4th Gen idle hangs

Discussion in '3rd & 4th Generation 1990-1997' started by dgp, Mar 2, 2021.

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  1. dgp

    dgp New Member

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    I was not using a torque wrench at that point, I had previously tightened down the cam holders using my 1/4” 10mm socket and when the caps reach the mating face of the head, then I used my torque wrench. I certainly would have stopped if I thought something was not right, this is an expensive mistake.

    Interesting to note about the spring loaded cam gears. After I calmed down a bit, I put the broken cam back in (it’s still in one piece), but did have to use a screwdriver to line up the gears and it tightened down no worries.
     
  2. dgp

    dgp New Member

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    So, Honda Australia told me these cams are no longer in production, and there is no stock available.
    I found one cam in the Netherlands at CMS, listed as their last one so jumped on it. I have also purchased a set of rear bank second hand cams from the USA. It could be 4 weeks before I get this back together.
    My plan is to use the second hand cam to put it back together and make sure I don’t have another problem, if all good, I will put the new cam in the motor, then re-do the shims on that cam.
    Question, do I need to run the motor to recheck the shims if I replace the cam, or is it still ok to turn it over by hand a couple of revolutions to seat everything?
     
  3. squirrelman

    squirrelman Member

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    curious .....did you rotate the crank (even a little) while you had the cam out ??

    ALWAYS rotate the crank over at least 4 revolutions by hand after shim changes.
     
    Last edited: Mar 19, 2021
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  4. dgp

    dgp New Member

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    Squirrelaman, I honestly can’t say if I did or didn’t rotate the crank when the cam was out, although I am 99% confident that I didn’t.
    After tightening it all down for the first time, I rotated the crank by hand for 3 or 4 revolutions, must have been 4 to get me back to TDC on #1 compression.

    Do you have any pointers in running in a new cam, bearing in mind I have to first get the bike to idle and possibly sync the carbys on first start up too?
     
  5. squirrelman

    squirrelman Member

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    i can't tell what went wrong but guess that possibly a mistimed cam lobe was pushing on a valve that was in contact with a piston, in which case you have a bent valve in addition to broken cam. hope not, but it's hard to understand the actual cause of a broken cam. it was a good idea to use a 1/4 "-drive setup, but i doubt any serious damage could be done unless you torqued to much more than the standard force of 10 ft'-pounds on the cam holder mounting bolts..............?

    carb can be bench-synched close enough to run ok on startup. align all throttle plates to just barely reveal the first progression hole, starting with the carb the idle speed adjustment screw touches.

    good luck :Rolleyes:
     
    Last edited: Mar 20, 2021
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  6. RllwJoe

    RllwJoe Member

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    Wow!!! Sorry to hear that. I hope it all comes together for you soon.
     
  7. dgp

    dgp New Member

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    Hi all, my new cam arrived and I wanted to get some advice before I go trying to put it all back together.
    In the photos attached below, i have put the broken IN cam back in place on the rear bank, but it is in the exact position it was in when I removed it. You can see the location of the lobes on #1 and #3 IN and EX, as well as some pretty hard to see IN valves on #1 and #3.
    My question is about TDC and the #1 and #3 valve position.
    I thought I had placed #1 at TDC in the compression cycle, but am now second guessing myself due to the broken cam issue I experienced.
    In this position, all buckets can rotate freely, on all cylinders except for #3 IN, which has the valves slightly open (on overlap?).
    Is this normal, or have I got this wrong, which caused me to break the cam?
    When #1 is at TDC on compression, should all buckets be loose?

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    Last edited: Mar 28, 2021
  8. dgp

    dgp New Member

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    Ok, another update.
    The brand new cam arrived from the Netherlands to Australia in 7 days , but I waited for the second hand cam from the States, just to make sure I knew what I had done wrong in breaking the original cam.
    I installed the second hand cam, buttoned it up, checked clearances and all was good in the world. I decided just to run with the second hand cam.
    While I was waiting for the second hand cam, I removed the forks and dismantled them, sending the lowers out for powder coating, and also replaced the head stem bearings with some tapered units. Geez, it wasn’t until I had all the load off the front end I realised how bad the head stem bearings were, they must have been the originals, they had rust through them, and had worn divets in the races. There were several notched resting places for the steering if you wanted to ride in a continuous arc.
    I also pulled the instrument cluster apart and cleaned out 25 years of dust, the white line across the tacho in the picture is a reflection of the light in my shed above the bike.
    Put everything back together, I went with the stock 1 5/8 turns out on the pilot screws, bench synced the carbys befor installation (thanks Squirrelman) and they only needed very minor adjustments once once the bike to balance them.
    Unfortunately it’s raining here today, I have have brand new Pirelli Angel GTII’s on the bike, so the shake down ride will have to wait.

    I really appreciate the input and information from the forum members, thank you very much.

    E938F8B2-3D10-46A4-B16E-34D88D8BB8DC.jpeg 33CDB193-2607-45E8-9687-891E4D1A430B.jpeg 895D9746-3A5A-4600-953E-714E9B1D38EE.jpeg 2DC9986B-CC69-4A02-9404-AF8806954FDE.jpeg 91D48F47-6A85-49CC-9BF7-6065523D5E2B.jpeg
     
  9. squirrelman

    squirrelman Member

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    good work. remember new tires are slickery and need breakin.
     
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