Power loss, got hot, cut out...

Discussion in 'Mech Tech' started by GRINNER, Apr 27, 2016.

  1. Right! Sorry I've been busy.

    Finally changed the fuel pump (still mechanical) and gaskets. While I was shopping I got new spark plus, dizzy and rotor arm and changed them;

    Sounds good...

    ...went for a drive and it's still spitting out oil! I me opening the throttle on the drive clearly isn't putting enough stress onto it see the oil coming out!!!
  2. Going back through your photos, it looks like the oil might be coming out from behind the crank pulley.

    It doesn't look like you have a crank case breather (maybe I just can't see it in the photos). If you don't oil may be making its way out behind the pulley due to case pressure.

    Do you know if you have the standard oil thrower ring, or if its been bored out for a rubber type seal as part of the rebuild?
  3. ah, no I can see there is one, looks like it might be a bit small - what diameter is it?
  4. Did you change the old cruddy oil for nice new 20w50 (correct) oil. Lots of threads/posts on the forum to do with failed pumps, repro ones are carp. Think of going electric.
  5. Excessive crankcase pressure, perhaps? Might explain bubbles at the fuel pump pivot - that must mean air is being forced out here, and perhaps also oil being forced out behind the crankshaft pulley.

    If so, check oil breather hose is clear to a good diameter and ideally connected to the carburettor side of the air cleaner for a bit of suction. If you take the oil filler cap off and close with your palm (engine cold or just warm only!) do you feel air pressure?

    I'm wondering if one piston or its rings has been damaged, leading to uneven firing and excessive blow-by...
    dubsurftones likes this.
  6. Finally I get to play with it...

    The diameter of the breather is 10mm and is clear. Holding my palm over the oil filler I get a positive amount of air pressure pushing on my palm.

    Do o need an oil breather kit? I've seen the EMPI for £35 on just kampers, are they any good?
  7. I would have said that air pressure against your palm indicates the breather is not doing its job by applying a slight vacuum to the crankcase.
    zedders likes this.
  8. Ideally it shouldn't chuff at all. As one piston goes one way another goes the other way - equilibrium - any chuffing is combustion forcing itself past the rings.

    So you're attempting to cure a symptom. The idea of the breather is to let the carb suck and cause slight -ve crankcase pressure which helps keep the oil inside. It's not really meant to deal with chuffing.
  9. So is it really a piston ring problem?
  10. Compression test would give you a good idea ..

    paradox likes this.
  11. How have you run it in? 1,000 miles on an engine the rings may not be fully bedded in, which might be adding to your crank pressure....
  12. ...and now my starter motor is jammed. Well I think it is, getting an amusing machine gun noise.
  13. Charge your battery and check connections. :)
  14. Do they cancel out exactly? When a pair of pistons is at TDC/BDC they are separated by twice the length of the conn rods because the rods are horizontal. When the same pair are mid position the conn rods are no longer horizontal and so the pistons must be separated by less than the twice their length. So the volume of air in the crankcase will be greater at BDC/TDC than in mid-position. Or am I wrong?
  15. I still think I'm right. Otherwise explain why mine doesn't chuff at all, I can't even feel it on the back of my hand.
  16. Dunno. Mine has good compression and you can definitely feel a pulse if you put your hand right over the crankcase breather outlet on the oil filler so the air can't escape.
  17. Corroded cable?
    mgbman and zedders like this.
  18. Ha! It starts again.

    One small victory.
  19. Compression test results!

    Number 1

    Number 2

    Number 3

    Number 4

    There maybe some inconsistencies in my recording, but I couldn't get number up at all. Piston ring?

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