Improved KLX330S Exhaust
#1
03-02-2010, 09:26 PM
Improved KLX330S Exhaust
I knew I could lose some weight with an aftermarket exhaust, but the few I heard were irritatingly loud. Also, the stock hardware is tough - very reliable. So I thought the KLX300 would be a lower cost and good compromise. Now the stock exhaust worked fine on my 250, but I assumed I’d need more flow when I fit the 330 cylinder. I went straight to the 300 pipe when I did the cyclinder swap.
I found a dirty used KLX300 exhaust off eBay I fixed up. BTW the header pipe of the KLX300 header pipe is exactly the same in length and volume as the 250 header pipe. It differs only at muffler pipe attachment end, being larger to fit the larger 300 muffler pipe. The volume difference comes in after the header pipe, not before it. My KLX300 pipe came missing the baffle. I tried it, as was, and found it irritatingly loud. Loud also came insufficient backpressure which screwed up low-to-mid performance, despite jetting changes.
I've come to hate loud pipes, not only because they give excuse to the wackos to rob us of our freedom to ride, the loud bark pissed me off too. Rather, I prefer intake noise, which does not travel far or loosen fillings. I tried a plate baffle, but the bike still ran inconsistently down low and was raspy. I got pissed and threw the stock pipe back on, and, suprise! It worked really well! Quiet with lots of yummy intake roar. I got mad at myself for assuming the stock pipe would not work and spending money to make something worse. The 300 exhaust got stored away.
A year later I got an idea. Why not make a baffle somewhat like the stock muffler but larger? Maybe I’d have what I liked about the stock pipe but with more mid-to-top performance? This required some tube of the right diameter. I found it from a bent KL250 Super Sherpa stock handlebar. Some washers and TIG welding and I had myself a baffle!
The handlebar inner diameter is larger than a stock KLR650 pipe’s exit, and way bigger than the stock 250S pipe, so plenty of capacity. For better support, I ran the tube all the way into a well inside the pipe, shutting off the end. I then drilled 8 holes .190” diameter. All of the gasses pass through these holes, so I could control flow by hole diameter. The hole size was a guess, but worked well and I have not changed it.
The result is very near quiet as stock with the same low-to-mid performance and better mod-to-top performance. The bend in the tube also directs exhaust away from the rear fender. Here’s what the result looks like overall:
Been very happy with this.
I found a dirty used KLX300 exhaust off eBay I fixed up. BTW the header pipe of the KLX300 header pipe is exactly the same in length and volume as the 250 header pipe. It differs only at muffler pipe attachment end, being larger to fit the larger 300 muffler pipe. The volume difference comes in after the header pipe, not before it. My KLX300 pipe came missing the baffle. I tried it, as was, and found it irritatingly loud. Loud also came insufficient backpressure which screwed up low-to-mid performance, despite jetting changes.
I've come to hate loud pipes, not only because they give excuse to the wackos to rob us of our freedom to ride, the loud bark pissed me off too. Rather, I prefer intake noise, which does not travel far or loosen fillings. I tried a plate baffle, but the bike still ran inconsistently down low and was raspy. I got pissed and threw the stock pipe back on, and, suprise! It worked really well! Quiet with lots of yummy intake roar. I got mad at myself for assuming the stock pipe would not work and spending money to make something worse. The 300 exhaust got stored away.
A year later I got an idea. Why not make a baffle somewhat like the stock muffler but larger? Maybe I’d have what I liked about the stock pipe but with more mid-to-top performance? This required some tube of the right diameter. I found it from a bent KL250 Super Sherpa stock handlebar. Some washers and TIG welding and I had myself a baffle!
The handlebar inner diameter is larger than a stock KLR650 pipe’s exit, and way bigger than the stock 250S pipe, so plenty of capacity. For better support, I ran the tube all the way into a well inside the pipe, shutting off the end. I then drilled 8 holes .190” diameter. All of the gasses pass through these holes, so I could control flow by hole diameter. The hole size was a guess, but worked well and I have not changed it.
The result is very near quiet as stock with the same low-to-mid performance and better mod-to-top performance. The bend in the tube also directs exhaust away from the rear fender. Here’s what the result looks like overall:
Been very happy with this.
Last edited by Einfahrt; 03-02-2010 at 09:32 PM.
#4
03-03-2010, 03:44 AM
Nice work, Einfahrt. Novel approach. I'd think more holes might be in order as well, see what you think of this math...
The factory 250S baffle has one hole in it, with a diameter of 0.59 inches. The area of the exhaust (hold onto your hat!) is a whopping quarter of a square inch! No wonder we hear the bikes making the pffffft noise. So the stock exhaust restriction is 0.27 square inches.
You now have eight .190" holes. That has a total area of even less, at 0.23 square inches. Furthermore, if we want to get into boundary layer effects, the effective area is less.
So, just guessing here, I'd think another 8 holes wouldn't be a bad idea. As you've noted, you could do it two at a time to evaluate how much noisier the bike gets. I'm with you, I really don't want to make my 250 much louder at all, so I'm very intrigued by your solution.
Keep us posted!
The factory 250S baffle has one hole in it, with a diameter of 0.59 inches. The area of the exhaust (hold onto your hat!) is a whopping quarter of a square inch! No wonder we hear the bikes making the pffffft noise. So the stock exhaust restriction is 0.27 square inches.
You now have eight .190" holes. That has a total area of even less, at 0.23 square inches. Furthermore, if we want to get into boundary layer effects, the effective area is less.
So, just guessing here, I'd think another 8 holes wouldn't be a bad idea. As you've noted, you could do it two at a time to evaluate how much noisier the bike gets. I'm with you, I really don't want to make my 250 much louder at all, so I'm very intrigued by your solution.
Keep us posted!
#6
03-03-2010, 07:21 PM
Nice work, Einfahrt. Novel approach. I'd think more holes might be in order as well, see what you think of this math...
The factory 250S baffle has one hole in it, with a diameter of 0.59 inches. The area of the exhaust (hold onto your hat!) is a whopping quarter of a square inch! No wonder we hear the bikes making the pffffft noise. So the stock exhaust restriction is 0.27 square inches.
You now have eight .190" holes. That has a total area of even less, at 0.23 square inches. Furthermore, if we want to get into boundary layer effects, the effective area is less.
So, just guessing here, I'd think another 8 holes wouldn't be a bad idea. As you've noted, you could do it two at a time to evaluate how much noisier the bike gets. I'm with you, I really don't want to make my 250 much louder at all, so I'm very intrigued by your solution.
Keep us posted!
The factory 250S baffle has one hole in it, with a diameter of 0.59 inches. The area of the exhaust (hold onto your hat!) is a whopping quarter of a square inch! No wonder we hear the bikes making the pffffft noise. So the stock exhaust restriction is 0.27 square inches.
You now have eight .190" holes. That has a total area of even less, at 0.23 square inches. Furthermore, if we want to get into boundary layer effects, the effective area is less.
So, just guessing here, I'd think another 8 holes wouldn't be a bad idea. As you've noted, you could do it two at a time to evaluate how much noisier the bike gets. I'm with you, I really don't want to make my 250 much louder at all, so I'm very intrigued by your solution.
Keep us posted!
Good points.
Somewhere in any intake/exhaust system is the "smallest effective open area" (EOA), and that's typically the "weak link".
Yards and yards of tubing with 45 - 90 degree bends thrown in and flowing 30W oil (or even water) instead of air then other factors to consider.
With our little Kawi's not so complicated. Stock or after-market air filters are the MOST restrictive "component" but unfortunately kind a' necessary. So onto other stuff ...
34mm flat slide pumper (no butterfly valve in the way). EOA = 1.407 in2
Intake/Exhaust Valve(s). EOA = Heck if I know and not easy/cheap to change anyway ... next!
Header Pipe Inner Diameter. EOA = around 33mm (I think?) = 1.326 in2
Muffler Exit. EOA = you do the math & drillin'! .......... If you could get 1.33 - 1.41 in2 at an acceptable noise level ... " you be da' man".
Caution .. don't read further if ego preservation desired.
1 of 4 strokes is an exhaust stroke. 1 minute @ 10,500 rpm = exhaust flowing 2,625 strokes/min.
250cc engine displacement + 2,625 exhaust strokes/min = yawn inducing 23 cubic ft/min of exhaust flow.
Makes the mini-size shop vac in your garage seem like a nitro-methane fire breathing monster. Yeah, but I still LUV my little Kawi
someone double check my math, as I'm now really depressed about the whole matter.
Last edited by LongmontKLXr; 03-04-2010 at 02:19 AM.
#8
03-04-2010, 02:30 AM
I knew I could lose some weight with an aftermarket exhaust, but the few I heard were irritatingly loud. Also, the stock hardware is tough - very reliable. So I thought the KLX300 would be a lower cost and good compromise. Now the stock exhaust worked fine on my 250, but I assumed I’d need more flow when I fit the 330 cylinder. I went straight to the 300 pipe when I did the cyclinder swap.
I found a dirty used KLX300 exhaust off eBay I fixed up. BTW the header pipe of the KLX300 header pipe is exactly the same in length and volume as the 250 header pipe. It differs only at muffler pipe attachment end, being larger to fit the larger 300 muffler pipe. The volume difference comes in after the header pipe, not before it. My KLX300 pipe came missing the baffle. I tried it, as was, and found it irritatingly loud. Loud also came insufficient backpressure which screwed up low-to-mid performance, despite jetting changes.
I've come to hate loud pipes, not only because they give excuse to the wackos to rob us of our freedom to ride, the loud bark pissed me off too. Rather, I prefer intake noise, which does not travel far or loosen fillings. I tried a plate baffle, but the bike still ran inconsistently down low and was raspy. I got pissed and threw the stock pipe back on, and, suprise! It worked really well! Quiet with lots of yummy intake roar. I got mad at myself for assuming the stock pipe would not work and spending money to make something worse. The 300 exhaust got stored away.
A year later I got an idea. Why not make a baffle somewhat like the stock muffler but larger? Maybe I’d have what I liked about the stock pipe but with more mid-to-top performance? This required some tube of the right diameter. I found it from a bent KL250 Super Sherpa stock handlebar. Some washers and TIG welding and I had myself a baffle!
The handlebar inner diameter is larger than a stock KLR650 pipe’s exit, and way bigger than the stock 250S pipe, so plenty of capacity. For better support, I ran the tube all the way into a well inside the pipe, shutting off the end. I then drilled 8 holes .190” diameter. All of the gasses pass through these holes, so I could control flow by hole diameter. The hole size was a guess, but worked well and I have not changed it.
The result is very near quiet as stock with the same low-to-mid performance and better mod-to-top performance. The bend in the tube also directs exhaust away from the rear fender. Here’s what the result looks like overall:
Been very happy with this.
I found a dirty used KLX300 exhaust off eBay I fixed up. BTW the header pipe of the KLX300 header pipe is exactly the same in length and volume as the 250 header pipe. It differs only at muffler pipe attachment end, being larger to fit the larger 300 muffler pipe. The volume difference comes in after the header pipe, not before it. My KLX300 pipe came missing the baffle. I tried it, as was, and found it irritatingly loud. Loud also came insufficient backpressure which screwed up low-to-mid performance, despite jetting changes.
I've come to hate loud pipes, not only because they give excuse to the wackos to rob us of our freedom to ride, the loud bark pissed me off too. Rather, I prefer intake noise, which does not travel far or loosen fillings. I tried a plate baffle, but the bike still ran inconsistently down low and was raspy. I got pissed and threw the stock pipe back on, and, suprise! It worked really well! Quiet with lots of yummy intake roar. I got mad at myself for assuming the stock pipe would not work and spending money to make something worse. The 300 exhaust got stored away.
A year later I got an idea. Why not make a baffle somewhat like the stock muffler but larger? Maybe I’d have what I liked about the stock pipe but with more mid-to-top performance? This required some tube of the right diameter. I found it from a bent KL250 Super Sherpa stock handlebar. Some washers and TIG welding and I had myself a baffle!
The handlebar inner diameter is larger than a stock KLR650 pipe’s exit, and way bigger than the stock 250S pipe, so plenty of capacity. For better support, I ran the tube all the way into a well inside the pipe, shutting off the end. I then drilled 8 holes .190” diameter. All of the gasses pass through these holes, so I could control flow by hole diameter. The hole size was a guess, but worked well and I have not changed it.
The result is very near quiet as stock with the same low-to-mid performance and better mod-to-top performance. The bend in the tube also directs exhaust away from the rear fender. Here’s what the result looks like overall:
Been very happy with this.
MacGyver ... "main asset is his practical application of scientific knowledge and inventive use of common items".
If I could find "jumping up-down and clapping animated GIF's" I'd insert a row of em' here.
#9
03-04-2010, 10:20 AM
Oh no, don't induce physics into this tuning stuff
Good points.
Somewhere in any intake/exhaust system is the "smallest effective open area" (EOA), and that's typically the "weak link".
Yards and yards of tubing with 45 - 90 degree bends thrown in and flowing 30W oil (or even water) instead of air then other factors to consider.
With our little Kawi's not so complicated. Stock or after-market air filters are the MOST restrictive "component" but unfortunately kind a' necessary. So onto other stuff ...
34mm flat slide pumper (no butterfly valve in the way). EOA = 1.407 in2
Intake/Exhaust Valve(s). EOA = Heck if I know and not easy/cheap to change anyway ... next!
Header Pipe Inner Diameter. EOA = around 33mm (I think?) = 1.326 in2
Muffler Exit. EOA = you do the math & drillin'! .......... If you could get 1.33 - 1.41 in2 at an acceptable noise level ... " you be da' man".
Caution .. don't read further if ego preservation desired.
1 of 4 strokes is an exhaust stroke. 1 minute @ 10,500 rpm = exhaust flowing 2,625 strokes/min.
250cc engine displacement + 2,625 exhaust strokes/min = yawn inducing 23 cubic ft/min of exhaust flow.
Makes the mini-size shop vac in your garage seem like a nitro-methane fire breathing monster. Yeah, but I still LUV my little Kawi
someone double check my math, as I'm now really depressed about the whole matter.
Good points.
Somewhere in any intake/exhaust system is the "smallest effective open area" (EOA), and that's typically the "weak link".
Yards and yards of tubing with 45 - 90 degree bends thrown in and flowing 30W oil (or even water) instead of air then other factors to consider.
With our little Kawi's not so complicated. Stock or after-market air filters are the MOST restrictive "component" but unfortunately kind a' necessary. So onto other stuff ...
34mm flat slide pumper (no butterfly valve in the way). EOA = 1.407 in2
Intake/Exhaust Valve(s). EOA = Heck if I know and not easy/cheap to change anyway ... next!
Header Pipe Inner Diameter. EOA = around 33mm (I think?) = 1.326 in2
Muffler Exit. EOA = you do the math & drillin'! .......... If you could get 1.33 - 1.41 in2 at an acceptable noise level ... " you be da' man".
Caution .. don't read further if ego preservation desired.
1 of 4 strokes is an exhaust stroke. 1 minute @ 10,500 rpm = exhaust flowing 2,625 strokes/min.
250cc engine displacement + 2,625 exhaust strokes/min = yawn inducing 23 cubic ft/min of exhaust flow.
Makes the mini-size shop vac in your garage seem like a nitro-methane fire breathing monster. Yeah, but I still LUV my little Kawi
someone double check my math, as I'm now really depressed about the whole matter.
the exhaust out out would be larger than intake due to the expansion of the fuel+air?
ie if 250cc of air + fuel go in to the combustion chamber a larger amount of gases would leave due to them expanding through heat.
you get use to the loudness of the bike.
i think you will get what you are looking for if you remove the muffler completely
#10
03-04-2010, 12:32 PM
Jey I'm jazzed! There's intelligent life here! Good repies that is. And I see my buddy the great mind of Watt-Man is here too.
I tend to run against some cultural trends, like loud = better (that selfishness is giving our enemies ammo), or geared lower = !acceleration! (um, not that simple). I generally gear bikes up not down, and try to get a lot out of humbler bikes with little coin.
Yes, my 8X Diameter .190" sums only to an area of .226 inches square, but I suspect that is enough. When I did my 4-springs clutch mod test to see if the clutch would slip, I was doing max acceleration runs upslop and against the wind on the highway. The stock carb butterfly went max open and the power started going soft at 95 mph (no clutch slip at all, BTW). I suspected limiting oput not due to flow limitation, a slightly lean 128 main jet. Didn't make any adjustment going from 250cc to 330cc yet.
Gonna pop in a 132-135 and see if that allows WFO under same conditions to be 100 mph on this bike with my standard final drive gearing being 1 tooth up on the front (with good throttle-clutch technique that works fine for the tight off road stuff too).
Maybe what I'll do first is slip the baffle out and scare the cows along the road and see if the flow issue makes a difference. Then rejet, then open up more hole if needed.
I tend to run against some cultural trends, like loud = better (that selfishness is giving our enemies ammo), or geared lower = !acceleration! (um, not that simple). I generally gear bikes up not down, and try to get a lot out of humbler bikes with little coin.
Yes, my 8X Diameter .190" sums only to an area of .226 inches square, but I suspect that is enough. When I did my 4-springs clutch mod test to see if the clutch would slip, I was doing max acceleration runs upslop and against the wind on the highway. The stock carb butterfly went max open and the power started going soft at 95 mph (no clutch slip at all, BTW). I suspected limiting oput not due to flow limitation, a slightly lean 128 main jet. Didn't make any adjustment going from 250cc to 330cc yet.
Gonna pop in a 132-135 and see if that allows WFO under same conditions to be 100 mph on this bike with my standard final drive gearing being 1 tooth up on the front (with good throttle-clutch technique that works fine for the tight off road stuff too).
Maybe what I'll do first is slip the baffle out and scare the cows along the road and see if the flow issue makes a difference. Then rejet, then open up more hole if needed.
Last edited by Einfahrt; 03-04-2010 at 12:39 PM.