that I used to feel like I had to have pretty fast forward momentium on to get over it, but this time I was going slower and had lots of power to spare. There are walls only 6 feet apart for most of the hill, and the exhaust sounds awsome as I powered up it.

Getting an open end cap, Uni filter with no air box, along with the correct jet size, and the OMR carb mods has totally made a difference in the way the Bomb feels now. I still have a 15 tooth primary sproket to put on, so that should wake it up even more.

 

theres nice billet end caps on ebay right now