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Before or after...

Discussion in 'XJ Technical Chat' started by PilotSmack, Jan 3, 2014.

  1. PilotSmack

    PilotSmack Active Member

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    Hey guys, a bit of an odd ball question, but since my ride is in a billion pieces in my basement and I'm about to order parts, I figured I'd ask. The dilemma is:

    Some of the valves are out of spec, but I wanna lap the valves over the winter. Should I just order what I need now, or lap em and then remeasure and order?

    Cheers!
     
  2. wizard

    wizard Active Member

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    You must lap first & be prepared to check them again once the parts are bedded in.
     
  3. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    How many miles on the bike that you feel the need to pull the head/lap the valves? Or is there something else afoot?

    Wiz is right; lapping the valves will change the clearances.
     
  4. 750E-II_29Rbloke

    750E-II_29Rbloke Active Member

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    What they said ^ :)

    Checking after lapping in is important since the amount of material taken off the valve head/seat, although tiny, will translate to a much bigger relative difference in valve clearance due to the working angle of the valve head & seat contact area, and the checking after bedding in is essential too as the parts may/likely will wear together slightly the same as they would on a new engine (the reason I believe the first valve clearance interval is shorter than normal on a new bike/engine)

    Fitz, I'm guessing from the o/p mentioning a "billion pieces" that the engine is already stripped & the lapping in is just one of those "better safe than sorry" items on the list, so it doesn't potentially have to come down for a valve job after it's built?
     
  5. PilotSmack

    PilotSmack Active Member

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    Right on the money bloke, the head is already off a couple of the valves really tightened up since the last time I checked, but one actually loosened, which is odd.

    Mainly it's all preventative maintenance. There's 40k on the bike, 8 of which I put on last year. The bike obviously sat around without love quite a bit, but someone definitely tried working on it as every other bolt on here isn't even metric. PO said he worked on it lots, but between the insane amount of gunk in the carbs, rusty chain, soldered connections and upside down footrests when I bought it, I frankly don't believe any of his work and would rather do it myself.
     
  6. PilotSmack

    PilotSmack Active Member

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    Oh, and thanks for the input guys! I figured that would be the right way to do it but figured I'd ask the pros!
     

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