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Discussion Starter #1 (Edited)
I read A Graham Bell's 2 stroke tuning book and it inspired me to make a custom exhaust and go port the shit out of something, problem is im pretty sure i would screw something up my first time and i surely dont want to practice on a machine that i actually care about... so i dug the old qt50 out of the corner of the garage, that turds been collecting dust for over a year. anyhow hears what i came up with, looks pretty goofy, my only goal is to make it sound like a 2 stroke and have a power band.





for the porting i only messed with the intake and exhaust ports, and just smoothed the transfer port runners. the exhaust port i hogged out allot, probably 50% more volume and i raised it a little as well. i made the intake about 2-3mm wider on each side and opened up the runner a bit.





if you don't know what a qt50 is, its a moped... its possibly the gayest looking 2 wheeled machine a grown man could ride. that 50ccs of 2 stroke fury will push me to about 28mph, if the wind is right. same motor as a pw50 (you know, yamahas smallest dirt bike, for like 2-4 year olds)

just something to tinker with when im bored.
 

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that's cool:) I got a moped myself that I use to and from work, a -93 Honda PXR50 with a performance exhaust and a whopping 60cc bigbore kit, it does 80kph on a good day:)
 

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Discussion Starter #3
so thats like 50ish mph huh, thats pretty darn good. does it have any type of transmission, i know Honda had an auto 2 speed on some of there mopeds? mine just has a single drive gear with a centrifugal clutch, i lightened the clutch up and put some stiffer springs in it so hopefully it stalls high and snaps in hard.
 

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It's a single drive with centrifugal clutch like yours, mine has a worn drivebelt and stock clutch spring so it's a bit sluggish on take off, gonna drop in a stiffer spring and a fresh belt soon though.

here it is:
 

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I've been reading the Graham bell 2s book also, it is definetely a in depth book and if you are enthusiastic about wanting to aquire more knowledge how a 2 stroke engine works along with different port configurations/tuning its definetely a good one to read.

Pipe looks great btw!
 

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so thats like 50ish mph huh, thats pretty darn good.
Im not sure but for some reason I thought it was closer to 30mph.

Fun looking ride tho




EDIT: Dude, that pipe is awesome.
 

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Very impressive. Pipe building is a very fine art, most would never attempt. The math involved is intensive, way more so than just porting figures. Keep up the experimenting, thats how these engines got to where they are today
 

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lol and for us lazies there is java pipe to do the calculations for us :D

i used to make RC boat pipes
 

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HillClimb/DirtDrag Champ
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very cool man! i give you props for experimenting like that! keep us updated...maybe some vids if you can in the future!
 

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Discussion Starter #11
thanks for all the replies, didnt think it would get this much interest.

hears a pic of the pipe design i layed out on autocad.





the only thing i wasn't sure on was what rpm she will run at, i have the pipe set at a tuned length optimum for 6500rpm - 1000rpm higher then stock. if i can get a tack hooked up to it and see if it goes higher i can shorten it up, i went ahead and did the math for tuned length at different peak rpms and drew those up on cad as well for reference if i want to shorten it.

if my piston gets here for it tomorrow i will get some videos.
 
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Discussion Starter #12
this was also good welding practice for me, i just bought a pos mig for $50 about a week ago. now that i finally have a buzz box there's no telling what creations im capable of lol.
 

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Im not sure but for some reason I thought it was closer to 30mph.

Fun looking ride tho




EDIT: Dude, that pipe is awesome.

Man that is a good lookin LT you got there. You should start a picture thread for it.
 

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thanks for all the replies, didnt think it would get this much interest.

hears a pic of the pipe design i layed out on autocad.





the only thing i wasn't sure on was what rpm she will run at, i have the pipe set at a tuned length optimum for 6500rpm - 1000rpm higher then stock. if i can get a tack hooked up to it and see if it goes higher i can shorten it up, i went ahead and did the math for tuned length at different peak rpms and drew those up on cad as well for reference if i want to shorten it.

if my piston gets here for it tomorrow i will get some videos.
sweet!!!!!
 

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be sure to shoot a video of you testing it, the pipe I got on my PXR50 really does nothing for power, it looks and sounds the part, but compared to the stock "can" it's about equal. and what makes the biggest powergain for me wasn't the extra 10cc, but the much bigger ports, the bigbore cylinder got something like 4 ports more than the stock.
 

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Looks like fun. Sick work on the pipe, as the book says "You never get it right the first time" (or at least along those lines.)
 

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Discussion Starter #17
yea, i am positive something about it isn't going to run right. the fact that i messed with the ports kind of bothers me since i have no experience with it, i didn't go that crazy with it but the idea of it just makes me a little uncertain lol. as long as it doesn't sound like a chain saw and goes at least as fast as it used to i would call it a success for my first shot.
 

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Let us know how it works out for you! We pay 100's for aftermarket pipes!
$50 welder + cad access are great tools to have. Nice work dude!



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Tell you what, for a first pipe, I'm impressed!
Especially rolling the cones. I would figure the first attempt at rolling a cone would look like it was in a hail storm! Nice Job! keep us posted on how it works.
 

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Discussion Starter #20
yea i was worried the cones would come out like crap but it was easier then i expected, just takes patience. hopefully my piston gets here tomorrow, im very curious to see how it runs.
 
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