Valve Clearance Question

Discussion in 'Technical Help' started by Cyborgbot, Mar 16, 2019.

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  1. Cyborgbot

    Cyborgbot Guest

    My Tiger 800 XRx is hurtling towards its 24k mega service - that includes doing the shims...

    I really don't ride the bike hard, just a lot... As an example, the tyres and chain sets lasted 18500 miles. The chains I replaced not because of sharks teeth on the cogs or overly stretched chain but because it was getting a tad stiff in places... Other than that it was reasonably in good order. The tyres were getting squared off on the rear and there were some alarming 'cracks' in the front - but other than that they too were totally legal with tread to spare.

    This made me wonder if the shims would wear differently depending if the bike was red-lined 24/7 vs gently driven by a boring fart. The 12k check (if it happened at all - another story) showed everything was well within tolerances (like new).

    What are the symptoms of 'badly' worn shims? Knocking noises? Is there anything really bad going to happen if I run the bike to 30k or 35k without changing them? I am sure there must be a way to put some sensors on the engine and tell if they need doing.

    So, how critical is it to change the shims?
     
    • Agree Agree x 1
  2. Richard Neale

    Richard Neale Active Member

    Apr 20, 2018
    156
    43
    Northwich
    Quite often The wear is more on the valve seat than the shins or cam lobes etc so they actually close up and go quieter... Seems you are riding really gently and if you are accelerating gently and not reving hard it would be reasonable to extend the inspection period .. my fireblade has 19k and has never been checked and has been used hard. But it's a cheap bike and apparently they hardly ever need attention... Fingers crossed... So I guess your decision could be helped by finding out how common it is for the shims on your model to need adjustment . I bet you get a lot of mpg too !
     
    • Like Like x 1
    • Thanks Thanks x 1
    • Agree Agree x 1
  3. Wishbone

    Wishbone First Class Member

    Nov 4, 2018
    861
    643
    Essex UK
    The problem is: were the clearances set up correctly before?
    First check is vital!!
    Either check them yourself or have it done, but ask for the values when checked!!
    They close up on wear so as said don't think a quiet engine is a good thing unless it is from a position of knowledge;)
     
    • Agree Agree x 2
    • Thanks Thanks x 1
  4. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,444
    1,000
    Norfolk UK
    Actually the valve train is under more stress and therefor wear at lower RPM and idle, as said it the valve seats that get hammered and therefore shim clearances close up, and in fact you more liable to cause damage to valve seats if they get to the point where the valves are held slightly open, IE if on exhaust side the valve can burn out and if inlet it will cause bad running,
    so although unlikely unless high mileages are involved it always best to check, and if a mileage service is specified it because the engine designers think it wise to do so given the motor spec.
     
    • Agree Agree x 5
    • Thanks Thanks x 1
  5. Tiglet

    Tiglet Vintage Member

    Mar 28, 2016
    4,433
    1,000
    Cheshire
    I always remember being told years ago that a noisey valve(screw and lock nut adjustment in those days) is a happy valve :)
    A tight valve is a unhappy valve and this what you’ll get as the shims wear :(
     
    • Thanks Thanks x 1
    • Agree Agree x 1
  6. Cyborgbot

    Cyborgbot Guest

    If I might summarise...

    1) A tapping / quiet value doesn't necessarily indicate a 'happy' or 'sad' valve. If it's the valve seat that wears, they close up - how do you fix that?!?

    2) Reving the tits off an engine doesn't wear the shims more than driving like a vicar on the way to a parishioners for afternoon tea.

    3) I could probably get away with extending the service (shim) interval a little since the test at 12k was showing no signs of wear.

    4) They should make engines last longer with lower maintenance...
     
    • Agree Agree x 1
  7. Wishbone

    Wishbone First Class Member

    Nov 4, 2018
    861
    643
    Essex UK
    But you bought a bike with the spec and maintenance intervals it has so stop whingeing about what manufacturers don't do or forget their intervals and hope for the best!!
     
    • Agree Agree x 1
  8. Tiglet

    Tiglet Vintage Member

    Mar 28, 2016
    4,433
    1,000
    Cheshire
    A contributing factor in valve seat wearing can be down to tight clearances (a sad valve) and therefore quiet, if they had a bigger clearance than spec they would be noisy.
    How do you fix that,,,,,,,get them checked as the manufacturer recommends ever 12000 miles if your concerned.
     
    • Thanks Thanks x 1
    • Agree Agree x 1
  9. Cyborgbot

    Cyborgbot Guest

    ?!?

    I didn't realise I was whingeing (sic) about the manufacturers' service intervals. I do the servicing myself as the bike is out of warranty - so other than parts, it is just a few hours of interesting mechanics which I am happy to do.

    The manufacturers are however well known to support their dealers and the maintenance side is a money maker for them. Being an engineer I understand there are situations where it is imperative to do the servicing by the book as massive safety margins are needed for compliance to regulatory directives - eg aviation and the nuclear industry - the use of manufacturer parts and the like are compulsory and you replace critical parts even if there is no apparent wear. Indeed some parts are taken back and examined to see how they have worn and denatured through stress fatigue.

    Servicing a car / bike is not even remotely the same. Let's face it, the first thing most people know about a problem on their vehicle is when a warning light comes on or the MoT test picks something up - then they fix it - things 'break' that aren't on minor/major service interval checks. This might not be the case so much with new cars where people tend to take them into a main dealer regularly to keep their warranty valid - or say changing a cam belt where the materials used are perishable and a catastrophe failure is an expensive mistake. However older cars are often driven till they 'rattle' and if lucky given an annual service just before the MoT - you don't replace an exhaust after 'x' many months or change the bearings speculatively - you wait until they show wear. Wear is variable upon use and conditions, and the cost of servicing becomes ridiculous vs the value of the vehicle.

    My question was a thought exercise about general wearing of shims and so tried to seek herd wisdom of the forum and asked if a gently run engine's valves wear less than those in a thoroughly twatted (but enjoyed) engine.
     
    • Like Like x 1
  10. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,444
    1,000
    Norfolk UK
    #9 Tricky-Dicky, Mar 16, 2019
    Last edited: Mar 17, 2019
    (edited as i just noticed that my spell wrecker has change engineer to beginner...sorry!)

    But being an engineer you would surly know how and why valve clearances need to be checked and why they change so why ask a question that you would know the answer to?:confused:
     
    • Like Like x 1
    • Agree Agree x 1
  11. Cyborgbot

    Cyborgbot Guest

    I was trying to get a 'finger in the air' opinion from others about their experiences with changing shims. I don't know of anyone that needed shims changing at 12k which is the first major service on a Tiger 800, and have only heard of only a few needing shims at 24k (even then not on all cylinders). However my data sample is small and statistically of little value.

    It doesn't take much to get people cross :) I thought this was an innocent question...
     
    • Agree Agree x 1
  12. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,444
    1,000
    Norfolk UK
    Who's cross? it just seems to me that the time is takes to wip off the cover and check clearances with a feeler gauge is worth it for piece of mind...especially since you do your own servicing and maintenance anyway.
     
    • Agree Agree x 1
  13. Cyborgbot

    Cyborgbot Guest


    I’m lazy... And procrastinate. And would rather avoid doing the (any) work if it absolutely doesn’t need to be done.


    As you say, it’s not hard - and if I’ve bothered to lift the tank I’ll rerun the sound bomb hose as the sodding thing keeps popping off the pump, and there are some electrics that need a bit of a tidy - there’s a photo of a wiring birds nest on the forum somewhere.

    Still interested to know how many people needed new shims though at 12/24k, and if riding style makes a huge difference to the wear in a motorcycle engine...
     
    • Agree Agree x 1
  14. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,444
    1,000
    Norfolk UK
    Cant help in fist hand knowledge of wear characteristics of that engine but for most others its more a case of regular essential maintenance and oil and filter changes that will determine the wear rate rather than the riding style and mileage...unless of corse its regularly over revved or labored in high gear and apply 's to all engine types.
     
    • Agree Agree x 3
    • Thanks Thanks x 1
  15. Yorkshireman

    Yorkshireman Crème de la Crème

    Dec 12, 2015
    3,401
    1,000
    Barnsley
    I think the only way to answer the points raised in the initial post, ie does the valve gear wear more if revved hard as opposed to used gently, would be to forensically check a sample number of engines before and after such use to see how each had faired. I agree with pretty much all that has been posted about this type of valve gear apart from post #4, how does the valve suffer more wear at idle/low rpm?
    Anyway FWIW I’d check them at 24k regardless of how the bike had been revved. I’ve just done mine at 12k (1050 Speed Triple) and only one was slightly tight, but in tolerance. If I’ve still got the bike at 24k then I would expect that one will need attention. I sought the advice of a friend who runs a bike shop about the valves and he said they would be ok, years of experience can’t be beaten, but since I had the airbox off to change the spark plugs as part of a winter 12k service, it made sense for me to check them. Now I know what condition they are in I can forget about them.
     
    • Like Like x 2
    • Thanks Thanks x 1
    • Agree Agree x 1
    • Disagree Disagree x 1
  16. Rocker

    Rocker Elite Member

    May 1, 2016
    1,662
    800
    Suffolk
    Check them they're probably ok but then you'll know how the engine is wearing and may help you decide to or not at the next interval:) I'm sure there are plenty of engines that have never been checked still running just fine
     
    • Thanks Thanks x 1
  17. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,444
    1,000
    Norfolk UK

    The valve train IE cams, cam chains, rockers, push rods etc etc are operated at half engine speed and as a result are subject to more mechanical stress partly because of this and the fact that it takes more
    force to move this kind of mechanism and in consequence is also subject to more wear as a result...its a well known fact try asking and engine designer/engineer
    rather than a pall who's run a bike shop for a few years...
    Its a misnomer that engine wear because of high RPM as i said before an engine will wear faster if its idled for long periods and labored at low RPM and high loads.
     
    • Thanks Thanks x 1
    • Disagree Disagree x 1
  18. capt

    capt Elite Member

    May 8, 2016
    3,052
    750
    western Australia
    It's true though, valves and cams take a lot of energy to open/turn , and they wear more at lower RPMs because oil flow is less at speeds just above idle ! Higher Rev's increases oil flow and pressure significantly ! More oil more slippery nuf said. The valve surface wear is affected by many things, fuel conditions, air/exhaust/engine temperature, if the clearances too small gases flow through whilst still burning hot ! Or inlet side will flow back causing incomplete induction causing poor power and running ! If the engine is "popping" or "chuffing" valves are too tight ! Popping is exhaust & chuffing is inlet...
     
  19. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,444
    1,000
    Norfolk UK
    The faster an engine runs the less stress its under (providing its all balanced correctly and modern manufacturing methods ensure that) its all down to reciprocal force its far easier for an engine to run at faster speeds as it requires less force to keep the RPM up and so more fuel and power efficient, (obviously if its running at too high RPM IE beyond its limits it will of corse take more wear, but that not whats being discussed)

    Its only friction that effects wear so the more stress applied to any moving part the more wear it will take as a result, lubrication obviously plays a big part but as long as the part has adequate lubrication this is not a problem until the force involved overcomes the oil barrier that wear becomes a problem.

    It a well known fact that all engines suffer more wear on cold start because its relying on oil cling/shear for the first few seconds before oil pressure builds enough to keep all the moving parts centered on a cushion of oil, the slower an engine runs the lower the oil pressure and this in turn more force is applied because of the reciprocal mass is more at low RPM, this applies to the whole engine and because of the configuration and lower speed more so for the valve gear.
    Load is the engine killer in respect of wear, not RPM...which is one of the reasons gears where invented.
     
    • Like Like x 1
    • Disagree Disagree x 1
  20. Cyborgbot

    Cyborgbot Guest

    Interesting - assuming the engine is running warm and the oil pressure and flow is at its normal operational level for any given RPM, there should be sufficient lubrication (if the engine is designed well and oil/filters are effective and well maintained). As the engine revolutions increase, more oil is needed to maintain the appropriate level of lubrication - drop the revs again and the oil pressure will drop back to the amount of lubrication suitable for that RPM. There would be a lag in rev increase and more oil being delivered - that could cause wear - especially in a cold engine (newly started). Too little load (reving without any load) would also probably not be particularly good for the engine components.

    So back to my thought experiment - two engines - one rev'd a lot at the lights, red lined and regularly driven in low gears to get high revs/power must turn many more times for the same milage than an engine that has been docile, warmed up gently and driven in a higher (but appropriate) gear - but without excess load or strain.

    We can see the effects on chain, sprockets and tyres - a more enthusiastically ridden bike would change these components miles before the sedately driven bike due to the additional stresses - my logic is that maybe the same wear profile would exist inside the engine. The recommended maintenance intervals for checking may have been evolved for a 'slightly enthusiastic' rider (maybe even a worst case scenario) to provide a safety margin that would identify shims that needs to be done. It would however be problematic for Triumph to say "if you ride like a loon at 100% RPM then check the shims after 12k miles, an average rider at 16k miles and someone who drives like a wet blanket at 20k miles..."
     
  21. Yorkshireman

    Yorkshireman Crème de la Crème

    Dec 12, 2015
    3,401
    1,000
    Barnsley
    The "pall" (sic) you refer to is a Honda trained mechanic who's run his own successful business for 30 years or more. I sought his advice about the valves simply in passing as I was buying new spark plugs.
    I know that an engine left idling is not good news as is making an engine strain at low revs/ high loads but when you say an engine is under less stress the higher it revs has left me thinking I'm better off leaving this thread. Cheers.
     
    • Like Like x 1
    • Disagree Disagree x 1
  22. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,444
    1,000
    Norfolk UK

    You misquote me i actually said that the valve train was under less stress at high RPM, but its true that an engine used at the correct engine RPM for the load will be under less stress regardless of RPM within its designed limits.

    And i am not talking out of my ass...i have been building both bikes and cars including building and tuning engines since i was 16...quite how a trained mechanic can state that the valve train is not more stressed at low RPM than high is beyond me and would make me doubt there expertise regardless of them being a mate or not.
     
    • Disagree Disagree x 2
Loading...

Share This Page