Compression question, yet another...

Discussion in 'Tech Area' started by Kansas Corey, Sep 13, 2018.

  1. Kansas Corey

    Kansas Corey Member

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    Good morning everyone! Last night I was able to spend some time tinkering around again. With the startor removed as well as round cam cover off, I was able to actually understand how the adjuster works.

    On my 1979 version, I removed the adjuster cap (next to the oil drain plug) and unscrewed the adjuster screw. The cam chain tensioner has two springs internally and a black plastic/rubber tip on it. I also have the adjust screw and lock nut on the side of the engine. Just describing because I'm not sure all years are the same or not.

    What I did notice was that prior to disassembling, there was quite a bit of slack when turning the stator by hand at Valve Overlap. I checked it all out, cleaned up a few things, then reassembled, and finally adjusted. Took out quite a bit of slack and looks like it's still within correct parameters - it's almost like someone previously managed to adjust incorrectly and left it really slack.

    Next steps are the put everything back together, fill it with oil, and start it back up. My plan is to re-adjust the valves cold and then re-adjust the cam chain tensioner while hot. Probably should timing as well. Anything I'm missing at this point? If not, will update this weekend most likely.
     
  2. racerx

    racerx Administrator
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    If there's anything you're missing, at this time, it's the cause of that much chain slack. Chains don't really stretch, the pins & rollers wear. So a "stretched" chain should be considered worn out. The oil pump sprocket still looks good, in the photo I've viewed; thus, I'd expect the cam sprocket to be fine, as well. That leaves 3 polymer parts: roller, idler, tensioner piston cap. The idler doesn't look like new. The roller is ossified, to some extent...and may be eroded from the chain whipping around inside the tunnel. And I can guarandamntee the tensioner piston cap is brittle. After 39 years and an indeterminate number of heating cycles, those parts don't owe you anything. Happily, they don't cost much.

    You could R&R those 3 parts, leaving the chain in place. Removing the tensioner arm should allow just enough slack...probably more than the bare minimum, due to chain wear. The chain might be okay, can't make that call from behind a desk. I'd replace the chain. It's not going to add any time, or postage cost, to the parcel containing the other 3 pieces that really should be replaced as S.O.P. Last I looked, $18 bought a new OEM chain. With the stator out and the cam cover off, engine on the bench, it's never going to be easier, or more convenient, to replace these wear parts.
     
    Gary likes this.
  3. dirtbkr188

    dirtbkr188 Active Member

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  4. Kansas Corey

    Kansas Corey Member

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    Thank you RacerX and dirtbkr188 -- will look at getting the parts ordered and installed. Just want this thing to run as good as physically possible!
     
  5. racerx

    racerx Administrator
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    ...for as long as possible.
     
  6. ctbale

    ctbale Member

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    Kinda late to this party but wanted to add: When I adjust the timing chain I always have the engine close to TDC or at the end of the compression stroke. I can feel it thru the kickstarter with the spark plug in. Just want both valves closed so the valve cam is "relaxed"

    Then I back off the 12mm jamb nut, unscrew the set screw about 1 turn, pull the plug beneath the eng (14mm?) unscrew that "spring nut" let the 2 springs fall out, then take a phillips screwdriver and press hard on the pistion that has the rubber cap on top, I press hard enuf to feel the squish of that rubber cap, then I release the majority of the pressure, hold up the screw driver with like one finger, just light pressure. then screw in the set screw to hold the piston.

    I am assuming you have the set screw. I dont like the auto tensioners. Your relying on those two wimpy springs and that chamber gets filled with oil to help hydraulicly lock that piston up to keep chain slop to a min. I dont think that chamber sees oil pump pressure, oil just fills in there from the case.
     
  7. cjpayne

    cjpayne Well-Known Member

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    I guess my way is a little odd, but it works for me. I get the bike level, engine up to full temp, and where it's idling steady, then adjust it to where it idles the fastest. Its easy to adjust it to where it actually slows the engine down and then back up from there. I guess its a tuning kinda thing where it works with the least friction.

    One thing I like about the auto tensioner's is that when you hear the dreaded rattling, you know its time to replace the chain.
     
    #47 cjpayne, Nov 10, 2018
    Last edited: Nov 10, 2018
  8. ctbale

    ctbale Member

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    I think the way you described is how the honda manual says to do it .... I think. I tried it that way once and the chain got super noisy. I must have had air in that chamber or the springs were weak.
     
  9. red69

    red69 Well-Known Member

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    I don't think air pressure plays any part in the tensioner.
     
  10. ctbale

    ctbale Member

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    No, your right. I was just saying that maybe there was air under the piston where the springs live. That area should have solid oil, and its ported to the oil sump. It acts as a dampener helping out those springs with sudden "hits' from the chain
     
  11. red69

    red69 Well-Known Member

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    So, basically it acts as a snubber as used in a hydraulic system?
     
  12. ctbale

    ctbale Member

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    yea, needs that snubbing property to assist the springs. Its not filled with oil px from the pump, just fills up from oil sump thru a little hole. That little hole is a restricted orifice providing snubbing.
     
  13. hrc200x

    hrc200x Active Member

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    There is a post about this maybe from Kirrby, Thought it was determined that it is like oil pressure that helps push up on the cam chain tensioner, not pressure from the pump but crank case pressure. I've had bikes that when they start up cold you can hear the cam chain noise a little, then in 5 seconds it goes away.

    Found it, this link, page 2 starting at post 27. https://lilhonda.com/index.php?threads/random-questions.17955/page-2#post-154430
     
    #53 hrc200x, Nov 12, 2018
    Last edited: Nov 12, 2018
  14. ctbale

    ctbale Member

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    Hmm, that's interesting. I followed an oil pump flow chart a few years ago, and it didn't go there but yeah, i can see case pressure pushing oil in that area, never thought of that.
     

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