Feeler Gauge for valve check

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by skidxr, Dec 14, 2012.

  1. Steveman

    Steveman Been here awhile

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    Being a mechanic myself I can tell you that this is a very bad idea due to the fact that most shims are just hardfaced. At least those used in KTM EXC models so I assume that this also applies for all other KTM shims.

    But I am open to be teached better... Of course I am talking about a shim over bucket config.
    #21
  2. Dustodust

    Dustodust Long timer

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    thanks for the info on hardfaced shims
    yep , I would just put in the correct shim myself
    saw them sanding shims and asked what are you doing
    thats why I dont let anyone work on my bikes anymore
    most of them are expert professionals who know everything
    usually they just charge for the valve adjustment and do nothing
    #22
  3. KtmPedro220

    KtmPedro220 Adventurer

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    Try eBay UK?
    #23
  4. markjenn

    markjenn Long timer

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    Are any new KTM's shim over bucket? Seems like almost all the recent designs are shim under bucket. The only sorta recent engine I recall using shim-over is the ZX11/ZRX motors and these have roots in the 1980's.

    - Mark
    #24
  5. geometrician

    geometrician let's keep going...

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    +1. All shims are hardened. The only time you'd want to hand grind a shim is to gain operating clearance so you can get out of the wilds.

    As for shim over vs. shim under it doesn't matter. The shim faces are still transferring the energy- were not JUST looking at the cam lobe/rocker sliding over the surface (shim over), the head of the valve stem/contact pad inside the bucket (shim under) are going to work/hammer the shim

    Shim over is very old (usually) air-cooled technology. These designs have their roots in the motorcyles of the 1960's and is some cases (KLR650 for one) continue to this day. Most shim-over are 22, 27 or 29mm diameter shims, the shim-under are 7, 8, 9mm by comparison. Most engine designs today stay away from shim-over as there is more reciprocating mass to be controlled which leads to heavier valve springs & more robust valve timing components to deal with the addtional loads
    #25
  6. Peanuts

    Peanuts Long timer

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    250, 350, 400, 450, 500, 530, 690 SX/EXC/SMR/SMC all have a shim sitting on the valve, with a rocker arm operating on the shim. No bucket. Some use same shim as the LC8, but not under a bucket.
    #26
  7. markjenn

    markjenn Long timer

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    Thanks for clarification. I would think this wouldn't have any scrubbing loads like would occur with a cam lobe bearing directly on the shim.

    Like I said earlier, I've heard conflicting views on whether grinding shims is a good idea or not. All over the map on this one, from "shims are completely homogenous and are ground to thickness anyway" to "shims are surface hardened and if you grind off the hardened layer, they'll rapidly wear and cause valve clearances to go way off in a short time". All a shim-under-bucket sees is compression loads and it doesn't seem like a very good application for surface hardening, but I'm not a metallurgist. In any event, I don't grind shims anyway. But I'm surprised there are such differing views.

    - Mark
    #27
  8. geometrician

    geometrician let's keep going...

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    ALL valve shims are centerless-ground to thickness and then chemically hardened which only penetrates the metal in tens of thousands of an inch- not throughout (which would be heat hardening)

    The shims compression load includes taking the hit from (whatever) clearance being taken up as the cam opens the valve- at 6,000rpm that's 100 revs a second, divided by two (720 degrees of crank rotation in a 4-stroke) divided by the two cylinders equals 25 hits a second. Might not seem that the inertial loads of valve, top keeper, retainers & bucket is much but considering they are opening from a dead stop each time it adds up. FWIW most valve wear occurs in the top 15% of the RPM range, so road/drag/supermoto race engine speeds will see wear before someone who doesn't cane the shit out of their engine

    I've taken out shims on customer bikes (esp the 250, 350, 400, 450, 500, 530, 690 engines metioned above) with such a depression hammered into them from the top of the valve stem they are unusable. They do, indeed, wear. Worse case is when the outer edge of the shim contact the spring keepers and the retainers get knocked out of their lock with the valve stem and the valve drops into the cylinder where it promptly makes contact with the piston which leads to bent valve if not valve head broken off stem which REALLY makes a mess! Rocker arms on these engines is required for SOHC (single over head cam) valve actuation, and the arms ("followers") themselves are hardened as well on the modern 250/350/500 KTM four strokes (pretty irridescent colors). The 690 uses rollers on the ends of the arms to reduce angular force acting on the valve/shim- not the perfect solution as they weigh more and the roller/retainer pin wears, which increases clearances/wear.
    #28
  9. markjenn

    markjenn Long timer

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    Do you have any kind of reference from a mfg or other authority?

    Thanks for your informative post, but again, I can tell you that there are lots of equally authoritative posts in other forums that say valve shims are not chemically hardened or case hardened but instead are through hardened, included a few folks who have done tests and concluded that the hardness is uniform throughout.

    This shim kit says they are through hardened.

    http://www.roseville-yamaha.com/esh...oduct_1308333.WISECO174_COMPLETE_VALVE_SH.htm

    I have no dog in this fight since I do not grind shims and am not advocating to do so. I'm just surprised by how little hard information there is on this subject.

    - Mark
    #29
  10. MortimerSickle

    MortimerSickle Semi-Adventurer

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    What I wonder about grinding shims by hand is, how do you keep the surface perfectly flat and aligned on the same plane as the other side?

    I can see that it could be done with careful use of a surface grinder, but by hand I would think it would tend to be uneven.
    #30
  11. Peanuts

    Peanuts Long timer

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    Me too. Makes it an extra pain to reshim as the clearance with the dimpled shim is artificially large.

    I have seen the top of the valve stem bruised so much that the edge had to be ground to allow it to pass through the valve guide.
    #31
  12. Peanuts

    Peanuts Long timer

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    Back on topic...

    Using 2 blades on top of each other is sometimes better than just one thick blade as the combination will flex easier around the cam/bucket area. If you use just one thick blade you can be tricked into interpretting the force required to flex the blade as a tight sliding fit.

    I know cos I did it last night! Using a friends straight blades that I did not want to bend....
    #32
  13. geometrician

    geometrician let's keep going...

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    Every shim kit currently for sale lists hardening in the description

    Here's a post from a machinists forum I just looked up

    As from manufacturer/authority, yes. I've gone to Tech training courses provided by motorcycle manufacturers, apprenticed @ MegaCycle Cams, worked at a shop where we prototyped & repaired cylinder head/valve systems for manufacturers, and have been reading the publications of machinists journals & trade industry newsletters for years. And that's just me. The people I ride with & talk to work for NWI, DARPA, JPL as well as a gear maker from Switzerland whose company provides the machinery for Toyota & GM among others to grind & harden all their transmission gears.

    There is no fight. Just trying to keep mis-information from becoming "internet fact". This forum above all others is (to me) full of the right spirit. When there's something I actually know about I'll contribute- otherwise I read what others are saying & try to pick up the right info from it. As a high-mileage KLR owner I can tell you I don't waste my time on any of the forums dedicated to that bike- too many idiots; too confrontational. If KLR forums are bad, try something gun-related. Too much ego over information. <off soapbox>

    Long Live Orange Crush :freaky

    To be sure you come up with more precise measurements by adding blades, that's why buying a quality set with all the low numbers covered is best. Right now Snap-Ons best set is $13.45 retail and contains 35 blades.

    Not sure what you mean about bend/flex? I always feel the tension on the blade(s) as I remove them from the gap, not pushing the blade(s) into it.

    Ha Ha yeah with some of the modern heads it's hard to get in there to do that job. People who don't work on them for a living don't get to see all the crazy stuff people "do" to their bikes. At the shop & at the home garage I have a "Hall Of Shame" of failed parts that I keep on display to encourage discussion
    #33
  14. markjenn

    markjenn Long timer

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    All well and good, but when the day is done, all you're doing is what I've seen tens of others do on forums of all sorts - say "they know" but can't quote an authoritative source.

    - Mark
    #34
  15. triplenickel

    triplenickel Long timer

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    Ummm that's kinda what forums are all about, have you considered taking the initiative to contact manufacturers yourself? Otherwise you'll probably just question whether someone else did even if they claim to have. Get some literature for us all to see.
    #35
  16. markjenn

    markjenn Long timer

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    All I've said is that there is a lack of hard information. I don't claim to know the answers like some do.

    - Mark
    #36
  17. triplenickel

    triplenickel Long timer

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    I understand what you were saying, I was suggesting if you weren't happy with the answers you got perhaps the source would be another choice.
    #37
  18. Peanuts

    Peanuts Long timer

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    Because the laminate of gauges are more flexible than one gauge. They bend around the cam lobe easier and give a more accurate feel.
    #38
  19. Steveman

    Steveman Been here awhile

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    This is 100% what I have experienced when talking about KTM engines with one overhead camshaft. No experience with the new designed dohc engine of the 350 yet, but for all others what you say is definitely right. I talked to so many smart guys telling me that shims dont wear but I personally have experienced the contrary.

    I also can confirm, that with the config of KTM engines where no bucket is used and the rocker arm is in contact with the shim the engine speeds are the factor. While the valve clearence on bikes used from hobby riders almost keeps constant the valve clearance of bikes revved hard and used in competition needs to be corrected every 10 to 15 hours.
    Thus I can say that two myths concering ohc engines with shims are wrong: valve clearance on ohc engines always changes in one direction (tighter) only - wrong. Ohc engines once broke in and re adjusted dont need valve checks as the clearance stays constant - also wrong. :freaky

    regards
    Steve
    #39