Modified stock muffler on 2011 Sportsman 800

[Thomasj]

I recently bought a HMF Swamp XL exhaust for my 800 and it gave it a huge power boost but was just too loud. It was very deep and really screamed when I opened it up. I went back to the stock muffler but the power loss was so noticeable I was not satisfied.

I decided to cut open the stock muffler and see what I could do to open free up some flow without making a straight though shot and very loud. I cut both end caps off and ended up making the outlet on the rear like a normal exhaust. I gutted the the rear baffle out AND drilled five 3/8" holes in the remaining two baffles. The outlet is the same size pipe as the head pipe now. I actually got the bent section from an old harley head pipe. I trimmed it to shape and welded it in the rear end cap. Worked pretty well. I ground down all my welds on the can so you cant even tell it was ever apart.

In the end it was not nearly as loud as the HMF but it did bring back that power I felt with it. It gained enough power with this and my other mods that I had to put in 2g heavier clutch weights to keep it off the rev limiter. Any of you planning on modding your exhaust I think it works and sounds great. It gave it lots of power and sounds better but not nearly as loud as a straight through core like the Big gun, HMF, or Hot seat.

Heres a pic and vid. I think the vid makes it sound louder than what it is. Mods are 3.5 degree timing key, K&N filter with outerwears, opened up the factory snorkel, heavier clutch weights, and exhaust mod


http://youtu.be/EHbUmzoMDI4

[gmvk30]

Do you have any pics while it was cut apart? I'd like to do something like that to my SP500.

[Thomasj]

I didnt take any pics, I basically cut both ends off with a cut off wheel (be sure to mark the inlet side so your springs and pipe match up when you weld it back together), I cut everything out of the rear part of the muffler including the bottom outlet. When done you will only have the first baffle plate with the fan shaped passages and then the rear baffle with single hole in the middle. Nothing else. I then drilled the holes evenly around both of those plates. I drilled them so they do not line up so nothing is straight through. So there is two baffle plates in the first half of the muffler and the second half is basically and empty can with the packing around the outside. Be sure to leave the outer ring of any baffle you cut out. This will help hold the packing in place.

[cwlongshot]

Great post!!

I have been pondering this for some time!!

CW

[elmerkit]

Did you retune after installing your modified muffler?

[Thomasj]

No, the 800s are so rich from the factory its ridiculous. A good flowing exhaust wakes them up so much. It did more for this 800 than any other ATV Ive put exhaust on and Ive had so many I cant even remember them all without taking some time to think lol. If you just do a filter and exhaust on an 800 you do not need a fuel controller.

[vortecz71wv]

Ok so I just removed my stocker on my 2011 and I can see the fan shaped baffle. Would drilling the holes around this help any without doing any other mods?

[puppychow]

Thomas j -- first a compliment on the welds they look great . i to did this mod along with a K&N and although my welds don't even come close to being as clean as yours it really woke up the 800 .. thanks for the post and instruction i am loving the power gain i achieved with this inexpensive mod .

[Z-Rider]

Would this work on the Sportsman 500 HO? Anybody tried it yet? The welds on your mod are excellent, even better than some factory welds.

[super820]

How did you fill the old tail pipe hole?