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Unread 12-07-2019, 03:38 PM   #1 (permalink)
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Default 2012 rush top end

My 2012 rush 600 has 3000 miles on it, I was cleaning the exhaust valves, so I looked at the rings, and I noticed the top ring grooves were pretty large. I was able to fit a .015" feeler gauge in the groove. Everything I can find online specifies a .001" to .003" clearance for this measurement, or something similar. Does this also apply to 2 strokes? I read a lot of threads about how the pistons in these are junk, so im leaning towards replacing the pistons before something bad happens. Havent done a top end in a sled before so im wondering if I should expect the cylinder to need any servicing. I'm leaning toward cast pistons because i cant always guarantee that it'll get warmed up properly every time, but id probably want something different than the stock pistons if they only lasted 3000 miles.

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Unread 12-07-2019, 06:17 PM   #2 (permalink)
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Got 90 psi on each cylinder, not sure if I trust the tester I have though. Seems like it turns over easier than it should. Is it even safe to ride this season or should I do the top end now? I dont do anymore than 1000 miles in a season

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Unread 12-07-2019, 06:40 PM   #3 (permalink)
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If its truly 90 and the top gap is way wider than the bottom it needs pistons.Ive been using a lot of prox piston kits lately with good success.
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Unread 12-07-2019, 07:25 PM   #4 (permalink)
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yup, just waiting for a problem. Top of piston will knife and you'll have issues that require more than just a top end rebuild. Freshen it up with some SPI and you'll be good to go. Check your cylinders for scratches or chips. Get a proper piston to cylinder clearance from a machine shop. Top end gasket kit will be needed too. Not that hard to do, just take your time
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Unread 12-07-2019, 07:58 PM   #5 (permalink)
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Quote:
Originally Posted by Lexuslover View Post
yup, just waiting for a problem. Top of piston will knife and you'll have issues that require more than just a top end rebuild. Freshen it up with some SPI and you'll be good to go. Check your cylinders for scratches or chips. Get a proper piston to cylinder clearance from a machine shop. Top end gasket kit will be needed too. Not that hard to do, just take your time
So can I just bring my cylinders and new pistons to a machine shop to have them checked out without the rest of the motor? What should I expect to pay?

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Unread 12-08-2019, 12:27 AM   #6 (permalink)
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yup, you can do that. It doesn't take long to get the measurements, so i'm sure if you flipped them $20 as good will, it would be more than enough.
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Unread 12-08-2019, 06:25 PM   #7 (permalink)
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Anything else I should do to it while its torn down this far?

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Unread 12-08-2019, 10:22 PM   #8 (permalink)
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Fuel filter. Give the clutches a good inspection, replace both springs, and I would suggest running upper cylinder lube/injector cleaner through it in every tank. Sea Foam, Marvel Mystery oil, Lucas Upper cylinder lube and injector cleaner, etc. It's cheap, and it helps longevity.
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Unread 12-09-2019, 08:31 AM   #9 (permalink)
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I take my cylinders into my machine guys and have them measure/prep the cylinders and order the pistons for me. Easier for me and they order what it needs.
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Unread 12-12-2019, 08:22 PM   #10 (permalink)
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So what do you guys do if the clearance isnt right? Return the pistons and try another set? Sent the cylinders out for honing? Either way that cant be cheap. There should be some better tolerances on this stuff. I really doubt Polaris "adjusts" every motor. Can we just stick with OEM and not worry about it? Seems these motors are lucky to get a few thousand miles an engine anyway
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