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Solved Identifying random engine hole

Discussion in 'Technical and Troubleshooting Torque' started by DanCobby, Aug 19, 2016.

  1. Can anyone help me identify what is meant to go into this hole on the front of my 79 cb750k dohc? Ive searched high and low on the net, found a few photos that just have a blank hole. I have seen that there are different models that have oil coolers there.

    Needing help as I have noticed a very small amount of oil leaking out of the hole

    Attached Files:

  2. Looks like it might have held the end of a mechanical tacho cable. Some old bikes had them driven off the crank, others from the cam.
  3. We thought that might be the case but the tacho cable goes into the cam on this bike.
    Thanks though
  4. I would have guessed it was an oil pressure test port, but looking at the oil flow diagram it seems not (the fact that its up on the cylinder head and not of=n a main oil gallery on the engine block also suggests it is not.
    Tacho drive seems to be up on top of rocker cover more toward the middle of the four cylinders.
    • Like Like x 2
    • Agree Agree x 2
  5. You can see the inside end of it here, it is inline with the chain that drives the rear (intake) cam off the front (exhaust) cam. Inspection seems unlikely, tensioner is possible, or to insert a threaded tool to lock camshafts for chain replacement or timing adjustment or similar.
    • Informative Informative x 1
  6. Looking at the workshop manual the Col Coleman linked to, is it the oil feed entry from the engine block via that pipe and banjo bolts?
    Is this engine running?
    • Like Like x 1
    • Agree Agree x 1
  7. I've had a better look and it's where the cam chain tensioner rod goes as already noted by the Colonel and jstava :)
  8. Thanks everyone, when i got the bike it was full of silicon (quality). I degreased and gernied the engine and although tried to avoid the "plug" the inevitable happened and got spat out.
    The engine does run, its a little rough though. It cam with pod filters on the standard carbs which I have found out from research, the carbs dont run well with pods.

    This is my 1st road bike, I have had motocross bikes in the past. But this is a whole new step for me.
    Thanks for your help guys
  9. Here is a close up photo of the hole 20160819_174212.
  10. That's what she said
    • Like Like x 1
  11. Best part about owning shitty and/or old bikes. You learn to be a mechanic. If I was to add up all the "experience" i have gained from my bikes, I should be nearly 400 years old.

    I am a firm believer of if you are not competent enough to work on your ride, you aren't competent to ride it. Enjoy your journey of enlightenment grasshopper.

    • Like Like x 2
  12. and this is why I will never own a Ducati
  13. Don't you want to be a desmo maestro?
  14. I'd be happy to learn, but I don't have the time or money to cock it up. A motor with regular valves will survive a slightly bad clearance job and chuff or rattle it's distress pretty quickly but won't detonate or snap valve stems. Screw up a desmo valve clearance job ... that's some bad mojo.
    • Funny Funny x 1
  15. Sorry. Just replied in your build thread. It's just a plug part #91208-422-003

  16. It is a hole to be proud of.