Today with nothing better to do (the wife and kids went out for a bit) .. I did a little experiment based on the modification suggested by RedFuelDlux.  I strapped a coke can on to the end of my exhaust can which effectively extended the "outer" pipe about 2 inches.

It sure sounded "different"!?  It sounded a little bit like the exhaust popping sound of a small displacement 2-stroke or maybe a popcorn popper.  It sure didn't sound like a Harley anyway,LOL.  :lol:  The wierd noise might be because of the very thin aluminum of the popcan.  It didn't really seem to change the exhaust note above 5000rpm.

I might have noticed too a slight reduction in power but it wasn't much.  Also, once you get past about 50mph you can't hear it for the windnoise anyway.  

I think I will try the RedFuelDlux exhaust mod but just cut a little bit at a time.

Any body else performed any experiments?

Rob

Haven't performed any of these experiments but if you get to where you feel a power increase, let me know and I will try to duplicate the setup and run it at the track.  

By strapping on a coke can you are actually changing quite a few very important things and you have to look at the intake side to see them.  I may get some details wrong and I don't prefess to be an expert in the application but I know the theory and in general, this is how it goes.

It takes a given amount of time for the exhaust pulse to travel the length of "tube" from the exhaust valve to the tip of the exhaust pipe.  You can think of it as a bubble traveling down the pipe with vaccuum in between the next/previous bubble - like little beads.  At the moment the bubble pops out the tip of the exhaust pipe, you want a similar but unspent bubble to be present at the back of the intake valve.  This way, when the exhaust bubble pops out the end, this little tiny vaccuum actually pulls the chain of bubbles (exhaust pulses) that are in the exhaust pipe.  This pulling continues up the exhaust pipe, through the combustion chamber, all the way to that intake bubble sitting at the back of the intake valve.  You want it to be timed properly so that you take advantage of that exhaust bubble popping out the end - you get it to actually PULL the intake bubble into the combustion chamber where it is made to do work for you.  

The same "length thingy" for lack of a better technical term happens on the intake side.  You have to size the intake tract length and the exhaust length to match each other so that all the bubbles in the tube push/pull and help each other along.

Strapping on a coke can may seem like an inocuous thing but it is actually changing BIG things.

That's a cool description of how air flows through the motor.  My initial reason for trying the experiment was to see if there was any performance changes from changing exhaust tip configuration.  It seemed like I lost a bit of top-end power.

BTW, I have a stock set-up except for V&H ignition advancer.  I am thinking of putting on the K&N pod type air filters and rejetting carbs.  

Thanks!

Cool! Keep us informed on your progress.



RFD

Yes. I DID it over the weekend...
I cut the inner pipe about more than an inch, almost to the end where it touches the muffler. I couldn't cut it in an angle that RFD recommended because it was hard to do, so I just cut it straight.  Here are the results:

1. Got a quite pleasant base sound - not quite strong and loud as I like it to be, but I am happy with it cause I understand this is a GS500, not a Monster 900 Duc.
2. No change in performance whatsoever. Any where above 5K RPM, the engine sound superceded the exhaust sound.
3. When park, I like to give a few rev of the throttle to hear the pleasing GRRRRRR (base sound) as the result of this mod.

Next to do:
What if I added the 6 holes drilled into the muffler. Does anyone try this before ?

Glad to hear you like the growl! I never tried the "6 hole around the pipe mod", but I did use a 12" drill extension (Bought at any Hardware store for around 4 bucks) and drilled a single 3/8" hole inside the pipe. It made it a little louder when revved. If that's not enough, you can always try the 6 hole mod later.

RFD

Quote from: SoloRider
Next to do:
What if I added the 6 holes drilled into the muffler. Does anyone try this before ?

Joris did a write up. Just do a search for his page.