Made an expansion chamber tonight!

the longer the header, the more limited in rpm the engine is.
you will just have to try it and see how it is. it may not be too bad.
but without a belly stinger it will be LOUD.
my advice is to cut the belly length in half, put a baffle on thats 50% longer (for a wider powerband), and insert the stinger till it starts at the end of the belly section.
 
It is extremely LOUD! Too loud... The belly section is 3" diameter, and roughly 4" long. If I'm understanding you correctly I need to make the belly about 2" long??? And do I need to make the cone on the back of the belly 50% longer?? I'm trying to make sure I understand what you think will work best for it.

I did test fire it, and besides being extremely loud, it definitely doesn't rev up like it used to... It's been raining like crazy here, so I haven't been able to test it out for torquiness. I'm hoping it'll pull hills better, since I only have a 32 tooth on it, but I don't want to lose my 35 mph either.
 
yes you understood me right.
the sad fact about expansion chambers is that they only enhance power within their powerband (typically a 2000 rpm range) and will stop any rpm increase beyond a bit more than the top of their powerband. And when the baffle angle is steep (like yours) it robs power before you rev up into the powerband.
For a single speed ride the baffle cone (the last one) should have a very slight angle for a wide powerband thast doesn't rob power below the powerband.
2 or 2.5 inches is the normal max belly diameter for these engines.
If you want to be precise in your design then just download my Excel file of Expansion Chamber Calculator (ECcalc) and make good use of it.
 
Ok thank you very much! I will test it the way it is, and if it needs changed I'll drop the diameter of the belly, and lessen the angle on the baffle cone. Thanks again.
 
Update. I installed the stinger, I used a lawnmower muffler, and added a belly stinger to it. I took some conduit and measured it so it would start at about the middle of the belly. Then welded that to the lawnmower muffler, then welded that mess to the expansion chamber. It is actually very reasonable with the sound level, it revs pretty decent, and HOLY $HIT did it give this thing some bottom end!!!! I can start off from a dead stop under engine power, without pedaling WITH A 32 TOOTH sprocket!! I love it! And I did it all myself, with the help of this forum! Thanks guys!
 

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Skyhawk, I think it's a great forum . But, you have to remember, that not everyone that visits a post can give GOOD advice. We are all here because we enjoy building and riding. Some are old pro's, and some because we are new and what to read as much as we can, as some day we may need the references. Immersed with what I have seen of your build, not everyone has the tools and where-with-all that you do. Keep posting.
 
I think it is great you are trying.I have built a few pipes, but to make one right you do indeed to do
the math.I remember in my kart racing days, a few guy making pipes that did work very well, but
just looking at them I would think no way.

As far as stingers, some thing I have not seen with these bike pipes.Our pipes used cans welded to
the rear & closed except for a hole cut in the side to let presser out.It reduced noise, & worked very
well.

I,m going to build a pipe in the next few weeks, after I finish my bike & break the engine in.I will
post a pic as to how I did it.

Fly
 
As far as stingers, some thing I have not seen with these bike pipes.Our pipes used cans welded to
the rear & closed except for a hole cut in the side to let presser out.It reduced noise, & worked very
well.



Fly

bit like how i cut the end of the stock muffler and use the can here?

yep. works a treat.:)
 

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