Cast or forged?
- Thread starter MARV1
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I don’t know anything about pistons but I know Indy Specialty a trusted Polaris engine builder says oem only for Polaris. You might give them a call they are very helpful
I know all about Indy specialty
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It doesn't really matter, especially for a 650, as long as you buy a well known brand, like Wossner or Wiseco or OEM, etc. Just be sure to let forged pistons warm up before you hammer on them. Same for cast, technically.
At the miles you're at, I'd fully inspect the crank, spin test the bearings and do a leak down or simply replace the seals. Would also check the exhaust valve lands to assure proper clearance.
At the miles you're at, I'd fully inspect the crank, spin test the bearings and do a leak down or simply replace the seals. Would also check the exhaust valve lands to assure proper clearance.
Inquiring mind! Have to see what others thought. Yes lots of miles on it but ran damn good everyday. I was hoping the Wossner kits would be dual rings like the 850 but they aren’t.
I’ve had good luck with Wossner and Wiseco but they both don’t have dual rings for the 650. If dealer doesn’t get me stock ones I’m most likely going aftermarket. I see that MCB has cast and forged options
I ran Wossners on my Pro for a season, but noticed abnormal wear patterns in the vicinity of the locator pins (no other indications of trouble and they had plenty of gap; my best guess is the pin end of the rings were fluttering). The OE pistons were hard to find at the time, or I would have gone with them initially. Later, since the cylinders were no longer pristine (they were redone before the Wossners), I decided to just try some aftermarket cast pistons and see where it went. So I went with SPI hyperdrive pistons - a very close replica of the OE piston. I only have one below average season running those, but no issues, and others say they're good. In hindsight, I wish I'd dug a little deeper for OE pistons to begin with.
I don't think you're going to beat the OE piston here, and 7900 miles pretty well proves that point. I think there are decent aftermarket pistons, but I don't see any reason to go with them other than saving money (and I doubt Polaris's cost justifies the price). At that mileage I'd have some concerns about the crank, however, and I've been told the 650/850 cranks are hard to get apart and back together cleanly, unlike the old Fuji cranks. If runout is getting excessive or the bearings seem sloppy and you don't feel like investing in the sled for the long term, I'd say put the cheapest thing you feel comfortable with in and go with it. Then again, I haven't heard of many 650 cranks grenading, so maybe you could get thousands more out of it - just something I'd definitely check over. It's a similar position to my old 600 (that with a few less miles) that's probably due for pistons; when I do that, I'll go with OE if everything looks good when I tear it down.
I don't think you're going to beat the OE piston here, and 7900 miles pretty well proves that point. I think there are decent aftermarket pistons, but I don't see any reason to go with them other than saving money (and I doubt Polaris's cost justifies the price). At that mileage I'd have some concerns about the crank, however, and I've been told the 650/850 cranks are hard to get apart and back together cleanly, unlike the old Fuji cranks. If runout is getting excessive or the bearings seem sloppy and you don't feel like investing in the sled for the long term, I'd say put the cheapest thing you feel comfortable with in and go with it. Then again, I haven't heard of many 650 cranks grenading, so maybe you could get thousands more out of it - just something I'd definitely check over. It's a similar position to my old 600 (that with a few less miles) that's probably due for pistons; when I do that, I'll go with OE if everything looks good when I tear it down.
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The latest SnowTech is showing a list of quality changes Polaris made to the 2025 sleds. It's the list we all would like to see at Snow Check time but Polaris never lets us in on. The first thing on the list of powertrain updates for both the 650 and 850 engines is new pistons for improved heat transfer for improved durability. Perhaps this would be a good option for your rebuild.
