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Valve Shim Clearances - Worse That Could Happen.

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by T.Depta, Jan 3, 2009.

  1. I am fast approaching that time when one should have the valvestem clearances seen to. I don't know exactly what it involves but its something to do with checking the tappet clearance or something relative to the valve stem end thingy.

    My question: what happens if i leave it for longer than the recommended service interval?

    I'm asking because I (try to) do all maintenance work myself. What does one actaully 'fix' when doing a tappet clearance? i know it has someting to do with the cam shaft but i don't understand why. Isn't the cam shaft lobes always in contact with the tappets?, so why does that need to be a clearance gap for the valves?

    Going to a mechanics is tha very last thing I want to do. I'll learn before I give it to someone and throw money at them to make the problem go away.

    My bike is an 06 VTR-250 currently with 11K on the odo and bought secondhand from a dealer with 4K on the odo with only one official service. I so far have done; many chain clean+reoils, oil+filterx2, brake pads F&R x1, radiator flush x1, carby-cleen-juicex1, new tyres F&R (balanced at shop, however).
    I want to learn how to "do valves". I know how an engine works and all that, also.

    In the future I'll be doing an air filter change (very soonish since my fuel consumption is creeping up: 3.8L up from 3.5L/100km), will do my own clutch plates replacement and further down the track a chan+sprocket replacement.
  2. If you're not familiar with the concept of shims and valve clearances you're probably better off getting a bike shop to do it for you.

    The shims are like 2 dollar coins in size and shape. They vary in thickness and as such you need to know what the current gap between the cam and the shim is. if the gap is say, 2mm and it is supposed to be 1mm then you need to get a shim that is 1mm thicker than the current shim.

    Repeat for the number of valves that need adjusting.

    The methods of retaining the shims vary from manufacturer to manufacturer. Suffice it to say, you will most likely need to obtain a special tool in order to depress the valve and one to extract the shim.

    If you do your measurements using a set of feeler gauges and go away and buy the shims, then come home and fit them and discover that the shim isn't quite right you'll need to go back out and return the shims and exchange them for the proper ones. This could be an expensive exercise, not to mention time consuming. The cost depends on the supplier of the shims, I s'pose.

    Getting serviced by the dealer means that he'll have all the shims on hand. He'll exchange your originals for the new ones. Dunno what sort of discount you'd get if your shims are still servicable.

    Oh, the 1mm and 2mm figures are examples. Actual clearances would be in the order of decimal points of a millimetre.

    If you let them go the worst that can happen is that the engine gets a "tapping" rhythm going. It shouldn't affect performance nor reliability. But it's a timely reminder to get it done.

    Cost-wise, dunno. Probably around the $500 mark once you factor in time, parts, etc.. That is what I was quoted for a service for the Blackbird, which has shims. Previous Hondas that I've owned had locknut adjusters which I did myself.
  3. The valves don't seal properly and the engine runs like crap (low compression = low horsepower).
    Of course get the clearances wrong and there's a chance the valve may get intimate with the piston - in which case it's goodbye engine.

  4. We charge $10 per shim, change over.
  5. Get the service manual for your bike.
  6. If ya dont know what your doing and dont get it right its going to cost ya a heap of bucks :wink:
  7. huh ok never figured out why shims are so pricey doing 16 of them aint fun.
    i got quoted 12$ per shim

    Shim kit should cost you about 160-230 AUS$ from the USA.

    8 shims in a vtr

    if u can find TDC and re assemble your timming chain ect and pull the cams and whatever else needs pulling out on your modle you should bew fine
  8. The reason that you should pay attention to your valve clearances, is because the valves slowly eat their seats, thereby reducing clearance. The valve eventually doesn't close properly, which is the start of some headaches for your bike, and you.

    If you want to do it yourself, take the time to get it right, or you will have to make the time to do it twice.
  9. Service manual.

    Read everything you can about it and have a shot. Ideally find someone on the forums savvy with it and you'll be sweet. Once you've found TDC correctly you're laughing.
  10. Service manual at $125....

    HA! I don't think so.

    I had just tried google, this site with all its old/dead links and of course Honda. The closest I got was to the Spada service manual which is not the same, although people have said it is. Six gears vs five!

    Can someone recommend me a site where i can buy the physical manual or even a paid download in Australia for a reasonable price? The spada manual (althought incorrect) was terrible quality which even if it were the right one...

  11. Of all the bikes I've had, none have required having their shims changed when checked. You should be able to check the clearances without specialist knowledge, but the actual changing may be best left to a mechanic. Unfortunately, unless you really don't want to spend the money, it's one of those things that you should have done professionally.
  12. You can download the manual from a number of torrent sites.
  13. Got my e-hands on a service manual and the common service manual. Had a quick look at the procedure. Looks complicated :eek:.
    It seems that the MC15 engine uses locknut valve clearance adjuster thingys instead of shims. I'm going to have to take a day off and learn it slowly by playing with the engine.

    I guess if its out of my league I'll just pay someone to give me a head job! :oops:
  14. Well, you're away.

    Alls you have to do is adjust the retaining nut and you'll have some play. Make sure you have found tdc and then just stick the feeler gauge in etc. Easy!
  15. If it's screw and locknut adjusters, it's bloody easy, once you know how.
  16. It's easy in theory and a little more frustrating in practice.

    Once you find TDC, (and the correct TDC) use the correct size feeler gague to check the gap between the rocker arm and the head of the valve stem. If the gap is too big or too small adjust it.

    To do that loosen the lock nut then turn the adjusting screw in or out to open or close the gap. The gap is right if you can can still slide the feeler guage but you can feel it start to grab. No grab then too loose. No slide then too tight.

    Now comes the hard part. Tighten the lock nut without changing the gap. Not as easy as it sounds.

    Always, always recheck once you have tightened as at least when you first start to do it, you will probably have let the adjustment move as tightened the lock nut. If so, go back and do it all again. Keep doing it till you get it right.

    And if you can't get it right, then better slightly loose than slightly tight.
  17. Thanks for that advice.

    I was actually starting to think how can i annoy you guys further by asking which would be better if i couldn't get it spot on? Looser or Tighter gap?
    Logic dictates that larger gap is better since tappet tapping would be better than floating valve heads getting a bad heat treatment. Obviously the best would be the recommended gap clearance, so I'll aim for that.
  18. front and rear pads for a vtr250 with only 11k on the clock. you must ride her hard :) .

    Be sure to read the manual carefully and only adjust the tappets on the rock. may require different revolutions for exhaust and intake clearances.
  19. I give a fanging!

    I broke off the hero knobs within one week of owning it on my L's!

    ...and no, it wasn't from dropping it :LOL:
  20. As long as it's on the compression stroke, that is...