Expansion Chamber

fairracing31 said:
http://motorbicycling.com/f28/post-more-pictures-how-post-pics-916.html

http://motorbicycling.com/f15/how-post-pictures-61.html

A little more detail here on posting pics
http://motorbicycling.com/f28/how-post-pictures-3446.html#post32930

I hope this helps
If you need any more help Michael....just ask :)
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Just using: Image: http://bike195.jpg

Will not work. You need to scroll down when making a post and click on manage attachments and updload it. OR get on a photo hosting site (or use your own site)
 
Well this is very maddening!!! I managed to get the picture of my wifes bike on my profile if anyone wants to see it.My bike is the same type of set up . Their both incrediably FAST 40 mph +++ Power band is in low range middle range & high range.This expansion chamber is desigened for my tanaka 47r motor. Note my regular muffler added on to my silencer at end of pipe. It makes this set up really quiet. With no power loss. Allso note the blue rubber tubeing ,made to with stand very high temps. Theirs no leaks on this setup at all
 
Just installed expansion chamber on my bike using a 49cc setup as a donor, this thing is scary quick accelerating with my 44t. Now need to install my custom made reed valve, walbro hda63 and smaller sprocket to see what this thing can really do. I recommend this mod and the port mod to anyone who wants a smoother running engine, and added performance for cheap.
 
Good to see another convert :) Most people who experience a before and after with an expansion chamber on their motor tend to have this reaction and a few days later when they change the gear ratio to a lower numerical ratio they are plesantly suprised to feel a longer smoother surge of power that isn't the jump out from under you startling blast.

Where did you get your reed valve conversion ? I'm sure that will mellow out the piston port induction too.
 
I dont mean to hijack anyones thread but i plan to do a thread on this when im done performing it. I ordered a 49cc reed valve for a scooter off ebay and plan to make my own manifold. I looked into the pipelyne product and believe in supporting the small business but couldnt cough up the money they want for one. But their product will look nicer than what im thinkin of puttin together... but if it works and i saved some money than im happy ;)
 
Jak - I am looking at the picture you posted. I think you need to get more of the shape of a set of cones, it looks too much like a larger section of pipe in the middle of a pipe. Also you will need to lose the original muffler, you have retained all the restriction. The muffler you see in the pic's the others have posted is for a two stroke and makes up the (Stinger) end of the pipe. Google "two stroke expansion chambers" I think this will help with your design. Have fun, Dave
jak stoll said:
so here is the second attempt
it will look better when its painted up
have a great weekend
JAK
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Has anyone taken the proper measurements for use in the program that was posted earlier?

I was thinking about trying to make one kind of like Jak is trying. Was hoping to try out using some reducers, etc to make the transitions...or anybody got measurements of their pipes?
 
Yes, I pulled my engine off the bike, pulled it down removing the exhaust manifold (it has one) in order to get the measurements of the exhaust port which is rectangular. From there I pulled the carb and plug off and used a mini maglite to see the transfer port opening on the cylinder and rotate the crank thru from opening to close of the ports. Likewise the exhaust the same way.....

I got the specs for my Tanaka Free Spirit recently and found the rpm for max torque and hp and maximum RPM. Just don't know first hand the exhaust temperature at operating speed.

You can see what I posted here. The Java software I used is less than what I would like to design with and then go to the bench to make. It was fun playing with it on paper though.

If anyone wants to see it it's here.

http://motorbicycling.com/f13/another-home-made-pipe-3477-3.html
 
hey there dave :-)
I did pretty well did gut the muffler (cut off the tube on the lower piece
the first one was larger & I will probably make a better one or buy a better one & adapt it
take care
JAK
 
3rd try

this is the one I did tonight
I think 3 times is a charm
this muffler may be loud though
take care
JAK
 

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Jak that is looking pretty good. I have to give it to you for persistence, and welding skills. The long center section, the portion that just carries the wave is designed for a slow revving engine, I know you knew that. The first cone amplifies the sound wave the last cone drives it back and shoves the fuel that escaped the port back, acting like a supercharger. The way you tune a pipe is to calculate the speed of sound, and then time it to return to the port at the speed you need it. That looks like a 5hp Briggs muffler, I don't know if that will work it has a block 1/2 way through, all the stingers we used to put on were straight and the length has an affect on the tune of the pipe also. Good work keep it up. Have fun, Dave

PS: If I were guessing at the size of the stinger you need, I would say 1/2 id. and 6" long to start with. You can use a two stroke muffler that emulates those dimensions.
 
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hey thanks for the kind words
I have no shortage of mandrel bends here & make the cones by cutting triangles out of pieces of exhaust pipe with my chop saw
I did use more of a stinger on the back this time the tube diameter inside is 5/8 & is pinched almost shut in the middle with holes drilled on either side of the restriction the outer diameter is 2.25 this is a bit better then the briggs one because probably 30% of the exhaust gasses can still pass through the pinch & I can tune it by pounding a large screwdriver through the pinch :-)
Ill keep messing with it :-)
take care
JAK
 
Jak - You may have seen this, but this is the coolest thing I ever saw. I wish they had computers and animation in my day, I am kinda the guy that needed the visual on everything. LOL. Have fun, Dave
Two Stroke motor - an overview

PS: I don't know why but we used to trim the stinger at different lengths and change the power. If we got it too short we would weld the piece back on.
 
I spent more time on the pipe today
I lenthened the first cone & shortened the second cone, shortened the center section also made the outlet smaller than the inlet
I put on a stock muffler
the result is that the engine really woke up particularly higher in the revs
I think I nailed it this time
with the last one it got terrible fuel milage & was slugish, I think that the center section was too long & that the cones werent different enough
it pulls rite where I want it too not too high but at a good RPM for speed & probably some climbing
Ill get a pic up when I can
Im also going to look for a nicer muffler
take care
JAK
 
Jak I don't know if you are up to it, but if you are willing to do the ports and take advantage of the scavenging that pipe is made to do, you will get a real head turner. I can't remember who it was that used my porting and the pipe, he also has the shift kit, said he can pop wheelies. Look over in engine mods for porting. Have fun, Dave
 
Egor said:
Jak I don't know if you are up to it, but if you are willing to do the ports and take advantage of the scavenging that pipe is made to do, you will get a real head turner. I can't remember who it was that used my porting and the pipe, he also has the shift kit, said he can pop wheelies. Look over in engine mods for porting. Have fun, Dave
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yeah I did that :-)
lowered & widened the intake side & verry slightly raised the exhaust port & widened it
everything is gasket matched
as it turns out though the case from the engine that I just put together got screwed up when the main bearing failed
so the engine is noisy & you can take the magneto rotor & move it up & down :-(
I have another assembled bottom end which I took apart. cleaned out & inspected that Ill switch out today
the cylinder is niceley broken in allready
take care
JAK
I also raise the compression
it helps allot thruout the RPM range
 
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OK did you lower the intake also? about 1/4 not more, I can never remember who asked these questions. LOL. The intake is a big one. Have fun, Dave
 
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