rough puch tuning info... port open, rpms, etc

yo. ive been kicking around the idea of making an expansion pipe from the ground up, starting with all the calculations. i prefer motobecane over puch, but i dont wanna have to tackle a ball joint and crazy moby mounting and such for my first pipe... so im doing one for a stock puch maxi. i dont even own a puch right now (my friend's bike will be the guinea pig), so i figured some of yous dudes would have some info for me.

im just looking for some rough info that you might already have written down somewhere for a couple things: first thing i need is port open duration of a puch stock cylinder. rough idea is fine, port height is fine too i can take it from there. anything you got. next thing i'd need is a basic idea of where the peak RPMs would be for a stock puch maxi 2-speed. cant get it w/o a tachometer, and i can calculate it via mph and gear ratio and such but i dont feel like that's as accurate. it'd be good to have an idea of what other people have already measured.

i just want a basic idea of the proper numbers so i can mess around with plugging them into jennings' formulae and whatnot. this way once i get the actual data from the bike i'll actually know what to do with them, and i can just plug and chug. think of it as a practice round.

thanks for the help,

-Steve

Re: rough puch tuning info... port open, rpms, etc

Wouldn't you want to tune it so that it would work with stock and kitted bikes? They are all different...

Re: rough puch tuning info... port open, rpms, etc

Stock exhaust timing is about 150 degrees. A properly tuned stock puch will go about 30 mph or so with 15/45 gearing so a little over 7000 rpm.

Check out the wiki for porting and calculations. Japps Puch calculator is awesome! too bad you have to use the metric system...

Good luck,

Eric

P.S. A two stroke will rev way higher than 7000 with some porting and the right exhaust. With just porting and a jet change, I made a stock cylinder go from 20mph(1hp) to 38mph. Don't forget to upjet.

Re: rough puch tuning info... port open, rpms, etc

i dont particularly care for it to work for kitted puchs because i dont have a kitted puch and i dont plan on having one. i dont even really care for puchs... if i could make a moby pipe as easily as a puch pipe then id be doing that, but its not so easy. like i said im gonna try it out on my friend's puch and if it works he can have it. this is pretty much just for the hell of it, if it works it works if it doesnt it doesnt.

i guess there are probably different puch cylinders with varying port open durations and such, so the best way to figure it out would be to get in there and measure myself...

thanks for the link eric, i didnt see that earlier... very helpful. dont forget to upjet... haha... thanks.

-Steve

oh another thing i just realized, its a maxi w/ a za so i didnt think about what the different internal gearings are. looked through the shop manual and didnt find it... anyone?

Re: rough puch tuning info... port open, rpms, etc

bump.

Re: rough puch tuning info... port open, rpms, etc

Sounds like a fun project...

Re: rough puch tuning info... port open, rpms, etc

Right... This information is WIDELY AVAILABLE, I promise. Use the search feature, the wiki or hell, crack a book.

Re: rough puch tuning info... port open, rpms, etc

theres a article in the wiki with dimensions of most puch pipes.

Re: rough puch tuning info... port open, rpms, etc

I don't know but my stock gearing on my za50 magnum is 18front 40 rear

Re: rough puch tuning info... port open, rpms, etc

Just read all the stuff available on the subject, Jennings, Blair, Bell, Foekema, then you'll be able to calculate a real good exhaust for the ped you prefer, get's you a lot further than just trial and error really.

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