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Old February 15th, 2012, 04:22 PM   #8
FrugalNinja250
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Name: Frugal
Location: Dallas/Fort Worth (DFW)
Join Date: Mar 2010

Motorcycle(s): Several

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Quote:
Originally Posted by Skippii View Post
Okay, I should have clarified that a bit. The options are to replace and hone just the one cylinder/piston/rings with OEM, or to replace and hone both of them (possibly with aftermarket.) Which is basically exactly what you said.

Main question is, is it worth replacing the piston that still works fine and shows 170psi?
Pistons don't really wear out, per se. What wears is the ring/wall interface. If you replace just the one piston the main issue you might have is a little more vibration from the new bore having slightly better ring sealing. Might. The other piston, if the rings are sealing well and it's not damaged, will be just fine. What happened to the piston that failed was a problem with the carb on that cylinder, not an overall engine problem. Since the Ninjette doesn't use a shared manifold intake system problems are more limited to just the affected bore, unlike something like an airplane engine which may have a single carb feeding multiple cylinders. Also, unlike airplane engine you don't have to rebuild the engine perfectly to meet any FAA regulations.

You can if you want to, but that will get expensive quick, and IMHO isn't really necessary unless you were racing.

I'd just replace that piston, and in fact, if the rings are good and it was my engine I'd leave the original rings in, they're already match-worn to the cylinder wall. But my labor is free to me so I wouldn't have a problem with popping things back apart to replace little bits like pistons.
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