Rotax piston ring info

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Postby lazflyn » Mon May 30, 2005 3:36 am

Hey guys I was doing a top-end overhaul on my Rotax's and noticed something that I haven't read or heard about yet. Maybe this is common knowledge to the more experienced guys, but for those of you like me who are learning about your engines, this might be helpful:

I needed to replace my rings to get my compression back up. I opened up the Wajax manual and got the part numbers for the rings. While I was at it I decided to replace all the gaskets as well since a few were starting to leak. The manual shows two different rings. An "L" shaped ring (part #R-331-1) for the top only and a "standard" shaped ring (part#R-331) for the bottom.

At the time I ordered, I hadn't pulled the rings off the piston. When I did, I noticed that the top and the bottom rings on my engines were identical. I find that interesting since that special "L" shaped top ring cost me 40 bucks and the lower "standard" ring cost me 8. So what is up with these 40 dollar rings? Couldn't I have saved some money if the engine runs great with a set of "standard" rings?!!

I called up Wildfire and asked for Charles. He rebuilds the pump version of the Rotax 185. I asked him what the "L" shaped ring is designed to do and why my engines don't have them. He said that the "L" shaped top ring is an upgrade and is designed to carry oil better to decrease wear and maintain compression. The reason my engines don't have them is because that is the way the factory makes the engines. They put two "standard" rings in there to save money. The "L" ring is basically a factory upgrade.

I am currently seating my rings now. Hopefully all this work will pay off in higher compression and some higher RPM's. Last year my engines ran great, but one engine was a little weaker than the other and as such I had to settle for reduced power since I had to sync them.

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Postby jb88ci » Mon May 30, 2005 12:40 pm

the L shaped ring is the same as a rotax 377 ring. They were designed for the new piston etc, as you have found...what kills me is the price of this stuff. I just got off the phone with Wildfire re: Gaskets...$12 for head gaskets and $7 for those flimsy cyl base gaskets. They also have a $50 minimum order....geez.
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Postby Guest » Fri Jun 03, 2005 10:16 pm

Not to throw a curveball into you guys discussion but rings also come in a thick and thin versions. Oversize pistons can have "thicker" rings than regular pistons.

Postby gdewsbury » Wed Jun 08, 2005 12:09 pm

With a little patience you can cut your own cylinder base and and crank case gaskets. I got the gasket material from Canadian Tire. You'll still have to meet the minimum order dollars when getting the head gaskets from Wildfire.
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