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  1. #1

    Reason for PTO Piston to burn a hole in it?

    I bought a 99 Genesis 1200 (Carb). I have a dime size hole in the middle of piston. Cylinder walls seem good, just a honing I'm thinking. Question is what other then rear crank seal could cause this piston to burn out? I'm thinking (hoping)the bog problem was also part of the same problem does that make any sense?
    Last edited by PetroMan; 06-08-2015 at 07:26 PM.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    What maintenance has been done to the fuel system and especially the carburetors?

    If the carburetors have not been rebuilt in recent memory then that should be done.

    If the original gray Tempo fuel hoses are still in there then the entire fuel system should be gone through.

    The 1999 Genesis has an unusual exhaust system with dual under the hull exhaust exits. This exhaust configuration creates excessive exhaust back pressure at certain engine RPM and hull speeds.

    My understanding is that the problem is most severe from just off idle up until the hull is properly on plane. The mode to avoid is plowing the hull through the water with the bow high and the rear pressed down using engine thrust.

    The exhaust manifold was also revised in later model years to improve exhaust flow from the PTO cylinder.

    The stock 1999 exhaust manifold combined with the 1999-only under hull exhaust makes the engine sensitive to certain RPM ranges and hull speeds.

    I don't recall at the moment if there were any service bulletins regarding carburetor setting changes for the 1999 Genesis. There was a PTO cylinder head update for the fuel injected version of the 1999 Genesis.

  3. #3
    I replaced all fuel lines and diaphragms in carbs, I blew sea foam through all jets as well. But stopped short of total rebuild as have never done that before. Something else I just remembered is machine top speed was only 50mph on speedo
    Last edited by PetroMan; 08-06-2014 at 11:35 PM.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by PetroMan View Post
    I replaced all fuel lines and diaphragms in carbs, I blew sea foam through all jets as well. But stopped short of total rebuild as have never done that before. Something else I just remembered is machine top speed was only 50mph on speedo
    These engines really want the entire fuel system to be 100%

    I suggest rebuilding the carburetors using genuine OEM rebuild kits and ensuring the carbs are completely clean and properly adjusted. If you are uncomfortable doing the work yourself there are shops that do carburetor rebuilds.

    Other things in the fuel system that need attention are the fuel filter and the fuel selector valve. Both can be replaced with new.

    If you have a fuel/water separator then the o-ring seals need to be checked or preferably replaced.

    Sometimes the fuel tank venting check valves can stick open or closed. There are two for the fuel tank and a separate one for the oil tank.

  5. #5
    Ok thx K447, I will need to learn so I will be diving into the fuel system.

  6. #6
    LaveyT's Avatar
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    A leak down test would be a good idea as well. You may have an air leak. Before I would run it again I would Do as Keith suggested and while the carbs are off do the leak down test.

  7. #7
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    Salt water or fresh water? If the engine has the original rear crank seal, salt warer was known to corrode the case around the seal and cause a leak. The double rear seal fixes this issue.

  8. #8
    Fresh water, and yes a leak down test would be a good idea. I will be doing that for sure.

  9. #9
    StevoH@O's Avatar
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    I too purchased (2) 99 Polaris Genesis over Memorial Day. I had an issue where the unit with 200 hrs would start and idle fine and would shoot up to 30 MPH and higher - but nothing in between... (5-30 mph did not exist). I rebuilt all 3 carbs and replaced all fuel lines and the condition improved - based on strong suggestions on this site (thank you all!) It still wallows during acceleration and I have to pump the throttle sometimes, but I can settle into a low 20's cruising speed that I could not find before. Hope this report helps you with your future plans. Also the CDK II don't have any high speed screws that I have ever seen which only leaves the low speed adjustment. I just left that setting alone during and after the rebuild. DK if that is sound, but it was the easiest thing to do....
    Stevo

  10. #10
    Sounds very similar to what this machine did, sometimes I could pin it from idle and it would get up and go but most the time I had to feather it to keep it running. After I did fuel line change and blew sea foam through carbs it did improve some. Before that it would die if at cruising speed I simply let go of throttle, but after I blew seafoam through carbs it dropped to idle and stayed running.

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