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Help Valve Clearance Inspection

Discussion in 'Kawasaki 250cc In-line 4's' started by DanoHosko, Mar 29, 2020.

  1. DanoHosko

    DanoHosko Member Premium Member

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    Hi all

    Using a guide for valve clearances, seems pretty handy
    https://themcdonalds.net/richard/wp/zx-6r-maintenance-adjust-valve-clearances/


    Couple things i need to clarify:

    The TDC marks for 1/4 and 2/3
    - at 1/4, either cylinder 1 OR 4 is at TDC, rotating a full turn to 1/4 again will put the other cylinder at TDC? Is that correct?
    - when at TDC, both pairs of inlet and exhaust valves can be measured (4 valves altogether)?


    I've been looking through the forums just cant seem to find this bit of detail.
    Praying i dont need to do the shims but not confident haha

    Cheers!
     
    Last edited: Mar 29, 2020
  2. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    1 full revolution on the flywheel from tdc on the compression stroke will bring number 1 cylinder to tdc on the exhaust stroke

    720 degree's at the crankshaft is 1 full cycle, 4 stroke's, Intake, Compression, Power, and Exhaust
     
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  3. DanoHosko

    DanoHosko Member Premium Member

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    Aha ok im confused now haha

    Do i measure both inlet and exhaust when the cylinder should be at TDC?
    When both cam lobes for that cylinder are pointing away from each other?
    < >
     
    Last edited: Mar 29, 2020
  4. pete05

    pete05 Member Premium Member

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    If your piston is at TDC then both valves will be closed so both inlet and exhaust can be checked.

    I just did mine and I required 11 new shims.
     
  5. DanoHosko

    DanoHosko Member Premium Member

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    Beauty thanks mate

    To be honest if it needs new shims am i just as well to do the cam chain as well?

    Chain has a couple tight spots, seems both when at TDC...
     
  6. DanoHosko

    DanoHosko Member Premium Member

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    [ATTAUmm, does this look right?
    Or does this say my timings out?

    I was under the impression the cam lobes should be exactly horizontal
    But to be fair the timing marks seem to line up nicely on the sprockets


    DSC_0215.JPG DSC_0216.JPG
    DSC_0217.JPG
     
    Last edited: Mar 29, 2020
  7. Andych

    Andych Well-Known Member Premium Member

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    OMG... please get rid of all that Silicone... and dont use any when putting the rocker cover back on... but a new gasket if you need to.
    If that stuff gets down into the sump it can very quickly kill an engine...
     
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  8. DanoHosko

    DanoHosko Member Premium Member

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    Yeah dont worry, ive been pulling my hair out with this silicone mess, previous owners sin though not mine!
    Should of seen the state of the carbs when i first took them off...
     

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  9. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    #1 cylinder is the left hand side, in your picture that is #4. Your crankshaft timing mark is in the correct spot.

    On top dead centre, the cam lobes will appear as in your picture. The important thing is to measure clearances when the cams are on the base circle, ie not the pointy bit. Camshaft timing will go 1-2-4-3. Start at your timing marks, then measure clearances in that order on each cylinder. When you've checked one, rotate the crank 180 degrees and check the next. So you will end up checking #1 first, #2, then #4 and finally #3. Do not rotate the engine backwards (anti clockwise)

    Cam chains and tensioners on the ZXR are a known weak point, the chains are tiny even compared to other 250 four's, and the tensioners are not a great design. Check the inside of the cam cover for damage where the chain runs, there is no plastic guide on the cover, though I have heard that some do have them, but can't confirm. None of mine had them.

    As for the shims themselves, measure them and see if they are 7.48mm, 7.55mm or 7.95mm, and check to see if they are loose in the valve spring retainer. Measure them as well to make sure you get the correct diameter shims.
     
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  10. DanoHosko

    DanoHosko Member Premium Member

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    Beauty!
    thanks for the help mate, I'll get measuring ;)

    Will inspect the tensioner too when I've checked the clearances

    Picture of cam cover, is a bit of scoring from the chain by the looks of it

    DSC_0219.JPG
     
  11. DanoHosko

    DanoHosko Member Premium Member

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    upload_2020-3-29_18-22-12.png

    Heres the valve clearances, looks like i got some work to do :headbang:
     
  12. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Those are all over the shop. Someone's been in there before and just changed the shims with the tightest clearance.

    The correct way to do the job is to change every shim to have each inlet and exhaust valve at the same measurement.

    This is useful because the bike will run smoother, and further down the line it can help reveal which valves if any are having problems, ie receding into the head or excessive clearance developing.
     
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  13. DanoHosko

    DanoHosko Member Premium Member

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    Ah ok, in that case i'll do it properly and replace them all to get them in the middle of the specifications i guess? Hopefully this will help sort out my poor idle issues too :p
     
  14. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Set them to the upper end of the specification. As valves and seats wear, clearance decreases. This is normal. Doing it that way gives you maximum time between shim changes. Do it once, do it right.
     
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  15. DanoHosko

    DanoHosko Member Premium Member

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    Ah copy that, thanks bud :D
     
  16. DanoHosko

    DanoHosko Member Premium Member

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    Cam tensioner when i removed it

    Not sure if its supposed to come apart like that, and no idea what the screw at the top does DSC_0221.JPG
     
  17. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    What @Linkin said. If you can't get them all the same it help to have the inlets on each cylinder the same. For example, both inlet valves on cylinder 1 have the same clearance. It has been my experience that you will get a smoother idle that way. Wouldn't hurt to apply the same strategy to the exhausts as well.
     
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  18. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    The small screw at the back holds the tensioner rod against spring pressure when you are fitting the tensioner housing back onto the engine. Loosen the screw, compress the rod against the spring and hold by tightening the screw. When back in engine undo screw a turn to release the rod onto the can chain tensioner, and retighten the screw.
     
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  19. DanoHosko

    DanoHosko Member Premium Member

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    Ah righto, I'll look into getting shims see what i can come up with
    I reckon the chain will need changing as its definitely got loose/tight spots

    Ah cheers bud, I'll chuck it back together today, might swap for a manual cct one day but not yet
     
  20. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    As Murdo said, the tensioner is meant to come apart like that. Following image for clarification. When you unwind the screw after installing the tensioner, you will here a metallic whack as the tensioner is released and the camchain should tighten.

    ZXR Tensioner.jpg

    I always wondered if having different inlet gaps helps with swirl? exhaust the same for sure. A bit like running inlet valves with a dome scooped out of them and flat faced exhaust valves.
     
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