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Discussion Starter #1 (Edited)
I spent part of Sunday and part of Monday honing a 71.0 mm cylinder (jug) to accept a 71.5 mm piston. I placed a 67 mm stock sized piston in the cylinder so you get an idea how much bigger the 71.5 mm is than stock. This should increase the displacement from 196 cc to about 223 cc. The bad news is this piston is only 8.7:1 compression ration. However, it is destined for my parts bike so who cares. The next step is to enlarge the case to accept the larger in diameter cylinder. BTW, the cylinder to piston clearance is .0026".

Stock piston:
PB160016 (2).JPG PB170016.JPG

71.5 mm piston:
PB160018.JPG PB170017.JPG

This is the hole in the case that needs to be enlarged about the width of the bevel around the edge. I am hoping to do it the way Ronnydog did, with a Dremel.
PB110016.JPG

Reports to follow as progress is made. If this all works well I have a 71.0 mm 10.25:1 compression piston for my primary TW. Tony
 

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Discussion Starter #2 (Edited)
Far left is dished low compression piston. Middle is domed high compression. Far right is cast stock piston.

PB160018 (2).JPG PB160017 (3).JPG


Edit: I showed this picture to Big D, The PBR, and he said that the cast, stock piston sure looks like crap!

The only TW that I know of that has a pretty Wiseco piston in it is Fred's -- hopefully that will change in the near future.
 

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The Wiseco piston is a thing of beauty by comparison. I especially like the numerous oil holes bored directly below the rings, I imagine they allow better oil splash through the piston skirt to lubricate higher on the cylinder wall at the top of the stroke.
As far as performance goes Adam and I traded back and forth for comparative purposes and we both thought that my bike accelerated a little better despite heavier ATV tire. I experimented with 89 octane last weekend and felt perhaps I was getting knocking some ten seconds into a very steep sustained hill climb @ ~6500 ft, 70 degrees F, pulling hard in 3rd. I backed off and finished the climb at a more sedate pace in second without any more unusual engine noises.
Now I will probably have to grow used to feeding that 10.25 :1 compression ratio 91 octane. My POL dump already has diesel, two-stroke, and 85 octane for the ranchero life ( love my 4-stroke line trimmer..lots of off-idle torque for quite trimming while Mrs. Fred sleeps in) so what is another fuel jug?
 

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Discussion Starter #8
As far as performance goes Adam and I traded back and forth for comparative purposes and we both thought that my bike accelerated a little better despite heavier ATV tire.
I can tell a definite difference between my stock motor and my gf's bike with the wiseco piston in it. Hers has more power for sure, riding both back to back numerous times has confirmed that for me.
I like positive results. Glad to hear it.

I can't really tell, I haven't rode my bike bike since late last fall. I will let my buddy ride it and see what he thinks compared to his.
Report back when you find out. I will be interested in the results.
 

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Reviving an old thread! What kinda work and cost is required to go from stock piston to this wiseco beaut? Honing the cylinder and what about the valves and top
End?
 

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Discussion Starter #10
The cost of the piston -- search ebay and you might get lucky -- around $100 and then have a machinist bore or hone the cylinder -- $50 to $100. Get a complete gasket set off ebay which cost about the same as a new head gasket and base gasket -- about $40. The TW head itself works fine but you will need a 225 head gasket because of the larger bore.

I bought a cylinder hone for about $150 so I could enlarge the cylinder myself. You will also need the right micrometers and know how to use them, a good slow speed electric drill, and a ton of patience (patients ????) if you go this route.

I never got around to using my 71.0mm or 71.5mm piston or cylinder.
 
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