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Piston to valve clearance and milling the head

Discussion in 'XJ Technical Chat' started by Kickaha, Jun 28, 2009.

  1. Kickaha

    Kickaha Active Member Premium Member

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    Does anybody know the piston to valve clearance on a stock 550 Seca or how much you can safely surface grind the head to bump up the compression?
     
    Kickaha, Jun 28, 2009
    #1
  2. Thijs_205_Rallye

    Thijs_205_Rallye Member

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    Why mill the head in the first place? A safe way of determining the clearance is applying some clay/playdoh on top of the piston and turning the engine by hand. You will have to open up the engine off course to do so ;).


    grz Thijs
     
    Thijs_205_Rallye, Jun 28, 2009
    #2
  3. MN-Maxims

    MN-Maxims St. Paul Minnesota

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    When
    i had my 750 head off for a valve job It was milled off .020 with no valve to piston problems.

    MN
     
    MN-Maxims, Jun 28, 2009
    #3
  4. Kickaha

    Kickaha Active Member Premium Member

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    To increase the compression , the bike will be running avgas and being used as a post classic race bike, this is only the first step in a series of modifications
     
    Kickaha, Jun 28, 2009
    #4
  5. Thijs_205_Rallye

    Thijs_205_Rallye Member

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    Allright, then I would definately go for the playdoh method ;). You can recycle the old headgasket and base gasket for measurements.

    Also planning to mill/turn the base circle of the camshaft to increase valve lift? Then I would suggest doing that before milling the head and measuring ;).

    Always nice to see such a old skool project. Keep us posted!


    grz Thijs
     
    Thijs_205_Rallye, Jun 29, 2009
    #5
  6. Kickaha

    Kickaha Active Member Premium Member

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    When I can find one I am planing on fitting a 600 head as supposedly they have bigger valves and a cam with more lift and duration, I need to get a hold of one to check if this is correct

    The engine will also be overbored to 59.5 using 1mm oversize 600 pistons

    The engine I'm using at the moment is just a "fill in" while we work on one of my spare motors but has a head gasket leak so it has to come off anyway
     
    Kickaha, Jun 29, 2009
    #6

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