PK80 Ripper from BMW

gary55

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Joined
Nov 27, 2012
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Location
Prescott, AZ
I got my orders in from BicycleMotorWorks, and shot a email to Matt to ask him if he minded me reviewing his Ripper engine. He said go for it so here is what I have so far. Still need a few more details so their will be more to come. these numbers are mms down from top of jug.
Ripper engine. = PK80 with fat crank cheeks 19mm compared to the 17mm Zeda cheeks. Long stroke short rod A type with ported G4 jug.
Exhaust 28.2 and 28mm wide
Transfers 34.6 This 6.4mms of blow down is reduced to 4.4mms because the piston is ramped about 2mms at the transfers with no ramp at the exhaust.
Intake 45.5 to 58.9 and 26mm wide
It has a .2mm copper head gasket with a single base
Head is a 6cc chamber with the only drawback being the crush ring ID is 43mm. Easy enough to fix.
The top of the jug as well as both port flanges are surfaced exhaust porting is smooth intake is just a little rough just how we like it.
Don't have the squish gap yet. More to come.
I imagine some of you guys out their could figure what the port mapping is on this engine in degrees, but not me.
Pics. of Ripper compared to stock.
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I just print them off the internet and glue them to a CD.
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Here are some calculators that don't involve, well you know. A warning may pop up but it's safe. Ni degree wheel needed. Thanks goes to Streets and Chris.

 
How does the case casting compare to zeda or cdh?
So close to the same it's hardly worth mentioning accept the front mount is still the narrower style like the old ones use to have. It does have the 8mm mount studs. The clutch cover has the sharper edges like the old ones rather then the more rounded edges like the Zedas and CDHs.
 
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