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personal preference or is there science behind it?

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i recently got my first two stroke dirt bike :bonk: i rebuild it bottom to top first time getting into a motor and it runs good still on the break in! anyways my question is regarding the replacing the piston and rings every so many hours. cant you just replace the rings instead of the whole thing dont they get most of the wear? but some people say 8 hours some say 20 some say 40. is it a personal preffrence or is there a way to tell when your getting close to a rebuild?

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i recently got my first two stroke dirt bike :bonk: i rebuild it bottom to top first time getting into a motor and it runs good still on the break in! anyways my question is regarding the replacing the piston and rings every so many hours. cant you just replace the rings instead of the whole thing dont they get most of the wear? but some people say 8 hours some say 20 some say 40. is it a personal preffrence or is there a way to tell when your getting close to a rebuild?

when your bike starts loosing compression or getting hard to start chances are its time for rebuild. there are service intervals in your service manual but not everyone follows them, if you run your bike right and not too lean and dont overheat alot, you can get away with a rering and deglazing the cylinder but if you run it lean or your over heating alot you can burn up a piston and hole it or melt it then you need to replace the piston and rings and most likely bore it out. basically if you treat your bike right it will last you, ive known of people going over 100 hours on a top end its all about how you treat your bike and how much abuse it receives.

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this bike i cant get many parts for so its going to be babyed and run 20:1 to be safe. i know how to tune an engine and stuff like that but my service manual says to replace every race. so i cant go by that.

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what kind of bike is it? if its a 125 its going to go through top ends more than a 250 just because you need to wring it out to get the power, i would go maybe 20-30 hours and spec it just watch for low compression, 2 strokes dont tend to blow up like a 4 stroke they just loose compression slowly and slowly till they just dont run anymore unless you have a leaking crank seal or are running lean

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its aa 1979 suzuki rm 125

yeah you should be set for about 20-30 hours, the old aircooled bikes dont over heat as easy, and they dont have radiators to boil over so you always have coolant if your moving. if it gets hard to start or starts loosing compression just grab a set of rings deglaze and crosshatch the cylinder and trow it all back together but if you blow it up your obviously going to need a complete rebuild

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If you're not going to ride it hard you can probly get 30-40 hours out of the rings just to be safe change the piston every other time you give it rings.

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The rings move up against the groove in the piston every time it changes direction.This causes wear that can be hard to detect.The new ring is then not held at the proper angle to the cylinder wall causing extra wear.I let my bike go longer between top ends and replace the piston and rings as a set.

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I replace just rings til my piston wears out.. It's a fact of life in a 2 stroke

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