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  1. #1
    BLACK MAGIC HEADERS hydrojunkie's Avatar
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    Help me understand why to drill the rocker shaft

    As per folk on this site, if you plan to run a valve train setup on a 06 and newer engine you are suppose to drill the rocker shaft to 3mm. Now in theory if you drill it larger you will increase volume and decrease preasure therefore your lifters will not pump up all the way.

    As per les cooke he does not do any of that and his engines run upto 10,000 rpm when the ski comes out of the water and has no problems. I just cant comrehend that. Who said it "must be done" why.


    Is rotax oil jet for the 04 05 engine larger or smaller.


    On my turbo ski the valve seat spun on all intake valves and i wonder if that had something to do with it.


  2. #2
    Duke's Avatar
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    Quote Originally Posted by hydrojunkie View Post
    As per folk on this site, if you plan to run a valve train setup on a 06 and newer engine you are suppose to drill the rocker shaft to 3mm. Now in theory if you drill it larger you will increase volume and decrease preasure therefore your lifters will not pump up all the way.

    As per les cooke he does not do any of that and his engines run upto 10,000 rpm when the ski comes out of the water and has no problems. I just cant comrehend that. Who said it "must be done" why.


    Is rotax oil jet for the 04 05 engine larger or smaller.


    On my turbo ski the valve seat spun on all intake valves and i wonder if that had something to do with it.

    I seriously doubt the seat spinning has anything to do with to much or to less of oil getting to the rockers. Most likely this is caused by the rapid heat cycles of the open loop setup. Even when still in the water, when engine is shut off all the water drains out of the motor causing a quick heat cycle. The head retains most of that heat and in a closed loop enviornment will have heat removed from the coolant under pressure.

  3. #3
    speedskixp's Avatar
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    Quote Originally Posted by Duke View Post
    I seriously doubt the seat spinning has anything to do with to much or to less of oil getting to the rockers. Most likely this is caused by the rapid heat cycles of the open loop setup. Even when still in the water, when engine is shut off all the water drains out of the motor causing a quick heat cycle. The head retains most of that heat and in a closed loop enviornment will have heat removed from the coolant under pressure.
    Good point.

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    Duke's Avatar
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    I'm interested in all the theories on the oil hole size etc.too. Does the valve train really need extra oil in above 8500 rpm on the 06 and up motors?? Why not just put the 04-05 rockershaft in there???

  5. #5
    BLACK MAGIC HEADERS hydrojunkie's Avatar
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    It just doesnt make sense on this dumb oil jst stuff. If you run more rpm you should build more oil preasure unless there is a relief in the oil system to not exceed over "x" psi.

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    speedskixp's Avatar
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    Quote Originally Posted by hydrojunkie View Post
    If you run more rpm you should build more oil preasure unless there is a relief in the oil system to not exceed over "x" psi.
    I'm not sure but is that not what the little piston valve thingy does?
    #13 on this page. http://partsfinder.onlinemicrofiche....=13&A=139&B=12

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    I think you could be right. It is like the BOV. Someone said install it and your SC will last longer yet there is no proof this is true. Goes back to the older motors and installing the larger oil jet. There is no harm in doing that to theoretically supply more oil to the head. Well BRP redesigned the system and everyone was like "how do we increase oil flow now?". The restriction was the rocker hole so someone decided it would be OK to just enlarge the hole.

  8. #8
    BLACK MAGIC HEADERS hydrojunkie's Avatar
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    Quote Originally Posted by ncheel View Post
    i think you could be right. It is like the bov. Someone said install it and your sc will last longer yet there is no proof this is true. Goes back to the older motors and installing the larger oil jet. There is no harm in doing that to theoretically supply more oil to the head. Well brp redesigned the system and everyone was like "how do we increase oil flow now?". The restriction was the rocker hole so someone decided it would be ok to just enlarge the hole.

    it's larger in the 04 05 engine ,the block has the oil jet.


    The 06 and up there is no jet and the rocker has a small oil input smaller the 04 05

  9. #9
    EZ Dock of Long Island Shibby1485's Avatar
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    Quote Originally Posted by Duke View Post
    I seriously doubt the seat spinning has anything to do with to much or to less of oil getting to the rockers. Most likely this is caused by the rapid heat cycles of the open loop setup. Even when still in the water, when engine is shut off all the water drains out of the motor causing a quick heat cycle. The head retains most of that heat and in a closed loop enviornment will have heat removed from the coolant under pressure.
    i kind of had the same thought when speaking to jason... couldn't really connect oil pressure to valve seats in my mind

    but yea... bottom of the PTo cover one of those plugs is a spring with a pressure regulator that goes into the pressure pump in the PTO

  10. #10
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    Quote Originally Posted by hydrojunkie View Post
    it's larger in the 04 05 engine ,the block has the oil jet.


    The 06 and up there is no jet and the rocker has a small oil input smaller the 04 05
    I understand that. Changing the oil jet basically affects nothing. Drilling a larger hole in the rocker affects a moving part. I have only dealt with the '04-'05 engines as that is what I have. I thought you were questioning the hole itself. If you are questioning the amount of oil the larger hole allows to pass then I have to say no. The increased oil is not going to cause your problem.

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