Poo-poo pipe

Discussion in 'Spare Parts, Tools & Product Developement' started by Gimmick, Oct 5, 2007.

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  1. Gimmick

    Gimmick Guest

    so i found a long "poo-poo" pipe, (the one on the grubee web site) for 29.99 on ebay and bought it. It arrived yesterday and I wanted to share my impressions with you all... if this post would be better in reviews please feel free to move it there.
    The welds are not the nicest beads ive ever seen, kind of globby and pooled, but they seem sturdy enough, the chrome plating is fair.
    The flange fits well. the bends on the pipe contour the engine and frame beautifully. Looks hella cool! Had to do some fooling around with the angle of the muffler to achieve peddle clearance due to the idler pulley mount, but worked it out.
    Started her up, and sounds good. Lots of pop-pop, and 2 stroke sounding.
    Immediatly felt a big increase in low end torque on my 70cc. Got to 24mph very quickly, but then seemed to flatten out considerably. I usually get to 28 mph with my 50 tooth at redline. I couldnt get past 25, but also wasnt making as many rpms.

  2. JemmaUK

    JemmaUK Guest


    It sounds like it might not be tuned correctly to the engine - emphasising bottom/mid range at a cost to high end power. In order for a pipe to work at all levels you need a three stage pipe...

    I have one other suggestion and it comes from (I think) an old maybach racing car.

    It had a straight 8 engine with brass fittings and a straight through exhaust... the fun part was there was a valve arrangement on the exhaust itself that allowed the driver to open up the exhaust thereby shortening it to about 3 feet long and giving a useful boost of power for overtaking...

    another thought is a bypass pipe passing the pipe to a muffler with a handlebar control to allow you to shut off the pipe when you want higher speed..

    Jemma xx
  3. forrest

    forrest Guest


    Not sure about the "poo poo" Pipe, but in most cases if you put on a "tuned" pipe on a two stroke engine most of the the time you have to "up jet" your carb ( You Need More Gas). I think with the happy time engines you can do this somewhat by adujusting the needle, I m not sure because I do not have a Kit yet! I would do a plug chop and see if you are running to lean now. Im sure somebody will chime in that has more experince than me with the happy time engine. Hope that helps some.

  4. Just curious BUT if this pipe gives more low and mid end power could one simply gear up a bit (i.e. use a smaller rear sprocket) to achieve a possible overall increase in speed (at the same time the engine RPM's for a given speed would be somewhat less because of the gearing and maybe this would result in an overall decrease in engine wear (less RPM) and possibly even greater economy (geared higher)?

    PS - I'll have to read up some more but by cutting the header length and rewelding you can alter the RPM of the powerband....I think a longer header is more for low/mid power and short header is for High RPM use...I'm glad you posted re this pipe because I have been curious about them...Thanks!
  5. retro_racer

    retro_racer Guest

    Andy,Dude I'm so proud of you.Man you've came a long way since you first started.You are exactly right.If you change the gearing you will get alot better top end.It still sounds like the pipe isn't an exact fit for the motor.Question is the pipe designed for a 70cc motor?Tuned pipes are usualy designed to give a small over all increase in power(through all 3 ranges).I've heard that they can also be designed to increase just the top end or the bottom end power ranges.depending on the size of the chamber.The problem is I'm not sure if them ment the diameter or the length.I would think either or would change the volume of the chamber.Good job Andy!!!!!
  6. retro_racer

    retro_racer Guest

    I found alittle more info for you guys.By changing the gearing you will also change the power bands.Your 50t sprocket will give you more torque(zippy take offs,and less top end).Were a medium say 40t will actualy even out the power bands,and say a 30t should kill alittle of the low end but give it back on the top end.Changing the gears dosn't actualy change the power bands.It affects were they come into play in the cycle.Hope that helps.
  7. JemmaUK

    JemmaUK Guest

    its more the shape of the chamber and is a function of both length and bore. you get some effect with a flare, you get more with a standard pipe and even more with a tuned pipe built for the motor. The problem is they have to be designed for the machine because of how they work. very basically they propogate the exhaust pulses back toward the exhaust to improve scavenging in the engine sorta like an inverted blower idea which gives you more power. However the problem with a single stage pipe is that it only gives this effect within a given powerband - get that wrong (ie 'going on the pipe' at 7400 rpm when the engine tops out at 7500) and its useless. A multi-stage pipe will have three different boost bands because of three different areas of the pipe helping scavenging at different speeds and therefore will have an effect through more of the power band. Its a similar idea to the adjustable plenums on some of the more upmarket fuel injection systems fitted to car engines only its at the other end..

    Jemma xx
  8. motoschwinn

    motoschwinn Guest

    Are any dealers left selling the poo poo?
  9. Gimmick

    Gimmick Guest

    a couple of thoughts, answers...etcetera. The "poo-poo" pipe is not an expansion chamber type pipe. it is simply a longer pipe with an unbaffled muffler section. It comes in two peices.
    I checked the plug and sure enough the pipe had promoted a lean burn condition, pretty unexpected being as i live at 6300 ft above SL. Returned the pin to the second setting and certainly found that last 4 mph. Still the pipe has greatly increased low end power. Hills I was pulling at 20 now are coming off at 24-25 mph.
    I think my next step is to replace my 50t sprocket with a 40 or 36.
  10. forrest

    forrest Guest

    Good deal with checking the plug and getting a little more fuel to the engine!

  11. gone_fishin

    gone_fishin Guest

    opinion: the lean is probably the boost you feel...carefully monitor your mix, go as rich at it will tolerate, play with the plug-gap also if you feel the combustion chamber is too "dry." if you don't have a slight "sheen" on the plug threads, it's likely the rings and cylinder-wall look the same....not a good thing.
  12. Gimmick

    Gimmick Guest

    resetting the needle did help. the plug is now back to the toasty brown color. I really think a different carb is appropriate for this thing. Also, I ordered the chrome steel manifold dax sells, I have the very restricted aluminum one now. Stay tuned for news of that.
  13. TNlightnin

    TNlightnin Guest

    Fixing the lean condition was good. Go another notch or two richer and you shud see more power since your pipe is flowing better than stock. Goodluck!
  14. CrazyDan

    CrazyDan Active Member

    Why is it guests and new members always revive ancient threads?