stock exhaust

[markmax]

Has any one drilled the end caps with larger holes on the stock exhaust. If so, what do I need to do to do this. I'm about to give up on getting my cobra exhaust sealed. I'm tired of riddig down the road and hearing the leaks. But I hear you can get more sound from the stock if you modify it?:confused2:

 

[Waylander]

Ran into a guy here the other day that had done something like that.

He drilled the rivits out of the back plate then drilled a few extra holes into the bit behind that then re-riveted the back plate on with spacers behind it to give it a bit of a gap. Sounded nice at idle but didn't get to hear it at speed.

 

[mikemax04]

Has any one drilled the end caps with larger holes on the stock exhaust. If so, what do I need to do to do this. I'm about to give up on getting my cobra exhaust sealed. I'm tired of riddig down the road and hearing the leaks. But I hear you can get more sound from the stock if you modify it?:confused2:

I've done it to mine. Like Waylander said, drill out the 5 rivets holding the back plate on, using a #3 drill bit. Then on the same bolt-circle drill 3/8" or 1/2" holes in between the rivet holes, depending on how loud you want it. You can replace the plates any time you want to by tapping the rivet holes 1/4-28 and using standard fasteners, with or without spacing the plates. Ask questions if unsure of anything.

 

[shawn kloker]

You can also make a bigger hole in the middle of the plate.I used an electrical knockout punch to make it larger.

 

[markmax]

Does doing this require a jetting change. I think I might be moving in a year or so. Just wanted to hold off on re-jetting untill I get to a lower altitude if I can.

 

[shawn kloker]

I think that you will be fine.I am running stock mains in mine right now with stage 7 and hmf exhaust.
Don't be afraid to pull the plugs once in awhile and see how it is burning.

 

[markmax]

I've done it to mine. Like Waylander said, drill out the 5 rivets holding the back plate on, using a #3 drill bit. Then on the same bolt-circle drill 3/8" or 1/2" holes in between the rivet holes, depending on how loud you want it. You can replace the plates any time you want to by tapping the rivet holes 1/4-28 and using standard fasteners, with or without spacing the plates. Ask questions if unsure of anything.

So did you drill the holes on the cover or is there a plate behind the covers where you drilled the larger holes.
Thanks for the help.
Mark

 

[Buster Hymen]

I've done it to mine. Like Waylander said, drill out the 5 rivets holding the back plate on, using a #3 drill bit. Then on the same bolt-circle drill 3/8" or 1/2" holes in between the rivet holes, depending on how loud you want it. You can replace the plates any time you want to by tapping the rivet holes 1/4-28 and using standard fasteners, with or without spacing the plates. Ask questions if unsure of anything.

Mike, take some pictures, looks like a good addition to the FAQ.

 

[Rusty McNeil]

If you want really effin loud try this;

I did it after running mine with the end cap just drilled for awhile and wanting something a little more noticable.

What I ended up with is a LOT more noticeable.

Take a sawzall or sabersaw and cut the whole back cap out the fullest circumference you can without getting into the sidewalls of the big can (it's got a really thick and probably heavy wall on it maybe 3/4" of an inch.

You can use a die grinder to clean it up and give it a nice even circumference afterwards.

After that pry, force, wiggle the whole damn thing till the whole assembly comes out. You will have a hole you can stick you fist down into.

Then take a really long drill bit or drift pin/punch and perforate the living heck out of what is down in the can about a foot deep until there is not very much left of it.

Be sure and use a vaccum cleaner hose down the pipe as you go so you don't leave anything to get sucked up towards the heads due to camshaft overlap...

Essentially what you end up with is an empty can with no muffler except the dampening material on the sidewalls of the can.

It's very loud, not raspy, roars at throttle and has a really wicked idle with the V-boost wired open.

To the rest of the biker world it will sound very distinct from any inline 4 or vtwin out there.

Don Smith told me it was a butcher job but of course I expected that. It doesn't look like a butcher job at all; just a big exit hole.

Very noticeable and gets a lot of complements except for those who get wierd about loud exhuasts.

It leaned me out a little but with shimmed needles and two coils off out of the slide springs the A/f ratio is just about right.....

Rusty

Good luck getting it inspected unless you go some place where they pass the loud ass Harley exhausts on inspection.

Rusty McNeil

 

[mikemax04]

So did you drill the holes on the cover or is there a plate behind the covers where you drilled the larger holes.
Thanks for the help.
Mark

Leave the cover intact and only drill out the rivets. With rivets drilled out, remove caps and you will see a semi flat portion about an inch wide where the bigger holes can be drilled ON THE SAME BOLT CIRCLE as the rivets. Use a center punch and indent where you will drill the new holes. Nothing critical but center punch half way between the rivet holes and in the center of flat area. Reason for the #3 or 7/32"drill bit is so you can tap the same holes 1/4-28, which is better than 1/4-20 because it's thin walled and finer thread holds better. This procedure allows you to re-install the plates anytime you want to and the bigger holes will be covered up and you're back to the stock setup. Some drill the rivets out with a 1/4" bit and this allows you to replace end caps with 1/4" rivets. Reason for tapping the holes is so you can space out the end caps by placing a 5/16" nut between the caps and the muffler.......or whatever distance you choose. I started with just the 1/2" holes but found it to be a bit tinnish sounding. Tried a couple of 11oz (?) empty coffee cans with the bottom cut out too, and gave it a 1" snip down one side with tin snips to force it into the muffler opening for trial. To me it sounded a lot better already. I progressed to 5" SS resonators. Sounds gooood and looks different and I like being an individual. It's easy to do, with no risk of messing up the mufflers if you want them looking and sounding stock again.

Tools needed: Drill, #3 or 7/32" and 1/2" drill bits, center punch, hammer and 1/4-28 tap

 

[shawn kloker]

I like the whole gutting the cans idea!Could we see a pis of them?

My cans were scraped up when I got it so I went to supertrapps shortly after buying it.I ran it drilled for a couple weeks.Trapps for a couple years then hmf's.

 

[Waylander]

If you want really effin loud try this;

I did it after running mine with the end cap just drilled for awhile and wanting something a little more noticable.

What I ended up with is a LOT more noticeable.

Take a sawzall or sabersaw and cut the whole back cap out the fullest circumference you can without getting into the sidewalls of the big can (it's got a really thick and probably heavy wall on it maybe 3/4" of an inch.

You can use a die grinder to clean it up and give it a nice even circumference afterwards.

After that pry, force, wiggle the whole damn thing till the whole assembly comes out. You will have a hole you can stick you fist down into.

Then take a really long drill bit or drift pin/punch and perforate the living heck out of what is down in the can about a foot deep until there is not very much left of it.

Be sure and use a vaccum cleaner hose down the pipe as you go so you don't leave anything to get sucked up towards the heads due to camshaft overlap...

Essentially what you end up with is an empty can with no muffler except the dampening material on the sidewalls of the can.

It's very loud, not raspy, roars at throttle and has a really wicked idle with the V-boost wired open.

To the rest of the biker world it will sound very distinct from any inline 4 or vtwin out there.

Don Smith told me it was a butcher job but of course I expected that. It doesn't look like a butcher job at all; just a big exit hole.

Very noticeable and gets a lot of complements except for those who get wierd about loud exhuasts.

It leaned me out a little but with shimmed needles and two coils off out of the slide springs the A/f ratio is just about right.....

Rusty

Good luck getting it inspected unless you go some place where they pass the loud ass Harley exhausts on inspection.

Rusty McNeil

Was thinking about something similar to that today. Unfortunately down here in the Nanny state, that would quickly catch the attention of the cops. And any attention from the cop here usually results in some extortionate fine. Not indicating at a round-a-bout costs $500 if caught where as running a red light only gets $150. Go figure. Stupid Hideous Helen Clark and her **** ass blanket laws.

 

[Rusty McNeil]

I like the whole gutting the cans idea!Could we see a pis of them?

My cans were scraped up when I got it so I went to supertrapps shortly after buying it.I ran it drilled for a couple weeks.Trapps for a couple years then hmf's.

I will try as soon as I can. I'm in the middle of a turnaround at work right now so working 13/13 with one day of every two weeks.....I know someone wanted pics of the airhorn setup too so eventually I'll get to it......
Fortunately I can get on this forum at work......

 

[98blackmax]

i have a bone stock 98 max and i unscrewed the little plates on the back of the pipes, do i need to rejet?:confused2: bikes got 35k on it dont feel like melting **** now lol

 

[Rusty McNeil]

I don't think so; it takes a fairly drastic change to need rejetting.

actually, and this is just my opinion, going from a stock exhaust to the absolutely most free flowing set up you could find neccesitates a jet change for performance reasons.
I don't think you could go lean enough to actually damage anything......

My opinion only...

 

[mikemax04]

Has any one drilled the end caps with larger holes on the stock exhaust. If so, what do I need to do to do this. I'm about to give up on getting my cobra exhaust sealed. I'm tired of riddig down the road and hearing the leaks. But I hear you can get more sound from the stock if you modify it?:confused2:

Mark, here is what the back of the muffler looks like (sort of) when the 1/2" holes are drilled. This picture is looking down a one foot long X 5" SS diameter tube I call a resonator. Gives a much deeper sound. I also plugged the rivet holes to get away from that Pffft sound. Hope this helps you on the location of the holes.