new expansion chamber design

The pipe came off a 49cc pocket bike so I added a five inch extension. I also made the second tip in the center of the pipe. Made a plug for the tips out off a wine cork works great.
 
Nice design GXSR, have you thought about adding a forward bleed somewhere on the divergent cone? You're already getting great low torque from the center bleed and the top speed from the end bleed maybe a forward bleed will boost the mid-range torque resulting in the best of all 3 worlds. Just a thought.......
 
Yes there's a big difference in the power band with the end bleed it's mostly at the top.
With the center bleed the power band covers all of the range.
I'm guessing that the motor is able to breath better with two tips and still getting the pipes supercharging effect.
 
I think I'm going to keep it this way for now don't want to mess it up. You know if I mess
With it to much I might mess it up. I'm just going to wait for the DAX RT carb should be here in the next few days
 
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Mod list
*38t sprocket
*port match intake,exhaust and polish
*main jet swap 76mm a bit rich
*needle clip at top notch
*stock carb port and polish
*carb slide mod I have found that by taking a bit off entry face. It makes idle leaner adding to it makes it richer this really affects the throttle response it's the angle of the air going in.
*NGK iridium plug BPR6HIX
*upgrade spark plug wire from subs speaker wire 4 Gage copper core.
*throttle cable adjustment to be on the sweet spot
By the way 66cc slant head I have been able to recuperate all lost torque. From the sprocket change and seeing speed numbers of 36-38mph.
*
 
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GSX, would you be willing to share some dimensions on the exhaust you have there. i'm looking at building my own and i'm not too sure where to start with the chamber.

thanks
 
DuctTapedGoat said:
Banana pipes only deliver at top end, you don't need to compare.
Click to expand...

interesting observation. I'm comparing a pocketbike 49cc expansion chamber with an sbp chamber currently. the engine isnt broken in yet so it may be kinda moot, but the longer, smaller pocket chamber seems to keep 'er popping more. "on the pipe" as one may say.
the SBP has a shorter headpipe, and it runs much richer with this pipe on it. . so much so that I believe jetting is mandatory with this larger diameter chamber, and perhaps will yield a larger HP output when jetted.
seems that the pocket chamber is a great "non'jet" mod. I am at sea level and on 3rd clip. here are photos pof the pipes (on different bikes) but i'm testing on the black bike

any thoughts or similar experience?
 

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Since no two engines perform quite the same, I think the only way to get a fair comparison of two different pipes would be with the same engine on the same bike. That's how I compared my 2 pipes. One has more low end, the other has much more top end.
TiM
 
timboellner said:
Since no two engines perform quite the same, I think the only way to get a fair comparison of two different pipes would be with the same engine on the same bike. That's how I compared my 2 pipes. One has more low end, the other has much more top end.
TiM
Click to expand...

Notice I wrote," pipes are
On different bikes, but I'm testing on the black one. "

The pictures are reference for the pipes pictographically. I am using the engine on the black bike to test both pipes.
 
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