Ive rebuilt several Polaris two strokes and noticed that when using Namura pistons, they definetely have more chatter going on. I tried WSM and it was even worse. I thought the first time it was a bad bore job, but this last rebuild, was perfect and still noisy. I give them the piston and have them cut the cylinder to fit it and still some racket going on. Polaris stock pistions are nice and quiet. I havent tried Wiseco, since I was a kid. I think I will try Wiseco on my next rebuild. I am not a big fan of forged pistons, I prefer cast, more like factory. Anybody else notice this? Namura makes a nice looking piston, no trouble except this, just sounds like piston rap.
Noisy pistons
- Thread starter Panzerman
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forged pistons expand more than cast piston so they require more wall clearance...yes this makes them noisy when cold which is why it's a good idea to get the engine to operating temp before a beating...nothing wrong with forged pistons, in fact the only drawbacks are the noise and maybe cost
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Originally Posted By: Panzerman
I am not a big fan of forged pistons, I prefer cast, more like factory. Anybody else notice this?
Panzer, I am assuming that you have a reason for forged versus cast (NOS or some other HO application on the engine)?
You may want to see if any of the manufacturers offer hypereutectic pistons--these are (more or less) between cast and forged with regards to strength and noise. Hypereutectic pistons can run closer tolerances and thus less piston noise when the engine is cold.
Hope this helps!
I am not a big fan of forged pistons, I prefer cast, more like factory. Anybody else notice this?
Panzer, I am assuming that you have a reason for forged versus cast (NOS or some other HO application on the engine)?
You may want to see if any of the manufacturers offer hypereutectic pistons--these are (more or less) between cast and forged with regards to strength and noise. Hypereutectic pistons can run closer tolerances and thus less piston noise when the engine is cold.
Hope this helps!
We used to upsell forged pistons for everything when I worked in a machine shop back in the day (talking late 80s here). Heck we'd send 'em out in 350s that went into Caprice station wagons. Never had any noise complaints, but then again we also sent everything out with Valvoline conventional 20w50, too.
Ahh the good old days
OK, all that aside, I'd use factory pistons too, nowadays.
Ahh the good old days
OK, all that aside, I'd use factory pistons too, nowadays.
I participate in some forums related to vintage two cycle motorcycles (Yamaha RDs, Kawasaki H1/H2 Suzuki etc.) Namura pistons are not well received.
OEM, Wisco and Pro-X are the pistons of choice. Personally, I use Pro-X. Not sure if you can get them for a Polaris but it might be worthwhile to look into it. I buy complete piston kits (piston, wrist pin, wrist pin bearing, circlips) for around $85.00.
OEM, Wisco and Pro-X are the pistons of choice. Personally, I use Pro-X. Not sure if you can get them for a Polaris but it might be worthwhile to look into it. I buy complete piston kits (piston, wrist pin, wrist pin bearing, circlips) for around $85.00.
I like the cast pistons more for the durability and the fact they are what is in the stock application. The Polaris's arent really high performance, although I jacked the rpms up in the one, just to see if the Namura holds together. Very nice looking pistons, but I know what you mean, I read love hate respones on them. Time will tell. I think I may spring and try the Wiseco next time. I dont think Pro X is avaiable and Athena, does not look any better than the Namura. The WSM pistons didnt impress me at all. That Teflon or whatever they put on the sides is a joke, I tore one down after about 100 hours and most of it was gone and it was just a plain piston. After a year, you cant tell it from a stock one.
OK, I'll ask...what clearance are you running? 2 stroke engines aren't that common and not all machine shops make a good hole.
Originally Posted By: Smoky14
OK, I'll ask...what clearance are you running? 2 stroke engines aren't that common and not all machine shops make a good hole.
Two stroke engines are common enough if you know where to look.
I live in the north where snowmobiles are common in winter as are their two cycle engines. During the summer, outboard motors and PWC engines are prevalent.
We have a specialty shop that works with two cycle engines all the the time. In summer, they work on PWCs and outboard motors. In winter it's snowmobile engines. That's where I take my vintage Yamaha two cycle engine cylinders for work. They do a great job.
Being that the OP lives in Florida, for cylinder work, I'd be looking for a reputable engine shop that caters to the PWC/outboard motor crowd.
OK, I'll ask...what clearance are you running? 2 stroke engines aren't that common and not all machine shops make a good hole.
Two stroke engines are common enough if you know where to look.
I live in the north where snowmobiles are common in winter as are their two cycle engines. During the summer, outboard motors and PWC engines are prevalent.
We have a specialty shop that works with two cycle engines all the the time. In summer, they work on PWCs and outboard motors. In winter it's snowmobile engines. That's where I take my vintage Yamaha two cycle engine cylinders for work. They do a great job.
Being that the OP lives in Florida, for cylinder work, I'd be looking for a reputable engine shop that caters to the PWC/outboard motor crowd.
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