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77 YZ80D Fuel Fouling Plug

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  • 77 YZ80D Fuel Fouling Plug

    Working on a cool old 77 YZ80D for my daughter- sat for a few years as I understand it. Got it running right away, ran good for a while, but then started dying. Took the fuel tank off and completely cleaned it out, as well as the fuel valve. Installed new fuel filter and hoses. Then, took carb all apart, very carefully and completely. Completely cleaned out all orifices and replaced all that I could-- all gaskets, being careful not to change or damage float, needle/seat, etc. Cleaned and blew out jet, everything. Put back together. Now, it will run great for just a few minutes, then will begin to run rough and die. When checking the plug, it looks fuel-fouled. Clean up the plug, and it then starts all over-- runs great for a few minutes, then begins to run rough and dies. Plug out-- it looks very wet. Would an incorrect (not hot enough) plug cause this? It has a main jet size of 170, which if memory serves when sourcing parts the offerings were 160 and 180. Any ideas? When it's running normally for those few minutes, it runs great. Oil mixture I think I have right, but just in case, too much oil-- would that cause this? thx-

  • #2
    Didn't that one have an oil injection pump under the RH front cover?
    And electronic ignition under the LF cover?

    Might need to find a manual to make some tune-up adjustments.
    Richard

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