Pocket bike tuned pipe build

[ANDREW]

Hey guys i am going to try to make a pipe like noiseguys here is the link for the site for the pipe i am going to use. It looks like the inner diameter will be bigger than the stock spree's 19mm that is just a guess though, It says that the hole are 1.5'' apart witch is bigger than the spree so i assume that the inner dia of the pipe will be bigger. The downpipe is 10" so i am gona attempt to re bend the pipe to fit the spree and make a manaflod so that it will bolt up to the spree's cyl.
let me know what you think and if you think it will work.
Andrew
http://www.pocketbikeparts.com/Exhaust_p/cgex301486.htm

[ANDREW]

I forgot to say that i am going to port the exhaust two ring widths also.

[mookie]

i used,from the looks of it, the same one on my Spree.
it feels like IF the motor could rev out farther it might make some power.i saw 32 mph once when i was holding my mouth just so so...

DO NOT attempt to simply "bend" the header pipe. it will collapse.
yes you will need a Spree manifold and depending on whether it is a low boy or high riser some additional pipces (pipe pieces) will be required...

[ANDREW]

cool looks the same but maybe you need to cut it in half and add a center section to adjust the tuned length it explained it in the jennings book i will prob add a center section to mine and experiment with it as soon as i figure out what just happend to my spree i was riding today and the rpm started to drop then it just stoped i was riding at WOT when it happend and now when i kick it over with the plug out it dose not sound healthy i am going to post somthing in tech section.

[mookie]

ouch! sounds like it seized.
cool weather=lean
warm weather=rich

[tazland001]

did you upjet when you put that muffler on. Just curious? do you have the 44mm BBK on that scoot?

Taz

[mookie]

naw it's bone stock otherwise- wanna donate a BBK towards the effort??

[capturedbyrobots]

I used a goped pipe welded to the original header of my converted Yamaha Jog into a standup.

Did a little reshaping, but it works great.
I bet it would even fit under your fairings....
It was a Bladez pipe.

[ANDREW]

Im not going to use that pocket bike, pipe im getting one made for me from a sheet metal guy then im welding it up, i used the tuned pipe calculator and i am porting a 86 cylinder i will have this all done by June i will let you guys know what kind of speed ill be seeing.

[elitedio]

If you haven't you might read Jennings's book. It was written a long time ago but the info is still relevant. It is out of print but noise guy posted a link on this site. There is also kart engine software by iwt racing. They have a free version and a different for sale version.

I started with these tools as well as the link that you provided and ended up reverse engineering a moto-cross pipe with good results. I was amazed that each software and book provided different lengths, diameters and tapers. Obviously they are using different algorithms.

Look forward to seeing what you come up with.

[ANDREW]

I have two differnt designs one for the ported cilender and one for stock cyl i think i will make the stock one it would prob run very well with a ported cyl.

[ANDREW]

Here are the pics of me makeing the paper version so i could get an idea how big it would be.
Its pretty skinny but it is done acordind to the calulations i will start rolling them tonite maybe.
this is without the head pipe
sorry the images are massive i cant resize them

[noiseguy]

If you haven't you might read Jennings's book. It was written a long time ago but the info is still relevant. It is out of print but noise guy posted a link on this site. There is also kart engine software by iwt racing. They have a free version and a different for sale version.

I started with these tools as well as the link that you provided and ended up reverse engineering a moto-cross pipe with good results. I was amazed that each software and book provided different lengths, diameters and tapers. Obviously they are using different algorithms.

That's not surprizing; those algorithms are empirically (experiment) based on best results from cutting and welding several (probably dozens) of pipes for different engines. The results are all thrown together into a multivariate modeller and wa-la! New pipe equation.

Every tuner that does this has a different set of results that they start from, so they won't look exactly alike, but they'll be close.

They are not based on first principles and thus won't match. But that's just fine; the results are close enough for what we're all doing. And a close-form solution, like that, probably wouldn't work any better.

I did this exercise once and created a paper model that looked pretty much like the one above, so you're on the right track. I even made a wood positive to form cones around. After messing with it a bit, I said, "meh, too much headache" and built my pipes out of pocketbike parts. Much easier, cheaper, faster results. I was building to sell in addition to the ones I made for my bikes; the people that were willing to pay for pipes were not willing to pay enough to compensate my time for a full custom. And the pocketbike pipes were a marked improvement, anyway. So I built them that way instead. If I'd tried rolling them, I probably never would have finished the project.

[ANDREW]

Ya i made a positive mold like you did but it reall did take a long time to roll the cones properly.i have two brand new pocket bike exhausts that i will screw around with.
I will tell you guys what i come up with and i will post pics.
Andrew

[madskater1987]

Ok I built one, It's not real pretty but it only cost about $15 for the parts.

It helps mid range to top end alot