Engine Trouble Investigate oil leak on 80cc Umoto motor

Discussion in '2-Stroke Engines' started by David H, Aug 15, 2016.

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  1. David H

    David H Guest

    Hello all,

    I have a problem and just need some guidance getting pointed in the right direction to resolve it.

    I have the 80cc Ignite from UMoto, and it's been pretty good so far for getting around. Recently I ran into a problem where it seemed the clutch was no longer engaging. I pulled the clutch cover and found gas/oil was smeared all over the inside, preventing the clutch pads from locking to the clutch plate. After doing some research, because I can't seem to find a good exploded diagram of the whole assembly, I figured out how to pop out the clutch plate and the part that holds the clutch pads. A little time, a little degreaser, and washing the clutch pads with Dawn detergent, and some drying, reassembled and voila, bike started.

    I had suspected that because this clutch plate had no gasket that oil/fuel had leaked from the fuel bowl on the carb down into the clutch assembly over time. Got some gaskets and really good gasket sealer, sealed it up and off we go.

    Well, it looks like it happened again so it's definitnely not from a fuel leak from the carb. The oil in there looks like it's been 'burned' if you will. I have also noticed that oil rarely, if ever, comes out of the exhaust pipe.

    Barring a crack in the crankcase, what I'm trying to determine is where oil could be leaking in 'from'. See, I don't really understand the assembly down there. For example, I'm not sure which of the two "gears" that make up the clutch are connected to the axle which is essentially the crankshaft. I am guessing, and I admit I don't "know", that oil accumulates in the bottom part of the engine. Beats me where it goes from there. There's just stuff about two cycle engines I haven't learned yet.

    I'll be testing later where I"ll clean everything up, keep the clutch cover off, start the bike and just 'watch'.

    I guess what I'm asking is do either of the two axles rotated by the gears in the clutch pass through an area where oil accumulates?

    I don't suppose anyone has a good high-res exploded diagram of this area?

    Thanks in advance for your consult.

  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    The oil is coming from a leaking seal on the crankshaft under the 20 tooth bevel gear.

    Pull the gear to replace the seal by pushing a new one in. You need a special puller.
    Also Check the seal on the left side under the magneto cover.

    A blown seal can make your motor run lean by sucking air which can melt a hole in your
    piston from the heat.