749 Valve Adjustment Question ('06 749)

Discussion in '749 / 999' started by vbroom, Jun 19, 2020.

  1. Hey guys.

    In the middle of my first valve adjustment. All my valves are in spec except for the horizontal exhaust - both closers and openers. Closers are very loose. (around 0.3mm) Openers are very tight. <.05mm)

    I thought to order half rings first and see what difference that made.

    Installed the new half rings tonight. replaced the cam (without the bridges) to measure the closer and the gap on the right valve has grown larger?? from initial 0.3mm measurement it is not 0.58!. I'm confused how this could happen....

    I did give the rocker a few good flicks to seat the half rings. Is it possible this does any damage to the valve seats at all? I have no other explanation for how the clearance could get larger....

    I'm gonna try reinstall the old half rings tomorrow and see if i get the same measurement as before...

    edit: Reinstalled the old half rings...got the same huge measurement...scratching my head now
     
    #1 vbroom, Jun 19, 2020
    Last edited: Jun 21, 2020
  2. My theory is that it is unlikely the valve seats have been damaged. More likely that the old half rings have been crushed slightly in operation thus closing the gap. Fitting the new un crushed half rings have the effect of settling the shim lower down the valve shaft hence opening up the gap again.

    TB
     
  3. If i'm not mistaken, when the shim is moved down from the newer uncrushed half rings, the gap will infact CLOSE up. which is what i was trying to achieve however, now the gap is larger...and almost double at that....
     
  4. Yes you are correct, I was thinking of the opener. . Apologies for my mistake.

    TB
     
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  5. Have you got an picture of the half rings that came out of your 06 749?
     
  6. IMG_20200622_112959.jpg
     
  7. So i think i figured out why the gap was increasing. I was measuring the closer clearance, without the cam shaft support (bridges - whatever you want to call them) in place... As far as i understand....having those supports in shouldn't affect the closer clearance...only the openers...

    BUT. the shims were so out of clearance, when i put the support back on, the opener has zero clearance...and when the supports are tightened down, the cam is then appyling pressure the the opener shim...even at rest...which then brings the closer back to my original measured clearance.

    so my next (dumb) questions is....when the cams are on and tightened down with the supports....at rest position, there should be NO pressure at all on the openers right?

    Hence.....if I leave the opening shim off for now, and put the cam back with the supports bolted back down...I should be able to get a more correct reading for my closer?
     
  8. To me this makes sense now...(having a exhaust valve that is slightly open in rest position) because my bike had been running very poorly...idle was really bad..constant cut out. And also the exhaust header from this cylinder was VERY hot. Almost to the point if i was still at the lights for more than a few minutes, my inner thigh was getting borderline burnt.
     
  9. Have you got an workshop manual?

    clear.jpg
     
  10. Yeah i have one. I have looked at that page many times :)
     
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