Piston Mod Drawing for 175 Complete

[Chakka]

I took the time to measure the piston out of my Jackpiner which has been modified for a GEM reed valve. I produced a drawing in AutoCAD with all the measurements. I would like to share the file by posting it to the Penton Tech site on Yahoo. What format is prefered on that site, probably .PDF?

Chris

[john durrill]

Chris,
 any type file will do as long as most people have the software to view it on a machine. Try and get it large enough in size(500k usually works )that the words and #'s are clear when the file is downloaded and viewed. Thats hard to do sometimes  if the original was scanned at too low a resolution.
 Post them and let a few of the folks give us some feed back on how it looks please.
John D.

[Steve Minor]

Chris....I do alot of AutoCAD too and (in my opinion) I think a PDF format would be best. One reason is a free PDF reader is available from Adobe Acrobat on their website...



Steve Minor
Wilmington, NC

[Chakka]

I posted this drawing in PDF format for anybody who needs it.

Steve, I think your right. The standard images AutoCAD puts out, .tif, .jpg are terrible. I have drawn up a number of Penton parts. Now if only I could find a local fabricator to do small run parts....

Chris

[john durrill]

Chris,
 That worked great. That is a different pattern on the piston from the 2 kits we installed ( per Gems instruction sheet ). The bottom holes are elongated and the 2 top holes are added. That looks like a better set up.
 I did some reading on reed designs since 91 ( 2nd Gem kit we did on a 175 KTM ) and found that 240 to 260 degs intake duration is supposed to be ideal.
 The elongated  bottom holes and the added 2 top holes are what is done to extend that when the reed adds too much restriction to the intake track. That would let  a smaller 2 petal design like the Gem kit work better on the Piner engine.
When we did a kit on the Ace100/ Super Rat, I liked the 4 hole pattern. That was what Hodaka recommended. I thought the 2 top  holes were for keeping the piston crown cooler. Thats was the main reason Hodaka went for the 4 hole design.
 Now i believed  it served 2 purposes . The added cooling to the piston crown and increasing the ability of the engine to flow enough air with the 2petal cage in the intake tract .
 Adding a 2 to 4 mm bigger carb would be a good idea . That seems to make the kits easier to jet.
Thanks for the drawing.
John D.

[tofriedel]

Chris,

Where did you post your pdf file?  

Thanks,

Tony

[Chakka]

Thanks John,

Glad it came though alright and the resolution is good. I'm also glad to here this piston mod could yield better performance than the suggested GEM mods. Any time the group needs CAD drawings I would be happy to make them. I have plans for a Center Stand for 74-76 Enduro models done and am working on a drawing for a 175 kick starter shaft so I can have one made locally.

Tony, follow the link pasted below:

http://autos.groups.yahoo.com/group/PentonRestorationandTechGroup/files/