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Thread: You tell me...

  1. #1
    olds72's Avatar
    Join Date
    Nov 2009
    Toledo, OH

    You tell me...

    OK, you all know I was having problems with my plugs fouling after about an hour of riding. Two weeks ago It did the same thing and I made some adjustments to the oil pump, It set way to rich. I cut back my spark plug wires. Then my ski wouldn't start. So I check the spark and it was good. I was getting fuel. So the next step was to check compression. I did that today. What I found was the mag side at 130 lbs and the pto at 20 lbs. I pulled the head and this is what I found. This motor has only 4 hrs on the rebuild. What went wrong?
    Pic 1 is the PTO piston notice the top had indents or nicks. Pic 2 is the mag side cylinder wall, it has score marks(odd). Pic 3 is the pto side cylinder head. It also has little nicks., but is not black from carbon. Pic 4 is the mag side of the cylinder head. It has one indent in it, but otherwise it's just black. What do you recommend?

  2. #2
    Left Pic is serious Detonation causing the Piston Rings to overheat and shatter embedding shards of
    iron ring in the Aluminum Head Dome and top of Piston.

    Right Pic is a collision with of some steel object (small washer or Spark Plug electrode ?) that bounced around in between the Piston Top and Squish Band ledge before getting blown out the Exhaust Port.

    That "black" Piston top is not Carbon, it's burnt Aluminum--
    That Piston (and probably the Rod) got really really Hot.

    Either way, that engine will need to be rebuilt. Top End job at a minimum but
    usually the lower end (Crank Bearings and Inner Crank Seals) get their share of metal debris
    which will seize a newly rebuilt Top End unless it's all cleaned out.

    Tough break---- You need to find out the root cause of all this.

    Was any Oil added to the Fuel Tank ? Pre-Mix ? Clogged Oil Filter ?
    Clogged Injector ? RFI Compression should be approx. 150~155ish---

    Who bored the Cylinders on the rebuild ? What Sleeve/Piston clearance
    was the final honing done ?

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