Forgive me if it is bit crude, but I gotta ask...

[mr. happy]

So the big issue is that the stock jetting, air filter, and exhaust kinda neuter the bike a bit.

I can feel places in the powerband that feel right, and places in the powerband I know are way lean.  The deceleration when you roll off the throttle just screams that the engine is starved for air.

My previous bike I messed with was a lot smaller, more hinky, and generally less of a 'real' vehicle. (honda ct70)  As a result, instead of buying a new exhaust, I drilled holes in a pattern in the back of  the pipe to free up a bit more airflow.  Dropped a cheapo pod air filter on it, and voila had a HUGE increase in power with rejetting.  I ordered a variety pack of jets and dialed it in.

Has anyone tried the same method with the stock exhaust?  From what I read, the rejet, lunchbox, and stock exhaust isn't worth it to some.   I could easily see myself dropping 30 bucks on a lunchbox and 30 more on some jets, but throwing down 300$ for exhaust on a toy I paid 750 for is a bit harsh.  Yet every time I ride it, I can tell, hear, and feel the GS that could be there yearning to come out and play.  I wanna rejet, because of what I know my other bike went from to where it was at, and I can feel the gs there, but it's as I said before, a bit neutered at this point I feel.   

Has anyone here gotten redneck enough to go for a lunchbox, rejet and drilled out stock exhaust setup? 

For what it's worth, the way I did it with the other bike was rejetted way rich, then drilled out the exhaust till she was perfect.  I also backed out the needle 2 notches when I rejetted the ct70.  The result was perfect. 

Anyone tried the same here?  Bueller?  bueller?

So I guess my questions are twofold:  is stock exhaust, rejet and lunchbox really not worth it?
Has anyone drilled out their exhaust rather then just dropping coin on something new? 

[skudman]

So I guess my questions are twofold:  is stock exhaust, rejet and lunchbox really not worth it?
Has anyone drilled out their exhaust rather then just dropping coin on something new?

It seems to me by allotting more fuel, and more air, you get more exhaust so not replacing the can seems foolish.

And I'm sure someone has, lots of creative and knowledgeable folks on here. But it seems that the baffling inside the can would have to be removed to increase flow, and in doing so would likely remove the whole end cap. Then again I have never seen the inside of a GS can before...and I'm no mechanic

As far as spending coin on an exhaust it increases flow, in a hopefully scientific way involving formulas of size volume and pressure and is presumably lighter.

It sounds pretty mean too, in a street legal kinda way, for a 500.....487...

[Big Rich]

I'm sure there's some people around here that have done it. I recall seeing someones avatar was a soup can with holes drilled thru it..........

Personally, I would just go for the lunchbox filter and appropriate jetting, and forgo the exhaust (or maybe get a take off muffler from a larger sport bike). The jetting difference between a stock exhaust and a slip on usually isn't that much different.

[bigfatcat]

I rejetted up one step, drilled the stock exhaust  (not much, only a couple 1/8 in. holes)- very good results, compliments on how good the bike sounds.

Good power from 4300 to about 7 k rpm ... no flat spots.


  Oh yeah, and unifilter for stock airbox, and advanced ignition ~ 5 degrees.  Good enuff,  not wanting to make a boy racer out of the ujm gs.

[jestercinti]

I have a stock exhaust, and a lunchbox.  I'm at 20/65/142.5 3 turns 1 washer with Iridium plugs.  I have a more liner power curve and also have a more "throaty" intake noise.  Makes working on the carbs easier.  I have no issues being lean/rich/etc.  Warms up much faster too.

Drilling the exhaust and modifying the stock can is tricky.  There are catalysts (per se) and baffles that are not removable.  Can it be done?  Yep.  Has it been done?  Yep.  I think what you will find is that most people do the job poorly, resulting in a bike that not only performs worse, but sounds like sh!t.

I'm sure someone has done it right, but why waste a perfect exhaust can?  Buy a separate one to test.  If it fails, you can always go back to stock.

EDIT:  I have found that by modifying the exhaust too much, you end up smelling like unburnt hydrocarbons at your destination.  If that's your thing, then go for it.  I ride to my job rain or shine.  It's 12 miles from my house to my office in a skyscraper downtown.  I have a professional consulting job, so I have to look and smell presentable every day.

[Phil B]

So the big issue is that the stock jetting, air filter, and exhaust kinda neuter the bike a bit.

I can feel places in the powerband that feel right, and places in the powerband I know are way lean.  The deceleration when you roll off the throttle just screams that the engine is starved for air.

Call me a newb, but isnt engine braking something that people WANT?  it's rather important when you're going around a corner too fast and you dont want to put on more front brake? :-}

[mr. happy]

Thanks for the replies...

I'm not sure if everyone realizes I'm only talking about drilling holes in the very end cap.  I assure you without going deeper into any of the actual innards you will increase airflow by doing so.  I'm not thinking of drilling extra holes on the top or sides or something. 

Everyone also talks about getting great sound... I actually love the quiet stock pipe.  I know more air is gonna kill that a bit, but I don't mind a little stealth at 3 am at all.

And @ Phil, yeah, but there's a happy medium.  It's not like freeing up airflow through the engine will make engine braking stop, it will just be with less force.  If you are caught going through a corner too fast and engine brake,  the smoother force of the gear catching in the opened up engine may be the difference between sliding out and not too.

(but if you can engine brake and save it, that also means that there was traction there for using the rear brake and making it around upright too)

[iclrag]

It's completely up to you, and i've seen a few GS's with drilled exhausts, but i went with the expensive ass exhaust pipe, a K&N air filter (which BTW is about $50 not $30 american dollars anyways, not sure if you are in america) and rejetting soon