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exhaust port (Read 2580 times)
klx650sm2002
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Re: exhaust port
Reply #15 - 06/04/10 at 10:32:39
 
Looks like after to me. It's upsidedown too.
Clive W Smiley
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ralfyguy
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Re: exhaust port
Reply #16 - 06/04/10 at 10:42:50
 
So where is the piece to grind off?
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klx650sm2002
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Re: exhaust port
Reply #17 - 06/04/10 at 11:17:39
 
The round bit just inside the port, mostly gone in that pic.
Clive W Smiley
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Truckinduc
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Re: exhaust port
Reply #18 - 06/07/10 at 19:09:06
 
here these pics I took might help. This is just to remove the ring.  If you are careful you can do it with the motor all together.

Before



After



Process

1. remove exhaust and battery ground.

2. turn over motor by hand until you hit compression stroke.

3. Make sure exhaust valves are fully closed and seated.

4.  spray a Little shaving cream in to the valve area.

5. stuff paper towels into each port.

6. Port head with whatever tool you prefer, like a die grinder or dremel. I port matched mine to my exhaust. Thats the shiny ring in the first picture.

7. vacuum all shavings out. If any got past the paper towels the shaving cream will catch them. Vacuum it out too.

8. Re install exhaust and battery, your done.

Really not that hard if you take your time and be careful.
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LANCER
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Re: exhaust port
Reply #19 - 06/08/10 at 04:37:08
 
klx650sm2002 wrote on 06/04/10 at 10:07:09:
Lancer, are the valve springs above that horizontal bit in the top of the port, how much is it safe to take off there ?
Clive W Smiley


Yes, the springs are on the other side of that "wall"

Not sure exactly about how much was removed...did not measure; just went by "feel"; I wanted to be sure to have enough material to maintain structural integrity.
I did not remove much, just enough to round off what was a sharp pointed peak before.

The most important part of the process was to smooth the area just below the valves and to round out the "inside corners" within the ports.  These were hard to get to and nearly impossible to photograph.
I used emery cloth torn into narrow strips and run through the ports so I had an end  to grab hold of on each end of the port; then did a back-n-forth motion (like flossing teeth) and repeated it for the medium/med-fine/fine grits that I had available.
The ehaust follows the shortest path in the ports and that requires that the inside corners be as smooth as possible to reduce any hindrence of the air flow
That was my goal at least...we shall see if I did this correctly or not.

I was following the technique of a Harley dude with some reputation for building world record engines for the salt flats.  I figured he must know something about it and so went with it.  Of course, it would have been helpful to have the good tools and some time to develope proper technique under his direct guidance....but you go with what you've got.
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Bubba
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Re: exhaust port
Reply #20 - 06/08/10 at 07:21:31
 
Truckinduc, what did you notice as far as performance improvement doing just the exhasut port?
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'06 lt Blue, Dyna Power pipe, air screw 2 1/4 turns, 52.5 pilot w/ bleed holes, 150 Main, 2/3 spacer, Pirelli MT66 tires, Raptor petcock, 412-4006 Progressive shocks
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bill67
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Re: exhaust port
Reply #21 - 06/08/10 at 08:05:39
 
anytime you make ports bigger you lose on the low end power and gain on the high end.
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william h krumpen
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ralfyguy
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Re: exhaust port
Reply #22 - 06/08/10 at 10:52:03
 
So it's like putting a free flow muffler on. How would it affect a stock carb jetting, spacer 2/3 and the baffle removed from the stock muffler like mine. It runs very good like that with smooth throttle transitions and pretty good power up to about 90mph. Problem is, I was thinking about doing the exhaust port job, but don't have the guts, because I don't know how the effects will be. What if it totally ruins the way it runs now. There's no way back, other than a new head. Or I have to do all the other stuff with airbox and rejet and it never will be right. Will the theoretical gain be worth the try? Or would the difference not justify the risk? I am not that much of a hard core engine tuner. I like the idea of a better cam and stuff, but I don't think I'd be up to actually doing it. The spacer and exhaust mod, as well as doing the mixture screw already made it a 1,000 times better running than when I first got it. If I knew that the exhaust port mod would just give a little more ooomph without having negative effects, I'd go for it in a heartbeat. I just don't know how it's gonna be.
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bill67
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Re: exhaust port
Reply #23 - 06/08/10 at 11:05:56
 
Go up one jet richer on the high speed will give you more power,And you just have to drop the fuel bowl to do that.
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william h krumpen
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Re: exhaust port
Reply #24 - 06/08/10 at 12:04:42
 
with the port a little larger, the exhaust moves a little more freely out of the engine; just like a HD muffler flows a little more air than the stock muffler; both result in a little more power.
More air (exhaust) out allows more air (fuel/air mix) in which makes more power.

same with the performance camshaft; the valves are open a little more and stay open a little longer, resulting in more exhaust out and more fuel/air mix in = more power.

all fun stuff......  Wink
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ralfyguy
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Re: exhaust port
Reply #25 - 06/08/10 at 16:16:34
 
How about the low end? Right now it pulls from 40mph to 70mph in about 9-10 seconds in 5th gear on level ground.
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Re: exhaust port
Reply #26 - 06/08/10 at 18:12:25
 
You will lose that low in power,And you'll have more on top if thats what you want.
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william h krumpen
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ralfyguy
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Re: exhaust port
Reply #27 - 06/08/10 at 19:37:42
 
I guess I'll just leave it the way it is. I like the torque for mostly in town riding. It's got plenty of Hwy power already. Lots of people complain that it runs outta breath at around 70. I don't have that feeling. If I wanna go past a car on the Hwy, and I crack it open at around 70, I get past it fairly quick. Once I get back in the right lane, I look at the speedo and darn I'm at 90 already, and it wasn't downhill.

A while back a Dude on a 500 Ninja and I had it going on a red light. We took off and the Dude had his Ninja screaming, and after about almost 1/2 mile I had to throw the anchor at 95, not to miss my off ramp into town and the Ninja had about just 15 yards advantage. Sure the Ninja was faster, but didn't impress me at all. I was very surprised, because I expected to get smoked badly. To me that little Savage is a beast.  Smiley
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earlytimz
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Re: exhaust port
Reply #28 - 06/08/10 at 20:58:56
 
bill67 wrote on 06/08/10 at 18:12:25:
You will lose that low in power,And you'll have more on top if thats what you want.


Sorry Bill... Bad info there
You are not gonna "lose" that low end torque. Here's how I know...

I did a midnight special port job on my head. I opened the exhaust side to match the factory pipe, also took off the ledge and smoothed everything out. Nothing really aggressive, just gave her a good massaging. I then hit the seams on the intake side & took off the protruding stud. This side aint too bad.

Now... I have a 150-90 rear tire which is quite a bit taller than factory. I also have a 4 speed trans (higher geared). To top it all, I think I'm still a little lean on my needle. So with all these things adding up you'd think I lost all my bottom end...

The result???
Well I can pull out of a curve at 30mph in high gear without a problem. I honestly wish I had a 5th gear because I have no doubt it would pull it. I'm in Ky, we have plenty of hills. I can hit any hill around here in 4th gear and pull all the way up. Even the one on my way home that requires me to drop down to 40- 45 because of a curve at the bottom of it. No problems whatsoever, just open her up and she grunts down and pulls like a diesel truck.

Yes, you need back pressure to optimize torque. Even with the porting, there is still a D shaped squeeze in that port. After that, you've got a tight bend in a small I.D. pipe, then most likely some kind of baffle in your muffler. There's no shortage of back pressure.

Trust me, opening up your head will not hurt your performance. That exhaust port is the most restrictive design I've ever seen on anything... EVER. That ledge is ridiculous! It's like a friggin parachute in there. Open it up & take advantage of a better scavenging effect. That's where the exhaust pulse creates a vacuum that pulls out the next pulse. It's the reason a 2 into 1 pipe makes more power on a v-twin. It also applies to big singles (& V-8's & 4-bangers, etc...) & is mostly affected by the pipe I.D., which isn't changing. You're just making it easier for the engine to push out the exhaust gases.

It's just like Lancer explained... More in = More out, More out = More in

It's an easy job. You don't even have to pull the head (although you prolly should) There's plenty of meat in there, you'd have to get really aggressive to do any damage. Check out the pics that have been posted, get a good bur bit & go to town. Take your time & be precise. You won't regret it.
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earlytimz
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Re: exhaust port
Reply #29 - 06/08/10 at 21:33:05
 
Sorry, once I get going on something it's hard to shut my mind off...

This picture is hard to read but explains the scavenging effect, or exhaust driven induction effect, I was talking about. I know it says race motor (a motor is electric, btw), but that's because race engines are built to optimize power & torque, where factory engines are built for emissions & economy & they could care less about scavenging.

They describe it as a 5th stroke. It's the vacuum created by the exhaust pulse pulling out the next exhaust pulse, in turn pulling in the next intake pulse during the valve over-lap.

Confused yet? LoL... It's legit, it works... Open that head up and let it breathe!!!!!

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