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extra tight valve after fairly recent re-shim, what's going on?

Discussion in 'XJ Technical Chat' started by seca550RK, Apr 18, 2015.

  1. seca550RK

    seca550RK Member

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    bike: xj550rk 13,000 miles

    I decided to re-check the valve clearance before tuning the carbs. I just re-shimmed the valves last year maybe 1500 miles ago. Two clearances were out of spec and rechecking my numbers from last time I found that both of these valves had zero clearance last time. One exhaust is at .07mm and one intake is still zero after exchanging a 265 shim for a 255. What's going on? I'm seeing a rebuild coming...

    There is also some slight burning marks on the valve cover. I don't know if this is normal or not.

    I did a compression check last time around and had good numbers. slightly on the higher side.

    This is a daily driver so I need to figure it out asap!

    Thanks, Mike
     
  2. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    When you did the valve clearance checks before how did you determine which shims to use?
    Did you use a very thin shim in the buckets that had zero clearance, or did you just guess?

    The marks on the valve cover are probably just baked on oil from a weepy gasket.
     
  3. seca550RK

    seca550RK Member

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    I think I guessed at the size and then rechecked the clearance. I know it was in spec when I finished.
    That's good to know about the marks, I thought it might be sign of something worse.
    From what I understand, it seems like either the shim isn't seating properly, (maybe oil underneath??) or I have some very rapid
    wear of the valve seats or valve.
     
  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    If the shim is not sitting flush with the bucket then you will get a flase measurement. but that typicaly only happens when putting a new shim in. The cam will push the shim into place, even though there is oil under the shim.

    This time order a 240 shim to do your clearance check on the zero clearance valve, then order the shims that you need to get them in spec. NO GUESSING ALLOWED.

    You may have rapid valve seat wear, or cam nose wear (unlikely), or have gotten soft shims (rare, but it does happen). Keep running it and do another valve clearance check before drawing any conclusions. I'd check again in 500 miles. If they are good then go out to 1500 miles, and finally again at the normal 5,000 mile interval.
     
  5. seca550RK

    seca550RK Member

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    Alright thanks, I'll do that. I've got a 255 with zero clearance so the 240 might even be in spec.
    The shim being so small is part of the worry. It was a 280 that I changed out the first time.
    I still don't see the problem with guessing as long as you check and correct it if it's wrong.

    I'm hoping it's not as bad as I think. I'll see if my local shop has the shims tomorrow (surprisingly he had some last time) and I'll get back with any updates.
     
  6. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Guessing is fine if you have extra shims to do your guessing with. Otherwise you're just going to spend more money for no good reason.
     
  7. seca550RK

    seca550RK Member

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    Yeah I held onto my extras from last time. Thinking ahead for once...
     
  8. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Did you do your clearance measurements with the bike overnight cold, or had you run it first?
     
  9. seca550RK

    seca550RK Member

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    it was overnight cold and about 60 degrees out.
    The last time I checked the clearance it may have been in the 40's but I can't imagine it would change it much.
     
  10. seca550RK

    seca550RK Member

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    hogfiddles, is the shim pool still going? I don't know if there would be any 240's or 245's anyways but thought I'd check.
     
  11. mikeames

    mikeames Member

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    Seems like the book says to rotate the engine several revolutions (by hand) after changing a shim (I assuming this is to help the shims seat all the way into the buckes). I'm thinking it was ten revolutions....
     
  12. seca550RK

    seca550RK Member

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    Yeah that was actually part of the problem. They still needed to go down 2 -3 shim sizes which I thought was still a lot.
    I didn't keep good records last time, so these might have been right on the cusp. I also noticed that if you're not careful lining the lope up 90 degrees from the
    bucket you can get bad measurement. It's just so damn hard to tell except for the right side valves were you have the slight cutaway. I used these to get a reference position to the brackets to help line up the rest
     
  13. Polock

    Polock Well-Known Member

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    records, if you wipe the tops of the cam bearings off real good with brake cleaner and write the shim size on it with a sharpie, it will still be there next time you check them.
    i thought it would come off but it didn't
     
  14. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Well....if you're lined up 90 degrees, you're gonna keep getting bad measurements. Your lobe should be 180 degrees from the shim to take your measurement.

    dave f
     
  15. seca550RK

    seca550RK Member

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    Haha yeah that's what I meant. I've got them pointing directly away from the shim.
    Polock - that does seem surprising but at least you won't lose your records. Seems like I've got bigger problems though.

    Still have a problem...
    I rechecked the valves again after ~600 miles and the intake #1 is too tight to get a 3 mm feeler gauge under. I haven't swapped in a smaller shim
    to get a real measurement, I'll do that next. Anyone have an idea what's going on here?
     
  16. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    3mm? That's like 1/8". Hopefully that's a typo........... !!
     
  17. seca550RK

    seca550RK Member

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    That is a typo, I forget where the decimal place is but it think .03.
    Anyone have any ideas?? I'm wondering what the next step should be and what I might need before removing the cylinder head.
     
  18. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Is that .03" or .03mm?
     
  19. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    As was mentioned before, swap in a 240 and do a clearance check. IF the valve is still tight with a 240 then you will need to decide between having new seats put in (have the valves fully serviced too since they have to come out), or get a used head.
     
  20. seca550RK

    seca550RK Member

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    .03mm

    Alright, I'll go swap that out in a minute and give an update. Are you assuming the seat is worn to far based on the shim size?
    I'm a newb to this kind of engine work, but I'd like to do as much as a can if possible.
     

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