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Pinned FZR250, ZEAL, FZX250 Valve Clearances howto

Discussion in 'Yamaha 250cc In-Line 4's' started by ruckusman, Nov 1, 2013.

  1. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK guys
    This is a simple step by step howto for doing the valve clearances.

    Tools I assume you have already: Good quality set sockets, with a screwdriver handle for 1/4" drive sockets as this gives more feel than with a ratchet bar. You'll likely also need a 3/8" drive -> 1/4" socket adapter for the 8mm bolts on the cam retainer shells.

    Good quality set of allen keys or socket equivalents.

    Tools you'll need past what you may already have in your possession:
    Decent quality set of feeler gauges - cheap ones I had were approximately 0.02-0.03mm too thick over the 0.1mm range.

    Good quality torque wrench which goes down as low as 7.2 ft/lb - You can get them even at Bunnings 3/8" drive Kinchrome ~$80. I consider this compulsory.

    Some molybdenum disulphide grease - I've already got some LMM CV joint grease on hand.

    I removed the engine, to clean it and the surrounding frame areas.
    I'm going to assume you're up to already having removed the rocker cover and the stator cover.

    TDC = Top dead centre
    BDC - bottom dead centre
    Both these terms are usually used in relation to cylinder one - TDC used alone is usually a reference to Cylinder one firing.

    Note: the firing sequence is #1 -> #2 -> #4 -> #3
    Cylinders are 1-4 left to right , sitting on the bike

    First step is to measure the actual clearances.

    I marked the stator with a thick black sharpie to make it easy to see the 0 and 180 degree points.

    IMG_20131031_150956.jpg

    I also marked the inside of the stator with the cylinders which are at top dead centre for each 180 degree rotation on the inside.

    You can make out the rotation direction arrow and the TDC - zero marking on the stator and the small zero extrusion on the case.

    Set the crank to TDC - I had removed the plugs and did all of the rotation by hand so I would feel any resistance later when I'd re-assembled everything.

    Check the two dots on the cam retainers/shells against the two small holes in the ends of the cams. If you don't see the dots then you are at TDC - cylinder #4 firing.
    I'll add a close-up photo of this later as I forgot to take it.


    Note: I've made two versions of the table to keep notes on the clearances depending on which orientation you're working and if the engine is still in the bike.
    Valve-Clearance-Reverse.pdf is for working with the engine facing you i.e working from the exhaust side
    Valve-Clearance.pdf is for working from the intake side.


    Next check your clearances for cylinder #1, work from the lower clearance up.
    Intake valves cylinder #1:
    0.1mm straight single feeler gauge ->
    0.05mm + 0.08mm ->
    0.1mm + 0.05mm ->
    0.1mm + 0.08mm ->
    0.2mm - upper limit

    If you're below minimum, hopefully not, work backwards till you can get a reading.

    Exhaust valves cylinder #1:
    0.2mm straight single feeler gauge ->
    0.15mm + 0.08mm ->
    0.15mm + 0.1mm ->
    0.2mm + 0.08mm ->
    0.2mm + 0.1mm - upper limit

    Now the reason I combined smaller feeler gauges where possible is because the those two will bend easier down into the space past the rocker cover gasket edge on the head.

    Note the clearance ranges lower limit reading<X<upper limit reading for intake and exhaust on cylinder #1.

    Rotate the stator 180 degrees so that Cylinder #2 is firing.

    Take measurements and note your readings.

    Rotate the stator 180 degrees so that Cylinder #4 is firing. This is TDC - ZERO marking on the stator.

    Take measurements and note your readings.

    Rotate the Stator a final 180 degrees so that Cylinder #3 is firing.

    Take measurements and note your readings.
     

    Attached Files:

  2. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    The next step is to simply remove the cams to get access to the buckets and shims above the valves.

    Before removing the cam retainer bolts the engine should go back to TDC #1 cylinder firing with the alignment marks on cams and retainer ends visible and aligned

    Please note that I haven't removed the cam chain tensioner at this stage - that comes later. The chain tension also keeps the cams down because there is one pair of valves on each cam partially depressed which makes the cam want to rise out of the lower retainers.

    Start by loosening the retainer cap bolts a quarter turn at a time - there isn't a loosening sequence that I could locate.

    Then go through and give them a half turn each and finally a full turn.

    Once loosened fully - I left the bolts in position

    Now if you remove the cam chain retainer and bolts separately there will be one vacant bolt hole so there will be no confusion as to which retainer goes where.

    IMG_20131031_151824.jpg
    There's also small black ticks and crosses, for valve clearances that were in the middle of the range - ticks and for valves that were in the low end of the range - crosses.

    Fortunately mine were all within spec, with 4 intake valves though they were between 0.1mm and 0.13mm so they got the largest clearance increase.

    The retainers have an arrow pointing towards the right of the engine - as viewed sitting on the bike.
    I also marked them with IN and EX and placed them in position on the bench with the cams once removed.

    You may have to wiggle them to get them up off of of the dowels - patience and subtlety are key here, if they start to come off crooked tap the high side back down.

    Please note also that the each cam has an I marked on the intake cam and and E cast on the exhaust cam, between some lobes so there should be no confusion as to what goes where come time to re-assemble.
     
  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK so now to removing the cams
    It's time to release/remove the cam chain tensioner on the intake side of the cylinders.

    12mm socket, undo and there's two concentric springs so once fully loosened the bolt will want to escape. Mine also has a copper sealing washer.

    Once that's done, remove the cam chain tensioner

    cct components.jpg
     
  4. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    My gasket tore when I removed it so I made another out of 0.4mm gasket paper. - That's for later.

    To ease the tension on the chain rotate the stator backwards a little - then you can remove the exhaust side chain tensioner which goes down into the engine.

    IMG_20131031_154817.jpg

    Also remove the retainer dowels in the centre of the engine - these pics are at the re-assembly stage - thus the moly grease but you get the idea. Some will come up with the retainers and some will remain in the cylinder head.

    IMG_20131031_150823.jpg

    The above shot is with the intake cam removed, so I advanced the timing on the stator a small amount to give some free chain travel so I could lift it.

    Do the same for the exhaust cam, retard the stator timing slightly to give the cam some freedom to rotate up and out of the lower shells.

    I placed a compression tester extension in place below the chain to keep it from falling into the crank cavity.

    Pic of chain prevented from falling down into the engine.

    IMG_20131031_145740.jpg
     
  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK next step is to remove each bucket and shim to record the thickness of the shim. I did these one at a time, i.e removed one, then replaced it before proceeding to the next one. Each bucket should go back to it's original position as it will have mated with bore in the cylinder head, so just pulling them all at once isn't sensible unless you have the space to lay them all out carefully in order for re-assembly.

    I used a magnetic pickup tool to do it and the shims came out attached to the underside of the buckets.

    IMG_20131029_180259.jpg

    At this stage you may need some vernier calipers of a 0-25mm micrometer. If the shim thickness etching was placed face down onto the top of the valve it may be worn and illegible. I had two that were illegible or at least difficult to be certain of till I had used the micrometer on them.

    Now when it comes time to calculate the required clearance changes just use the worksheet in a vertical flowing downwards direction.
    Presumably you're going to need to keep the same clearance or increase it.
    Any increase in clearance is going to require a thinner shim. So for the four intake valves which were at the bottom end of range:
    0.1mm < clearance < 0.13mm I deducted 0.07mm from the shim value. E.G 182 became 175 yielding the 0.07mm clearance increase I required.

    www.precisionshims.com.au is the place to get them - I ordered one day and had them the next morning with the postal delivery.

    Their thicknesses ranges go 00 - 02 - 04 - 05 - 06 - 08 - 00
    You want 7.5mm diameter ones - the smallest ones they offer.

    You can use the next closest i.e up or down 0.01mm -> 0.02mm as it's the thickness of a piece of cigarette paper

    For all of my exhaust cams I increased by between 0.02mm > 0.04mm to put them into the upper range and the intakes by between 0.04mm . 0.07mm.

    I noted on the worksheet, which ones I had from thinnest to thickest, and which ones I needed then simple process of elimination to see what I needed to order.

    When it came time to change the shims, do them one at a time and start with one that is going to be re-used elsewhere and replaced with a new one.
    That way you only ever have two buckets and shims out at any one time.
    Be methodical, that's all it needs and check your notes.

    When I'd replaced each shim I put the smear of moly grease over the valve top, placed the shim, replaced the bucket and put the smear of moly grease on top.
    IMG_20131031_145740.jpg
     
  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Once they're all done, for re-assembly it's the reverse.

    I placed a smear of moly grease on both tips of each lower and upper retainer shell edges. This engine hasn't been run for literally years and is bone dry.

    IMG_20131031_150823.jpg

    Turn the stator slightly backwards - counter-clockwise and re-insert the exhaust cam with the alignment hole pointing upwards.

    It won't sit flush down into the cylinder head as there's two lobes pointing slightly downwards onto their respective buckets

    Then advance the timing slightly and reinsert the intake cam, check the orientation -> alignment mark.

    Now that this stage I had my exhaust cam out by one tooth, difficult to tell for sure before reassembling fully - however no big deal.

    Put the locating dowels back into their respective holes and proceed to re-install the upper retainer shells and upper chain guide

    Work end to end on each pair of bolts and use a screwdriver socket drive, keeping an eye on the retainers going down straight. I took up the slack then added 1/4 turn for each bolt before proceeding to the next one

    IMG_20131031_155116.jpg

    One side will go down first because of the depressed buckets, just take your time and it'll all go back together very nicely.

    Once they're back down, retard the timing slightly and re-insert the exhaust side chain guide then return it the stator to zero - TDC.

    Now you can just discern the exhaust cam 1 tooth out in this shot, so I had to remove the chain guides and rotate it 1 tooth forward - I hadn't tightened the bolts down at this stage any more then hand tight with the screwdriver socket handle.

    IMG_20131031_151824.jpg

    Process: remove upper chain guide -> rotate stator counter clockwise to give the exhaust cam some slack, remove the exhaust chain guide and lift the chain and move it one tooth on the exhaust cam - DONE!

    reverse the process. Exhaust side chain guide - upper chain guide - stator back to Zero - TDC #1 firing.

    The last steps are tighten the retainer bolts in two to three stages to the final torque which is 7.2 ft/lb.
    Then re-install the cam chain tensioner, depress the small ratchet and shorten it. Put the allen bolts back into place then re-install the springs and retaining bolt and washer.

    Then you can rotate the engine a few times with your hand to check for no binding resistance and back to TDC #1 firing and verify the cam alignments marks.

    Final step is to verfiy the clearances
    IMG_20131031_161738.jpg
    Combined feeler gauge fingers
    IMG_20131031_161805.jpg

    IMG_20131031_161756.jpg

    All in all it took me much longer to write this than it actually takes to the do the job - it's that easy.
    Be methodical, double check measurements and notes and save drinking beer till after you're done and it'll all go well.

    I have some photos still to take and add to the first segments of this, but all told you should be able to get by just fine without them

    peace out and happy measuring

    Glenn
     
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  7. 150ona250

    150ona250 Member

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    Very well written. Thanks muchly.
     
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  8. Anne K

    Anne K Member

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    How could you tell the exhaust cam was out?
     
  9. Anne K

    Anne K Member

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    I’ve been trying to put mine back together after replacing the shims but it’s just not working
     
  10. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    It helps to fit the exhaust cam first. All the chain slack must be on the inlet side. Run the chain over the exhaust cam and bolt it down in the correct position, then do the inlet cam after. The chain must be tight over the cam sprockets and all the slack on the inlet side where the tensioner goes. Once you have both cams in, fit the tensioner and manually extend the ratchet, fit the springs and bolt.

    Then gently rock the crankshaft back and forth slightly until you hear the ratchet stop clicking. Rotate the crank forwards one full rotation and check the timing marks.
     
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  11. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    There's the dot on the top of the LHS - cylinder 1 when you're facing the front
     
  12. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    You can also wind the stator backwards just a bit to get the necessary chain slack to get the cam in the correct position and into position, then put the stator back to the TDC mark and check the cam TDC position
     
  13. Anne K

    Anne K Member

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    Turns out... I had the timing right.. but I’ve jammed the chain somewhere. Going to pull it apart later tonight, find where it’s jammed and repeat the process again.
     
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  14. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Jammed the cam chain? I don't think it has enough slack to be able to jam.
     
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  15. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Wondering if it's dropped below the crankshaft end and doubled up a link
     

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