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Valve Adjusting 101 - General "WHY" and "WHEN" questions

Discussion in 'The Garage' started by wiltony, Jul 19, 2007.

  1. wiltony

    wiltony Will Tony What?

    Joined:
    Jun 22, 2007
    Oddometer:
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    Boise, ID
    I'm new to cycle maintenance. I've been doing lots of reading and reviewing of tutorials, etc. and can do a few things like chain adjust/lube, oil/filter, air, and a little bit of carb work.

    This question on valves, however, is more of a general "why" and "when" rather than a "how." I've seen more than a few valve tutorials, and so am confident on how a valve adjustment works (measure clearance and replace shims to spec). But I haven't been able to find a source as to WHEN (other than the normal maintenance intervals) a valve adjustment should take place, and the reason WHY it needs to be done.

    For instance, I understand when a chain needs to be tightened and what can happen if it is not. I understand why a carb needs to be cleaned, and what will happen if it is not cleaned.

    But I need some help with the following:
    - I DON'T understand how valves slip out of adjustment
    - I DON'T understand how to tell when they might need to be checked or adjusted (without actually pulling the top and checking the clearance)
    - I DON'T understand what can happen if they never get adjusted
    - I DON'T understand how they affect the performance of the bike

    Also I read that they tend to close over time, right? And therefore, when adjusted, should be adjusted to the upper end of spec, right?

    Please, if anyone can help me out with some of this valve theory 101, and help address my ignorance, I would be so grateful! :bow

    (I have a general understanding of how a four-stroke engine works, so you can start from there, you don't need to start with how gasoline is flammable) :D

    Thanks,
    - Wiltony (a newbie who's working on losing that title)

    (disclaimer - my exposure to tutorials and maintenance is limited to the KLR)
    #1
  2. bryantjt

    bryantjt Long timer

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    I believe its a matter of over time the valve face and the head wear at eachother hence the valve stem rises higher and your clearance lessens. Beyond that I've no clue.
    #2
  3. matey peeps

    matey peeps Bead Buddy

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    How valves slip out of adjustment - through wear, clearances will generally tighten as the valve beds itself with the head.

    How to tell when they might need to be checked or adjusted (without actually pulling the top and checking the clearance) - They might be noisy (too loose) or the bike could lose compression or overheat (too tight)

    What can happen if they never get adjusted - valve clearance is set because metal expands when it gets hot. If the clearance is too tight, the valve won't seat fully in the head. This can cause loss of compression, or even destroy the valve by overheating because the head acts like a heat sink to dissipate the heat from the valve. If the valve can't close fully, it won't have the opportunity to lose heat to the head.

    - How they affect the performance of the bike - Again, too tight, loss of compression and performance. Too loose, noise and damage from excessive clearances and metal bits slapping other metal bits. To an extreme, if too loose the valve won't open fully or in a timely fashion and the engine won't breathe optimally.

    When I do valves, I put them at the looser end of spec.
    #3
  4. markjenn

    markjenn Long timer

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    Good explanations.

    Valve adjustments are PREVENTATIVE MAINTENANCE. This means that nothing untoward will occur immediately if you skip the adjustment, but extra wear/tear will occur over time, just like skipping an oil change. And just like oil changes, the bike doesn't really have any way of telling you that the maintenance needs to be done. Yes, the valves can become noisy and yes, you can start losing performance, but once these things occur, more than likely, you've done some damage.

    The reason valve clearances are a precision tolerance is because of the way cams and valves interact. At valve opening and closing, the cam has "takeoff and closing ramps" which gently (relatively speaking) lift the valve off the seat and gently close it. Let clearances open up too far and the ramps leave the picture, so the valve is "slapped" open and closed. This is hard on the valve and valve seats and causes increased cam and valve wear. And once this increased wear pattern starts occuring, then the problem gets exponentially worse. For this reason, the old adage "a loose valve is a happy valve" should not be carried too far. Certainly it is better to be slapping the valve open/closed with loose clearances rather than having things so tight you that you start losing compression (and overheating the exhaust valve since they need to be closed to disipate their heat to the head), but proper clearance is the mfg-specified clearance.

    The adjustment interval is not sacred. It is just what each mfg things is a good compromise between the cost/trouble of doing the adjustment vs. the increased risk of a valve problem or decreased engine service life. You can half the interval or double it and move the compromise to anywhere you like, but generally, unless you have a lot of data, it's best to just stick to the mfg's recommendations. But if the adjustment inteval is 15K, it probably matters little if you do it at 12K or 18K.

    I'd be cautious of people on the net saying "they never go out of adjustment" or "I checked mine at the adjustment inteval and they were Okay, so you don't need to." Everyone's experience is anecdotal and just because someone didn't have a problem at 15K, doesn't mean you won't. It's a statistical thing.

    I've also noted that many who say their valves never need adjustment are folks who have their dealer do it; conversely, those who find they do need adjustment often do the work themselves. Coincidence? I don't think so. I wouldn't be surprised if 50% of the shim-type valve adjustments are "pencil whipped" by the dealers or they do the check and unless something is REALLY out of whack, they just call it good to go. I'm always VERY SKEPTICAL of any dealer who charges a very small amount for a valve adjustment or has a flat rate whether they need adjustment or not. The difference between a valve check and a valve adjustment on most bikes these days involves pulling cams and it is a LOT of work and a lot of opportunity for a tech to really screw things up. It's tough being a dealer these days and many cut corners.

    Just my $0.02.

    - Mark
    #4
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  5. Raphy

    Raphy Adventurer, eh?

    Joined:
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    Mark - some good points you have there especially when referring to the dealer doing the valves, etc. I bought a 2005 bike a few months ago with only 700 km on it. I broke it in and after the break-in stage (1600km) The manual calls for 1st service and a valve check.... When I called around to several DEALERS and inquired about 1st service... NONE of the dealers mentioned valve adjustment or even checks... so i highly doubt that they do them (even if it's stated in the manual) --- I called around several shops, and the honest ones told me this:

    " i'd love to get you in the shop for a 3 hour job and a $300+ bill, but in all honesty - you will not need to look at the valves until about 15,000-20,000 km" - so personally, i won't be touching the valves until that milage... but i guess that's a risk i'm taking...


    BTW - Good topics guys !! !! :clap
    #5
  6. fixer

    fixer KLR-riding cheap bastard

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    hard starting can be a sign or tight valves.

    on the KLR, the 500 mile break in, and then 6,000 mile intervals after that seems to work. there's no real change to the valvetrain on the new, '08 KLR even tho they changed the service interval in the manual, so i'd still check with the old interval.

    if the valve clearances get too tight, the edges of the valves can get beaten to a knife edge and crack.

    if your clearances are too tight, the engine can't breathe properly.

    valves should make some noise, but too quiet, or too loud ain't good.
    #6
  7. dwayne

    dwayne Silly Adventurer Supporter

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    One sign that I notice that my intake valves are too tight is that my gas milage starts to suffer.

    Depending on the bike you may notice the valves tap slightly when setup correctly. Changes to that sound may indicated adjustments are required.

    Familiarity with you bike will help you diagnose valve clearence issues, until then follow the manual and even check (adjust) them a little more often than required. Getting into your valves also give you the chance to take a look see on other areas of your engine.

    The only way to be sure that your valve clearances are in spec is to pull the cover and measure them.
    #7
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  8. SIKLR250

    SIKLR250 NYC

    Joined:
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    +1

    I've had two KLR250s, have checked the valve clearances every 1000-1500 miles and the adjustment intervals have been very different for both the intake and exhaust valves. Same bike, same rider, same fuel. Different models years...
    #8
  9. wiltony

    wiltony Will Tony What?

    Joined:
    Jun 22, 2007
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    99
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    Boise, ID
    Wow, thanks for all the responses, this is very enlightening.

    Now, a bike can make a ton of different sounds. How can you guys tell when the valves may be clacking, versus something else making some noise? Just experience and familiarity with your bike? Or is there something more to it?

    Also, if valves close over time, clacking should lessen and go away, rather than appear and get worse, right? How often do valves go loose? Therefore, poorly adjusted valve symptoms will mostly be limited to tightening of valves, resulting in poor MPG, overheating, and lack of compression, rather than increased clacking, right?

    For instance, I recently bought a super sherpa for my wife, and it makes some engine clacking noises. Not too bad, but enough to make me go "what is that clicking?" Valves were done at 600mi per the previous owner, and I bought it at 4000. If valves close over time, then even if the clearences were set loose, they should've closed up somewhat between then and now, so I shouldn't be hearing clacking, right? It is safe to say, then, that the clacking is not from the valves? (matey peeps, maybe when you're through here, you could listen if you have a sec)

    Also, when I start a valve adjustment, I will probably need shims. Do ya'll just buy a full set of shims? Or do you order them one by one, once you've measured and know what you need? (meaning potentially days with your bike apart, waiting for shims to be shipped?). How does that work? What if you need two of the same width of shims? Where do you get them, and about how much should I expect to pay?

    BTW, anyone in the Boise area who might be doing a valve job, please consider inviting me to shadow (or I'll do it and you can shadow). I'd love to get some hands on experience before I try something like this on my own.

    :bowThank you ADVers for sharing your wealth of knowledge and experience! :bow
    #9
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  10. SIKLR250

    SIKLR250 NYC

    Joined:
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    Here's some Super Sherpa shim info:
    http://www.sudco.com/75valveshims.html

    I'm soooooo glad that all of my bikes have had screw/locknut-type adjusters. Wouldn't buy a bike without them...
    #10
  11. tenere660aus

    tenere660aus Adventurer

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    Roma Qld
    I'm soooooo glad that all of my bikes have had screw/locknut-type adjusters. Wouldn't buy a bike without them...[/QUOTE]

    I adjusted my valves today (all tight) and can't help thinking that there are some jap designers still laughing about how difficult they made it. Atfer removing tha tank, seat, sidecovers, fairing, radiator etc there are two small holes between the motor, frame, cables, wires where you insert a spanner, bent feeler guage and some obscure special tool and operate them all with the two fingers that can reach them and you may as well close your eyes because you won't see what you are doing. thats just for the exhaust side, the inlet has an allen head bolt that doesn't have enough room for a second bite with the allen key. And this should be done every 6000km, I am too scared to ride it again.
    #11
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  12. kawalaser

    kawalaser Hip to be square

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    My klr just hit about 1500 miles and I've noticed now that the valves have begun to make a little noise. Should I get them checked or is this normal?

    Thanks
    #12
  13. kawalaser

    kawalaser Hip to be square

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    Bump.


    It it normal for a KLR's valves to start announcing their presence after the break-in period or what?
    #13
  14. kellyk7

    kellyk7 Who knows

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    This may start a firestorm of controversy but.. I say adjust them,, I have always taken the vew on mechanical tappets and these are, that you adjust them every time you tune.. with screw adjust rockers it is snap easy,, I am in the middle of a week long mess adjusting the valves on my Yamaha with shim and buckets, I assure you I will not adjust those, but my XR650 with screw types, I run them when ever I service the filters, plugs and such. It works out to about 100 to 150 miles of trail, it takes about 20 mins, on top of the time it takes to get the gas tank off.

    I have never run the valves on a KLR but,, if it is easy then do it often, to me I like a quiet motor, one that ours,, I am getting used to it on bikes but
    #14
  15. kellyk7

    kellyk7 Who knows

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    I adjusted my valves today (all tight) and can't help thinking that there are some jap designers still laughing about how difficult they made it. Atfer removing tha tank, seat, sidecovers, fairing, radiator etc there are two small holes between the motor, frame, cables, wires where you insert a spanner, bent feeler guage and some obscure special tool and operate them all with the two fingers that can reach them and you may as well close your eyes because you won't see what you are doing. thats just for the exhaust side, the inlet has an allen head bolt that doesn't have enough room for a second bite with the allen key. And this should be done every 6000km, I am too scared to ride it again.[/quote]

    this almost sounds easier to drop the motor and then adjust the valves,, then reinstall the motor..
    #15
  16. kellyk7

    kellyk7 Who knows

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    I am in the middle of a week long valve adjust on a FZR1000 and every one of the 20 shims was tight. My local dealer said no problem 8.00 each, one of the performance shops said bring them in and swap them for the ones you need at 3.00 each.. my Wife said "What?!!!!! more money you just spent your free cash on that Jacket and Pants, figure out how to do it cheap"

    So my solution, a knife sharpening oil stone and a micrometer,, this does however give me the advantage of being able to set them exactly where I want them,, not like it will really matter on a 18 yr old bike.

    by the time I am done I will have tied up about 20 hours in this job.
    #16
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  17. ibafran

    ibafran villagidiot

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    amazing!!!

    i would have thought that the shims had some sort of hardening on the faces. the cam face is hard, aint it? the shim needs to be hard, doesnt it? the wearing surfaces need to be oiled to keep the wear to a minimum.

    the shims are supposed to be hard enough that they can be swapped?

    If one abrades the hardness off the shim with an oil stone, wont the durability of the shim be so compromised that it cant be trusted to last very long?

    maybe one ought to be sure to abrade only one side of the shim and install it such that the cam does not run on the abraded side.

    rumor has it that some of the automotive valve shims fit bikes at a big, big savings. if i had my shims out and clearences measured, i would visit several auto dealerships with a few shims to see what might match. worth a few phone calls, i would think.

    waddaya tink?
    #17
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  18. johnjen

    johnjen Now, even more NOW!…

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    Ding, Ding, Ding we have a winner.

    Some still want to learn this their own way. It can get expensive when you have to replace (not swap) not only the shims but potentially the cam as well.

    JJ
    #18
  19. kellyk7

    kellyk7 Who knows

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    OK I am new to this... :ear Fill me in.. A quick search of both this forum and Google I found a lot of references to "fine tuning" shims by sandins them down on 320 to 400 grit wet dri paper.

    Cam does not run on the shim, the shim runs between the Valve stem and a boss on the inside of the bucket, the bucket is hardened, the shim is hardened and the valve is hardened. I assume the valve rotates, and the bucket rotates, mostly together but may not always,, there was no oil stain on ther face of the shims, but some on the sides.. this would indicate that there is some rotation diference and some abrasion. but the etched number was still visible on each shim.

    most of the shims required 2 to 3 thousands to get into the spec.

    then of course there is the seat of the pants assesment,, I did not notice even on the shims I had to take off .005 that they cut any quicker at the end then they did in the begining. I would think a full hardening would be easier on a thin shim..

    Last thing is,, this is a bike with 150K + miles, and more of a learning bed, how long is it gong to take to gall up those shims. ?
    #19
  20. Kerry_129

    Kerry_129 semi-reformed squid

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    Pretty safe bet that the shims are 'through' (probably induction) hardened rather than having just a 'case' hardened exterior.
    The only potential problem I see with grinding them down, is that they undoubtedly have slightly convex/non-parallel surfaces now. Enough to cause a problem? I think probably not, but personally I think I'da coughed up the ~$60 to swap them - that's a lotta PITA hand grinding! :lol3

    As for shim-under-bucket vs. rocker/stud design - the shim under bucket is a far more robust, efficient, and compact design with lower friction/parasitic loss and fewer parts/wear surfaces. It generally allows far higher RPM with less wear & much longer adjustment intervals. A couple of years ago I did a buddy's '97 VFR with 45,000mi on the clock which had never been checked, much less adjusted (I believe the recommended interval was 12~16k, I know my '01 is 16k). IIRC, with a .006(in)/.009(ex) +/-.001" (actually .02mm/.0008") spec, two were ~.001" outside spec, and 4 or 5 were .001" off 'center-spec'. I doubt that an 'old-school' rocker-arm valve-train would have survived that long unattended, much less held that close to (a very tight) tolerance - and the top of the head would need to be a good bit larger to accommodate the additional bits, and the 13,000rpm redline would have been a good bit lower.

    Hell - if maintenance ease is the measure of what's mechanically worthwhile in an engine, why not just stick with externally-adjustable pushrods? :deal
    #20
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