Dax Expansion Chamber Exhaust?

mogollonmonster · Apr 27, 2016

Chrome banana shaped expansion chamber, it's bolt on ready for $40. Has anybody here used it? I've been told it will help lean the bike down, on top of other performance enhancing things... I've jetted down to quite a small size (.24 if I remember right) and the bike is still really rich. I've drilled my exhaust cap and opened up the ridiculously small flange, will the expansion chamber still lean it down, and will I still notice a power gain?

Chaz · Apr 27, 2016

I don't have direct experience with that pipe but double check that it does not have baffles in it, which would defeat the purpose. Some bananas have baffles and some do not but they look very similar. And as I understand things you are correct that you should get a power gain and lean out by adding an expansion chamber.

Tyler6357 · Apr 28, 2016

I agree with Chaz but I would point out 2 things, (1) the header is pretty short so your performance increase will be mostly top end and (2) it's going to be very loud

leo · Apr 28, 2016

i got one of the hollow ones.
no noticeable power gain, and it was quite a bit louder too. i went back to the stock exhaust for now, i plan to get an SBP exhaust later.

mogollonmonster · Apr 28, 2016

My bike is already obscenely loud, so I won't likely notice a volume change. As for powerband, will the lack of header kill my low end power? I could use some more poop up top, but not at the expense of the ability to get up there.

Is the Dax unit hollow?

I just don't want to shell out cash for a new dust collector. I no longer own a welder so fab work is out of the question, I'm just looking for a bit of bolt on power, and hopefully a leaner running motor.

Chaz · Apr 28, 2016

Here's a thread for you to read. Some good info.

http://motorbicycling.com/showthread.php?t=59935

Cylon · Apr 30, 2016

Chaz said:
I don't have direct experience with that pipe but double check that it does not have baffles in it, which would defeat the purpose. Some bananas have baffles and some do not but they look very similar. And as I understand things you are correct that you should get a power gain and lean out by adding an expansion chamber.

Why do you say a baffle hurts it? I had a banana pipe and switched to a pocket bike exhaust and only gained 2 mph. The baffle didn't affect it much just made it quieter. I understand the expansion chamber acts as a baffle alone but the engine doesn't really notice a baffle that much.

Cylon · Apr 30, 2016

mogollonmonster said:
Chrome banana shaped expansion chamber, it's bolt on ready for $40. Has anybody here used it? I've been told it will help lean the bike down, on top of other performance enhancing things... I've jetted down to quite a small size (.24 if I remember right) and the bike is still really rich. I've drilled my exhaust cap and opened up the ridiculously small flange, will the expansion chamber still lean it down, and will I still notice a power gain?

I ran a fred head and those generic muffled banana pipes with my wife during a 15 mile ride and I had a higher top speed. I was able to gain almost 1/4 a mile by staying WOT vs her stock motor. People may say its not optimal but it is better then the stock pipe. 2 stroke motors NEED an expansion chamber to run at their best. Save your money and get a pocket bike exhaust I'll provide a link to my latest test with a expansion chamber made from a pocket bike and a very simple way too hook it all up.

Good luck,
http://motorbicycling.com/showthread.php?t=61132

Also with a new pipe you should rejet your engine or you will lean it out and it will destroy itself before its really matured. I used a #75 jet at 118 elevation. Stock it was a #60.

Chaz · Apr 30, 2016

Cylon said:
Why do you say a baffle hurts it? I had a banana pipe and switched to a pocket bike exhaust and only gained 2 mph. The baffle didn't affect it much just made it quieter. I understand the expansion chamber acts as a baffle alone but the engine doesn't really notice a baffle that much.

Cylon,

One banana, two banana... I'm baffled. Anyway, a pipe that has baffles is not an expansion chamber. Anything that interferes with the pressure waves will diminish the effect. My explanation for your results is that the banana you had on was less restrictive than the stock exhaust and your new pocket chamber is small. The real advantage of an expansion chamber is to increase your torque, it won't really effect your top speed that much.

https://en.wikipedia.org/wiki/Expansion_chamber

happy riding

Cylon · Apr 30, 2016

What do you mean by my pocket bike exhaust is small? Did you even read my latest post?

Chaz · May 1, 2016

Yes, I read it. I was just giving my opinion about expansion chambers and my preference is for a bigger pipe. I don't doubt that you got some performance increase with the pocket pipe. Where in your rpm range is your pipe most noticeable? I would guess more low end torque?

mogollonmonster · May 1, 2016

Cylon did you read my post? My welder was stolen! I need bolt on! No choppy choppy, not zit zot, its all lickem stickem now. I understand the pocket bike expansion chamber is a better choice, it's just not viable as an option. I can't really modify anything, nearly all my tools were stolen in January, else the title of this post would be "Who has the best expansion chamber, and is willing to let me copy it?"

When I speak of jetting, it's an ulterior motive for the new pipe. I'm down to my smallest micro drill, something tiny like .024in, can't tell for certain because my micrometer was jacked too. The bike is still to rich, by a lot. I'm banking on the idea that the expansion chamber will lean me out enough that I have to jet back up.

Thanks for the links guys, learned enough to know it's a good idea, and that it should blow my Swiss cheesed stocker out of the water. Payday cometh...

Cylon · May 1, 2016

The pipe added more low and mid end power, but it really pulls good I got it running great. Check out the video section I have a video there showing the bike cruising.

Chaz · May 1, 2016

Good to hear it. I've got two pipes to go onto two bikes. One is off a yz80 (pretty large) and the other is off a small ktm like bike that I bought a few years back and has a really well made chamber about the size of yours or the crmachine voodoo pipe. I'll be looking for the same power band you have. I want the acceleration to get up to speed and climb hills somewhat. I'm getting over 30 mph with stock set up now and don't really need to go any faster but want to get there quicker and put on a smaller sprocket to cruise at a bit lower rpm.

And I want to make it a belly bleed to bring the sound level down. Check out the difference in this video. https://www.youtube.com/watch?v=qsQ_mRrqrTs

cheers

mogollonmonster · May 1, 2016

So guys, from all the homework you gave, I gather that I'll see a few more rpm (possibly) as a result of increased torque? I'm fine with that, the bike runs plenty fast enough, I'd just like to lean it down and cruise uphill a bit better. Sounds like the banana will do just that.

I'll look into other pipe/chamber options later on, but Dax will get my money for this first time around. Call it a proof of concept test.

Chaz · May 1, 2016

Monster, yep the dax banana should serve your purpose. Let us know how it goes when you get it installed.

mobike91 · May 13, 2016

Only complaint I had with the Bananas was that my pedal crank hit the pipe. Let us know what you think of it.

mogollonmonster · May 13, 2016

Yah about that... I've had to dent my stock pipe and grind down the end of my crank arm because they hit, might be an issue...

mogollonmonster · Jun 1, 2016

Ok so the banana got here today, but because I ship my parts to my boss, I didn't have time to work on anything.

Mating surfaces of the flange are horrid, but it looks ok otherwise. I now have the maintenance shop at Pine Meadows Country club at my disposal, so I'll fix the flange tomorrow. I don't think Duane saw it, or he wouldn't have sent it out, it's so bad. I'll put some photos in the albums tomorrow for those interested.

mogollonmonster · Jun 2, 2016

Well, I got the mating surface fixed up, and put it on the bike.

Noticeably more torque, still a little four stroking till it warms up. Much quieter than my Swiss cheese stocker. Much better crank clearance, good overall appearance, although shoddy up close due to ugly welding.

Time will soon tell if I invested or wasted my money lol.

Dax Expansion Chamber Exhaust?

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