brute force 750 with exhaust baffle removed

ojcool · May 10th, 2007, 12:32 AM

Quote:

At first I thought about just drilling holes all the way through it but after I got the silencer out and shown my flash light into the turbine to see what was back there I decided on pulling out the turbine and opening it up some and then drill the holes where some of the exhaust would have a straight shot out. You can see in the pics that I drilled one hole then stopped The turbine actually directs the exhaust towards the center of the end cap so it doesn't just hit the back of canister and bounce around.
My biggest gripe about the HMF was it didn't hold up to the mud.......Of course they have been trying to tell us that.[/b][/b]

Acutally I did both. I opened up the turbine like you did and drilled holes anywhere I could.

When I first took on this mission I cut about one inch in from the end of the pipe. I took out the last chamber baffle and drilled holes in the chamber that was exposed (one right after the turbine). Welded it all back together and rode. It barely made the exhaust any louder so I figured, what the hell I'll take out another baffle, thats when the turbine got exposed and I went to town. I also got a really long bit and went through the turbine to the chamber behind it and put as many holes in as I could. Even with all that done it's MUCH quieter than any aftermarket exhaust I have heard. It's more smooth and deep. People ask me all the time what kind of exhaust it is.

Something to note about this modification (and I'm sure STOGI will attest to this) the last chamber before the exhaust exit of the muffler is by far the most restrictive part of the exhaust due to the angled tailpipe internally being so close to the last baffle. I would think you could enjoy most of the power of an exhaust with almost No additional volume by removing just the last baffle and nothing else.

Great Mod if you have a welder.

Tj Craig · May 10th, 2007, 04:18 PM

MEN,
I installed the HMF UTILITY SERIES muffler, loud ? yep ! I Installed a Quiet core AND IT TONED IT DOWN enough for me, why would someone spend that kinda of money for a GREAT exhaust system and go back and Jerry rig the stocky ?? WOW !
Tj

STOGI · May 10th, 2007, 08:23 PM

Quote:

MEN,
I installed the HMF UTILITY SERIES muffler, loud ? yep ! I Installed a Quiet core AND IT TONED IT DOWN enough for me, why would someone spend that kinda of money for a GREAT exhaust system and go back and Jerry rig the stocky ?? WOW !
Tj[/b][/b]

After a while the HMF gets unbearable. I tried the quiet core but it made it sound like crap, even raspier. Ain't nothing wrong with take your skills and experimenting . I promise this exhaust will last allot longer that that HMF I had. There's a reason HMF has made a new series of exhaust with baffles and no packing

ojcool · May 13th, 2007, 12:33 AM

Quote:

MEN,
I installed the HMF UTILITY SERIES muffler, loud ? yep ! I Installed a Quiet core AND IT TONED IT DOWN enough for me, why would someone spend that kinda of money for a GREAT exhaust system and go back and Jerry rig the stocky ?? WOW !
Tj[/b][/b]

The Modified stock exhaust sounds alot better in my opinion than any of the aftermarkets I have heard. Plus as I posted, It must flow better as well due to the bike needing to go two steps up in main jet above what HMF recommends. So to answer you question.... Sounds better, flows better. Just becasuse you paid alot for something does not mean it's good. But if your happy with your exhaust thats great. Everyone has a different preference.

STOGI · May 13th, 2007, 06:49 PM

I think one reason it's flowing better is because the exhaust is dumping into a canister that's twice as large as most aftermarkets . Once we remove some of the restriction in it the pulse is freer to move around and escape.

Slowsome · May 23rd, 2007, 10:47 PM

Ok, I did mine almost the same as the one in the pics. The only difference is with the end cap. I didn't cut mine flush like you did. I just removed the packing in it. But I drilled holes in the one baffle behind the finned baffle and opened the fins up like you. I have one complaint about it. When you let off at a slow speed it whistles. There are no holes in the welds either. Its sealed up fine. I don't know why it does this. It sounds good under acceleration but on the decel I was disappointed. I am thinking about cutting the end off and modding the first baffle now. I guess I should have drilled holes or something. My brother modded his and the only difference in the way we did ours was he driled holes in the finned baffle and I opened the baffles up more. His sounds great on accel and decel. They do have a different sound as well when you rev it.

What do you guys think my whistling problem is?

catzuki · May 24th, 2007, 12:19 AM

So what about jetting. Do u need to rejet for this mod. I also plan on putting in a K&N and a prefilter. So anyhelp would be awsome. I just need a starting point to jet for. I ride any where from 3000-6000FT. Thanks for any help.O ya and i also would like to add an intake snorkel .

STOGI · May 26th, 2007, 09:09 PM

Quote:

Ok, I did mine almost the same as the one in the pics. The only difference is with the end cap. I didn't cut mine flush like you did. I just removed the packing in it. But I drilled holes in the one baffle behind the finned baffle and opened the fins up like you. I have one complaint about it. When you let off at a slow speed it whistles. There are no holes in the welds either. Its sealed up fine. I don't know why it does this. It sounds good under acceleration but on the decel I was disappointed. I am thinking about cutting the end off and modding the first baffle now. I guess I should have drilled holes or something. My brother modded his and the only difference in the way we did ours was he driled holes in the finned baffle and I opened the baffles up more. His sounds great on accel and decel. They do have a different sound as well when you rev it.

What do you guys think my whistling problem is?[/b][/b]

I think this may be a combination of the turbine swirling the pulse and the size of the outlet in the end cap......I notice a slight "hiss" on decel when I had the snorkel on it......now it's a mellow bbbbbbbbaaaaaaaaaaaaaaaa...lol

Slowsome · May 26th, 2007, 10:37 PM

Quote:

I think this may be a combination of the turbine swirling the pulse and the size of the outlet in the end cap......I notice a slight "hiss" on decel when I had the snorkel on it......now it's a mellow bbbbbbbbaaaaaaaaaaaaaaaa...lol[/b][/b]

I think I may try and open it up like you did. I can't handle the whistle...lol