stock expanchan chamber Q

[buzzy613]

I was lookin at my 85 250r's expanchan chamber and was wondering has anyone attempted to gut it out? if there is anything in side of it i would like to gut mine, my buddy told me about guys doing this to there banshees and i was wondering is it possible?

[dcreel]

I've never cut one open neccesarily but I'm pretty sure there isn't anything to gut. I think some oem pipes were double walled but don't think the 250r expansion chambers were.

[just ben]

pretty sure it's expansion, nothing in there to gut out nor is there on a banshee. It would be the silencers they gut out. I wouldn't recommend it, I would just find an aftermarket silencer.

[beets442]

X2 Chamber is empty. Now if there is oil caked in it, I've use a small map torch to heat the pipe lightly to burn the carbon out.

[Chazz of Blades]

my buddy told me


There's those words again!

And I'm pretty sure there's nothing to strip out, they aren't like the muffler on a four stroke.

[WilliamJ]

If there is anything in it it won't work as an expansion chamber! It is designed to change the velocity of the exhaust gases at specific points in the cycle and rev range and its shape is critical to the way the engine performs.

Whatever you change on a 2 stroke exhaust will definitely have an effect on the power. Different shape chambers and pipes give different engine characteristics. You need to be able to reverse whatever you do in case it doesn't work.

[RIDE-RED 250r]

There are no baffles in a 2-stroke expansion chamber (header pipe). The expansion chamber pipe uses sound waves that reflect back from the far tapered end of the pipe before the silencer to aid in the intake/exhaust cycle. Different expansion chamber profiles will cause different power curves on a typical 2-stroke. Its all about the timing and strength of the return of that sound wave.

In other words, its a fairly precise science that takes alot of know-how to customize. So, dont mess with it! LOL! :)

[El Camexican]

There are no baffles in a 2-stroke expansion chamber (header pipe). The expansion chamber pipe uses sound waves that reflect back from the far tapered end of the pipe before the silencer to aid in the intake/exhaust cycle. Different expansion chamber profiles will cause different power curves on a typical 2-stroke. Its all about the timing and strength of the return of that sound wave.

In other words, its a fairly precise science that takes alot of know-how to customize. So, dont mess with it! LOL! :)

Agree, but wouldn't the correct term be "pressure" waves? Maybe they are one and the same, or could both be in play inside a pipe? Damn this gr.6 edumacation of mine!

[RIDE-RED 250r]

Well, sound is actually a form of pressure. Im thinking one in the same in this case..... :beer

[WilliamJ]

You are both right because it is referred to generically as pressure wave tuning, and the waves travel at the speed of sound. Of course the sos varies according to the temperature, pressure and density of the air it is travelling through.

By all means mess with it but do some detailed research first and be prepared to fail. So don't cut up the pipe you are using, make another. There was an expansion pipe calculator on here (Java Pipe: Tuned Pipe Designer is how it shows on my bookmarks) but I couldn't get it to work on my Mac and my windows machine is no good at the moment. Anyone try it?
Bill

[RIDE-RED 250r]

You are both right because it is referred to generically as pressure wave tuning, and the waves travel at the speed of sound. Of course the sos varies according to the temperature, pressure and density of the air it is travelling through.

By all means mess with it but do some detailed research first and be prepared to fail. So don't cut up the pipe you are using, make another. There was an expansion pipe calculator on here (Java Pipe: Tuned Pipe Designer is how it shows on my bookmarks) but I couldn't get it to work on my Mac and my windows machine is no good at the moment. Anyone try it?
Bill

You hit the nail on the head.. Its kinda like porting. Yes, you can learn the science, but its gonna cost you a fair bit of time and cylinders to port, and try... trial and error. Not something your average shadetree mechanic like most of us can really pull off with any degree of success...

Before i get pounced on, note i said MOST of us!! LOL! Im sure with all the collective experience in this forum's membership roles there are some who have the tools, know-how and experience to do this, and have done with success...

[briano]

Cut open a stack banshee pipe, they do have a muffler type set up in the chambers. It's possible the older trikes do to

[El Camexican]

I've only seen two vehicals with "stuff" in the expansion chamber. One was a John Deere snowmobile which I tried to "fix" and ended up with no bottom end and no top end, but it had a mid range bang that would lift the skies at least 2' off the ground on hard pack (steel channels running across the track). My Dad ended up paying the dealer around $300 for a new pipe so he could drive the sled again and that got me banned from the shop for a few months. The other was a 500 Yamaha V4 that I never cut open, but I could feel the baffels with a wood stick. I'd be surprised if a race oriented machine like a 250R had such obstructions in it.

It would be something to see how a place like FMF determines how a pipe is to be made, but that said if any of you are old enough to remember all the different pipes available for the RD 350 back in the day and how when the magazines would test 5 or 6 of them, you'll recall that the stocker would usualy be ranked near the top in performance. That tells me it's not easy to build a better all round pipe than the one that came on your machine from the factory. I think most people just assume louder is faster without taking the time to test things.

[Chazz of Blades]

I think Honda has proven that louder is NOT faster in the car division.