Dual Tail Pipe Mod...

Technocyclist

Technocyclist

Motorized Bicycle Senior Technologist
I have been doing some research on exhausts, and based on the dimensions of the exhaust port, the maximum tail pipe inside diameter should be 16mm. My stock exhaust only has 8mm, so I drilled a 10mm hole beside the existing tailpipe and inserted a 3/4in. male brass coupling. The coupling is held together by some exhaust glue I bought from a Hardware store. It now performs very well, lots of torque, but does not really increase RPM. Four stroking is minimized if not eliminated. I'm using a shift kit with a Shimano Alfine, and continues to climb hills even in 8th gear.

I did rebore the male coupling with an 8mm drill bit to get the right size. The noise has not increased subtantially and is still within tolerable levels. I can't seem to remove the end cap of the muffler, so I guess this is the best that I could do. More gases do flow from the 2nd tail pipe. The stock muffler does not have a cat. This is the one that has single bolt in the middle of the end cap.

Still saving up for a tuned pipe, so this is probably the next best thing...

Has anybody else tried this?
 

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This is a great idea. I may have to try this myself. Having just the one tailpipe must just be way too restrictive on the exhaust flow with that little outlet.
 
I did this a while back,

I went even further, I put a 10mm bit through the end caps center mounting hole then the internal outlet where the screw used to go.

I hold the cap on with a hose clap now.

Its louder and faster, 3mph more on my dyno/test hill,
 
I had a similar idea with good results!
 

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To Russell.

Where did you find the Schwinn speedo? did it come with the chopper? I had one but at this point is now DEAD.

Any help would be great!

And also, do you have your headlight connected to the white wire?
 
Heres one I did a year or so back. I attach a choke cable to the baffle unit inside the stock exhaust. When I wasnt in town I could slide the baffle out and when I came back I pull it in and be back to normal levels. I needed to change the pull slide to a lever because sometimes if there was a fast increase in rpm it would try to push out the baffle. Just something to think about.
Terry
 

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Russell said:
How much preformance difference is there?
Click to expand...

I'd say there's an increase in torque. Since I have a shifter kit, I compare the gear range hill climbing ability. Before, on the same hill, I used 4th or 5th gear, with this mod, I can now climb in 6th or 7th gear on the same hill, ofcourse, the speed also increases since a higher gear is used. :D
 
I just recently tried drilling a hole and placed a Cupling in it.
But now, i cannot get my motor to idle. Ive played with the idle screw and throttle and it doesnt even make a difference.
Did you have this problem? Or did anyone? And how did you solve it?
 
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I really doubt that it is the exhaust.
That mod has more effect at higher RPM. Check your throttle tube and see if it is fully closing. These kits are known for throttle grip and cable problems. I will be watching to see how this is resolved.

GL Russ
kzbesner said:
I just recently tried drilling a hole and placed a Cupling in it.
But now, i cannot get my motor to idle. Ive played with the idle screw and throttle and it doesnt even make a difference.
Did you have this problem? Or did anyone? And how did you solve it?
Click to expand...
 
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Wierdest thing. I checked the idle screw again and found that it had broken off inside the carburator.
And ya, my throttle is a bit odd as well :P
found a new screw that looks exactly identical in my dads shop, i slapped it on and now she idles but its not entirely steady.
 
i find my pipe has a heck load of torque eversince i put a 49cc pocket bike expansion chamber on though the only way mine fitted was by passing the exaust system over the engine and under the seat

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Thought I would share this dual pipe bike...
 

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If that is yours continue reading: laff
That is probably the weirdest and coolest bike I've ever seen. I'm super jealous. Do you have any videos on it and is there an old build thread I can read? Thanks.
 
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