Can I reuse rings?

ignition retard said:

I've done this alot. No break in required. I've also found that pistons and cylinders wear alot faster than rings, needle bearings and wristpins. If you took the piston off the conrod, then it's advisable to replace whichever circlip you removed with a new one. In a pinch I've even reused circlips by bending them back to their original shape, but this isn't the smartest thing to do. I've reused base gaskets and head o-rings with 100% success also.

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Note to self. Never buy a bike from this guy. :whoa:

Never reuse rings. They may not look worn but if they have been run for any length of time, they are worn. Your piston rings are what seals your compression. Once they are disturbed, they lose that seal. The sharp edges of the ring wear when the piston rocks in the bore. You may not be able to see the wear with the naked eye but it is there. When that sharp edge is gone, so is your compression.

Like Pred said. The rings are the cheap part of a rebuild. Why in the world would you not replace them?

ignition retard said:

Here's the point I was trying to make. Rings are reused every time you start the engine.

Now this is something I'm not really sure about. I've always thought that the old ring would seal better with the bore that it was "worn into", .

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It is very difficult to see the wear on your rings with the naked eye. When a ring is new, it starts out with sharp edges and a flat sealing surface. As the piston reaches tdc and bdc and changes position, it rocks a little bit. The rings also rock in the ring lands. When the bore and the piston wear, they rock even more. As the rings rock they wear the sharp edges down and eventually round off the flat surface of the ring. When this happens, compression can escape past the rings.

When a ring 'seats in' to the bore it produces little irregularities where dirt and grit get past the air filter and gets into the cylinder. These form microscopic scratches in the cylinder and corresponding scratches on the ring surface that match each other. When you remove a worn ring and reinstall the same ring, these microscopic irregularities don't line up any more. Now, you not only have worn edges and a rounded sealing surface but you also have many of these scratches and irregular areas letting your compression pass by the rings.

This is why the rings should be replaced every time the cylinder is removed even if the rings are fairly new. The cylinder should also be lightly honed to remove those small irregularities and insure the new rings have a smooth surface to seat against. (This is just my opinion and some piston manufactures suggest not honing the cylinder.)

The next time you remove your rings, inspect them through a magnifying glass or even better, a microscope. Then compare the used ring with a new ring. I guarantee you won't want to put the old ring back in your engine.

Loss of compression is one of the biggest factors in a poor running engine.