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bob asked in Cars & TransportationMotorcycles · 2 months ago

New 2 stroke?

I am getting 2 stoke, a yz85 and I was wondering if there is any maintenance tips for owning this bike since it is my first 2 stroke. I am 5’11 135 pounds so hopefully its a good size. I am experienced with riding 4 strokes but obviously fuel mixing is different. Any tips are greatly appreciated!

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  • 2 months ago

    A booklet comes with it that will tell all you need to know, except carry a fresh sparkplug with you all the time. Lookit: pp3-3: https://www.yamahamotorsports.com/assets/service/m...

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  • Manufacturers of 2 stroke engines typically specify a fuel to oil ratio that is a compromise of decent engine life vs spark plug life and lower emissions.  Since new pistons cost more than spark plugs, I run mine with a bit more oil than suggested.  Counter-intuitively, rings stick less and pistons run cleaner with more oil, but you have to go up a jet size or two to compensate for the engine getting less gas through the jets and change a plug slightly more often.

    2 stokes are also more sensitive to ring leakage, so break-in is very important.  Limiting load and rpm (and thus piston temperature) for the first 15-20 hours will not only allow mating surfaces to become acquainted with each other, but it will also allow the stresses within the piston created during its manufacture to dissipate so that it will not warp and permanently prevent proper ring sealing.

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    • Ah, yes, race motor!  They still need break-in, too bad a proper one is a luxury for them.  Repeated hot/cold cycles will alleviate piston stresses faster, and they still like more oil.

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