Expansion Chamber

This summer I am hopefully going to be designing and constructing an expansion chamber for my Honda PA50. I know that it would be a lot simpler to buy one, but I want the experience, and I also don't want to invest too much money into a moped that I got for free.

The one thing that I need to know to construct one is about many rpms my engine will be running, and I was wondering if anyone coulld tell be about the range of RPM's a SLIGHTLY ported PA50 would be running.

P.S.- for anyone wondering.... I am getting the formulas to calculate the size and shape of my expansion chamber from this website.... http://microcarproject.tripod.com/html/expansion_chamber_design_softwar.htm

Re: Expansion Chamber

buy or borrow a tiny tach and then you'll know for sure exactly what and when your rpms are what they are.

Re: Expansion Chamber

Raymond Rexroad /

The 1983 Shop Manual shows that a PA50II motor spins at 5500 RPM at 27 MPH.

How fast are you wanting to go? Once you have that number, you could calculate engine RPM. Also - if Malossi gears were in the plan, this would shift your RPM value as well.

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Yeah, is was gonna say about 5500 is the industry standard. My suzuki says something like blah blah blah 80decibells at 5500 blablahblah conforms to blahblah blah regulations.

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Yeah... after I posted this I looked at what it would take to do 40 mph with the specs that are in the shop manual I have... about 10,000 rpms. This seems pretty high up there, but I think that it might be pretty attainable because my uncle said that it used to do 35 stock... for those of you wondering, he was pretty light, but then again so am I.

I have pretty much decided that I am going to stay with the stock cylinder, and just tune it. I don't want to invest much money in it because I got it for free, and I am also saving to buy a car gasp and the this is just going to be a toy for me to play with.

I am interested in those malossi gears though... where could I get a set of those?

Re: Expansion Chamber

if you hunch down and a little bit of a hill or wind that is easily possible

Re: Expansion Chamber

hah, i have a car, and i'm saving for mopeds!

Re: Expansion Chamber

you're definately not working that out right, no way is 40mph 10,000rpm...stock it will rev to just over 5000rpm as everyone else is saying

Re: Expansion Chamber

lee's anus is leefungchowOG /

40 is probably around 8 thousand.

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yep, i work it out at 7819rpm, using the OD of the tire as 21"

Re: Expansion Chamber

want to build two? :D

Re: Expansion Chamber

seeing as though you can get to almost 40 with just the proma circuit pipe, which as we've just discussed is about 8000rpm, you should easily be able to get to 8500rpm just by porting the cylinder a little.

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The biggest problems you will have in designing the pipe are how to clear the pedals and how to clear the centerstand.

Re: Expansion Chamber

Yeah.. that will be tough. I might just end up routing it right around the cylinder like a proma, but I'm not sure yet.

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