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Discussion Starter #1
K, so last year at the end of the winter i blew one of my piston skirts, being a cheap 17 year old i just put new pistons and gaskets in. So now about 250 miles later im starting to see some of the symptoms before it went last time again. And im sure the clearence is way to high. So i want to ride this thing and fix it right so off to the local sled parts store i go and get 2 new renaskiled pots, new pistons and gaskets and before i install them i want to ensure they will work good. i checked the cleasences and what concerns me is that the piston has about .020'' of movement at the top but about .0035 at the piston base. i like the .0035 but the .020 scares me, any opinions?

Oh and there spx pistons
 

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Get yourself a pair of new OEM style pistons, ship them and the jugs to US Chrome and have them check your clearences, and perhaps just coat the piston skirts?
 

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Discussion Starter #3
the cylinders are fine, but a straight edge on the piston shows a sudden decrease in size about 2/3 the way up. Im going back tommorow and probably going to get either oem or wiesco.
 

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I just fix 'em...
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There is nothing wrong with your pistons- they are much smaller at the top for a reason. There is more aluminum at the top of a piston and it will expand more than the bottom of the piston will when it reaches operating temperature. SPX is the same piston as SPI here in the states, nothing wrong with them.
Jerry
 

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When I first got my ZR500, it had just been rebuilt. Problem was, the (pro?) that rebuilt it put one of the pistons in backwards. The ring pin came off and destroyed the piston and cut grooves in the cylinder wall. Makes sure the ring pins go toward the intake, not the exhaust.
 

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Discussion Starter #6
yeah thats what i was starting to think about with the piston differences. But then why wouldnt the company tell you that somewhere
 

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Maritimes Guy
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Dont forget ring pins on intake side,not exhaust.Whoever worked on my sled before put one in right and the other backwards, the backward one's rings were hitting on the exhaust port and scratched my cylinder too.
 

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Discussion Starter #10
yeah im aware about how the ring ends need t o be in the proper way so not to grab a port. U should also mark on top of the piston where these pins are just to make dam sure its right. Ring end gap is also very important
 
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