Inlet valve recession

Discussion in 'Motorbike Technical Discussion' started by Mark P, Jan 2, 2004.

  1. Mark P

    Mark P Guest

    Hi all,

    I have an FZR1000 EXUP and I'm in the process on an engine rebuild.
    I have noticed bad inlet valve recession on all 3 inlets on cylinder 1.
    All other valves are fine. I have a Scottoiler attached to cyclinder 1.
    All spark plug colors were pretty much the same - darkish brown - certainly
    not white.

    There are a kind of ring markings in the seat and valve - perhaps there
    was some valve rotation. The valves were holding parafin (kerosene) as well
    as any of the others - very very slight leackage from most of the valves!

    Has anyone noticed this kind of recession on inlet valves before.
    And what could cause it? Why all inlets in one cylinder?
    I don't believe the Scottoiler
    was leaking vacuum!

    Any help appreciated!

    Mark
     
    Mark P, Jan 2, 2004
    #1

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  2. Mark P

    Mark Olson Guest

    The ScottOiler uses engine vacuum to open a valve that allows oil to
    flow to the chain. When the engine stops, the flow of oil shuts off.
     
    Mark Olson, Jan 2, 2004
    #2

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  3. Mark P

    Mark P Guest

    Dave,

    The Scottoiler is a chain oiler but it is 'switched on' by the
    presence of engine vaccum - so a line is taken from a a carb sync
    point to it.

    The bike has done 30k miles - it does a lot of town miles - short
    jouneys - and I first rebuilt it about 2 years (8000 miles ago)
    to do a decoke - and there was a hell of a lot of carbon on the
    valves and head. I put it back
    together without honing and re-ringing and it then started
    burning a lot of oil - a pint every 200 miles. So this rebuild
    is to get it honed and re-ringed. The pistons and barrels are
    within spec and everything generally looks good apart from
    the three inlet valves and seats on cylinder 1! And there is
    again quite a build up of carbon on all cylinders.

    Cheers,
    Mark
     
    Mark P, Jan 2, 2004
    #3
  4. Mark P

    Steve H Guest

    FZR1000Exup engines have a reputation for inlet valve seat recession, which
    appears to be deserved. I checked the valve clearances on mine at 20,000
    miles and ALL the inlets were tight and needed reshimming. I think its just
    a case of checking more frequently than the recommended 26,000 mile
    intervals but even so I don't think the valve seat recession is rapid enough
    to cause any major reduction in engine life, they just need adjusting more
    than Yamaha were prepared to let on!

    Steve H
     
    Steve H, Jan 2, 2004
    #4

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