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valve/shim adjustments....why?

Discussion in 'Cruisers' started by jphanna, Oct 24, 2011.

  1. hi people,

    when i bought my eliminator i was told that i need a shim adjustment every so many kms (6000?). so that doubles the service from $200.00 to $400.00.

    so i am doing my researce on a new bike, now that i am off restrictions. a suzuki M50 i am told, has the same set up, every second service, a shim adjustment is needed ($400.00 min) dont know yet if the kawaski vulcan custom needs this, as that is one of the bikes i am looking at.

    why dont cars need shim adjustments every few thousand kms? my jet ski doesnt even need shim adjustments?

    is this all Mbike brands or just a few?
  2. My hyo had them every other service- so every 8000. the honda is alot more i think every 24?
    i think its to do with the tuner level compared to cars. ie. a bike is tuned alot more and therefore higher tolerances are needed.
  3. Ouch that hurts.
    Does it say in the manual every 6,000? for valves. I spose mmm maybe. Still most are around the 12 or 24,000 k's. Your basic service is every 6,000. They don't do the shims every service.
    Look in your book. It will have a dot on how many K's it should have to do the valves.
    The shimms are the spacers for the valves so they open and close to the correct measurement.
  4. well if you don't like the idea of paying to get your shims done then you can either do it yourself or get a bike with an engine with easier valve adjustments, for example the DR650 has an adjustment screw that you just turn with a special tool to adjust the valves.
    the answer to "why" is because if you run your bike with the valves out of spec, then you'll bugger the top end up I think, and lose power.
  5. Its a part of motorcycle ownership.

    If you dont like getting you fingernails dirty either give up bikes or pay for a mechanic to do it.
  6. To properly explain all this would take several pages.

    Most cars have hydraulic tappets, which are self adjusting. As a rule, that technology works well in engines that rarely get over 3,000 rpm, but works badly or not at all on engines that routinely get over 10k.

    Older bikes, or bikes built in a lower state of tune often have a screw and locknut arrangement for valve adjustment. Many older jap cars also use a system like this. It makes adjustment easy and cheap, but it adds weight to the valve assembly, limiting the ability to run reliably at high revs. It works well up to about ... say 8k.

    For valves that need to work reliably, for long periods at high revs, you use shim under bucket adjustment and bear directly on the bucket with the cam lobe. This has the disadvantage that if you inspect the valve lash and find one that needs to be altered, you need to take the cam out to do it. That's a big job.

    As Kernel said, if you run the engine with the vale adjustment wrong, it's bad. Too loose will result in damage and rapid wear to the valve system, and too tight will result in burned valves and burned valve-seats.

    more on the way...

    The interval between regular valve checks varies from model to model. It has very little to do with brand. It has a lot to do with what that bike was designed to do, and how valve actuation works for it. As a rule, big twin cylinder cruisers rev slowly and many of them have some form of automatic valve adjustment. Same with some big touring bikes. Check this before you buy the bike, and factor it into your purchase decision.

    There are bikes which are cheap to run, but they tend to be small and utilitarian and not very exciting. Most of the bikes people buy because they like bikes (as opposed to because they want to commute cheaply) are not cheap to run. There's a line in the car world about how if you have to ask about the fuel consumption, then maybe you should consider a cheaper car. In the bike world, I'd relate that to tyres and servicing. Find out what that's going to cost before you buy the bike. The figures will probably shock you if you haven't looked into this. Bikes cost much more to run - as a percentage of their initial purchase price - than cars.
    • Like Like x 3
  7. i do my own oil changes, in between factory services. i have also changed the clutch cable. thats about the limit of my technical ability.

    thanks for explaining about the reasons. it makes more sense now, but as mentioned for cruisers, they are not high reving. adjustments shouldnt be as common on those.

    anyway its a toy, and toys are $$$$. just have to suck it up i suppose.
  8. I doubt it would need 6,000. 60,000 I would believe and there is easily 2 hours more labour involved, so that explains the price.

    On something like a cruiser sensible design would dictate screw and lock nut for and OHC engine, but that doesn't mean any engines on the market will have it. Screw and lock nut is easy to do yourself and can be done on a Saturday morning.

    Shimming is annoying as a self servicer, because it's impracticable to have a full shim kit sitting at home. You need to pull it apart, take measurement, go and get the shims, if they've got them in stock, come back and replace. It means your bike is out of service for days.

    I don't' know why more engines are not screw and lock nut. The GSXR1100 was good to 11k. That means shims should only be on race replicas. Shims are just lazy design or a ploy to get more service work.
  9. OTOH, shim adjusted valve clearances tend not to move about much after intial running in. My BMW K100 never changed in 80,000 kms. So even though it's a good idea to check the clearances at or around the factory service intervals, there's a very good chance they won't need adjusting which is the bit that tends to require either special tools or lots of dismantling.
  10. At 6000 Km I would expect it to be screw & locknut, not shim & bucket adjustments.

    My TRX has shim & bucket adjusters, good for 24 000 Km.

    If it's a locknut system, it's easy.