Anyone ever heard of this being done or had it done?

heck them little japan cars have the fart can exhausts, im sure you can make your 4 wheeler sound like one of them!

Well I have a '95 Polaris Sportsman 500 that I paid $400 for. It runs but the whole exhaust system was rotted out. It was either pay big bucks for a whole new OEM/aftermarket system or have a buddy put a whole new system in but use a new small car muffler instead of the "correct" type muffler for $60 total. I chose to only spend the $60 on my $400 wheeler. It doesn't look that bad and it's not really all that loud. It runs a lot better because it has back pressure now, something it hasn't had since I bought it. There ya go. It can be done.
BTW, the wheeler in my profile pic is an old Yamaha Moto-4 350 that runs awesome.

Good thinkin Curly...you wanna sell it to me? $460 cash money, tomorrow even...

Actually the Moto-4 is my woman's wheeler...I need the Polaris till deer season is over.

just jokin with ya man...it sure would be nice to run across one for that cheap that just needs a little tlc

Yeh I got lucky. It was a taxidermist buddy of mine's. It had been setting in his yard, exposed to the elements for over a year. I bought a new battery for it, put new gas in it and it fired right up.

This is it after I got it home, cleaned it up and added the saddle bags:

you got REALLY lucky, I almost bought that same quad last year but it was a 400, the guy was selling it for $2200, which was a pretty decent price!

Craigslist my friend! That's how we found my woman's Moto-4. We don't regret buying it at all! Search motorcycles and recreational vehicles for 4-wheelers and ATVs. She paid $800 for the Moto-4:

I was going to say backpressure would be the only issue I could think of but it sounds like it helped more than hurt. If you can get a picture of the mod I would like to see it. I wonder if it is quieter than the stock muffler?

I'll try to get a picture and down load it. It isn't quieter than a stock muffler but it is a lot quieter than it was. It kinda looks like one of those muffler silencer add-ons you can buy that mount on back of a wheeler.

My hunting buddy put a tractor muffler on his ATV; it quietened the exhaust noise significantly, and performance hasn't suffered at all. His is a 500cc Suzuki.