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Piston out of bore safe distance


Ollies930

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Does anybody know what the maximum safe distance is, that a Wiseco 573M06800 (68mm bore for 5mm longer rod) can stick out of the bore, before the rings start to snag on the top edge of the cylinder? If I remember correctly, the ring lands are 3.5mm down from the crown. Not one hundred percent sure though. Any help is appreciated, thanks.

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With pistons sticking out 2.5mm the intake is 131 and the exhaust port is 198. The intakes are where they were from the factory, just a bit of radiusing of the edges and I raised the exhaust main port 1mm to open it before the boost ports. If I could let the piston come out another .015" or .38mm, then the exhaust would end up at 196.6 and the intake would be at 129.2. It is quite peaky right now and has very little power down low, this should help a bit. 

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thats the problem when you put longer stroke crank in some cylinders. the timings go goofy and theres not much you can do. im doing the same thing with 82mm crank in a 80mm stroke cylinder. there wont be near as much grief as yours but still ill have to put the cylinder at a certain height for it not to be a big fuggin mess

 

Sled?

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not exactly. its ktm with honda rod and piston. waiting on material that should be here friday so i can make a spacer plate. the plate with various thickeness gaskets will offset the difference in rod length and wristpin height and set the window heights at a decent starting point for the porting . ill have some pics when i get a chance

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