Reply To: bottom cylinder fouling Big Twin 25hp

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November 16, 2020 at 11:19 am #220966
Don
Participant

    US Member
    Mumbles wrote:

    With parts #’s 91 and 92 missing, the top seal would be inoperative and this is likely where the oil is coming from. Since the oil can get out, that means air can also get in, causing a lean running cylinder.

    Maybe the bottom cylinder is burning properly, and the top one is running lean and leaving little deposits on the piston. It might be time to rethink this.

    Good point….