Erratic Oil Gauge

Discussion in 'Oil' started by 90FXRS, Jun 13, 2017.

  1. 90FXRS

    90FXRS Junior Member Contributor

    492
    28
    10
    2001 Twin Cam B. Had a collapsed lifter. After a lifter replacement the oil pressure gauge is not acting the same as before. Use to top out at 60psi or so when it was cold no matter how much rpm. I'm assuming it bypasses some how. Idled at 25 when warm. 52 when riding and warm. Now when it's cold, when you blip the throttle, it will swing to 70 or so. Doesn't do it all the time. When it's warm, idle pressure is lower than before. Riding pressure is around 40 or so.

    Bike has a new set of Wood Alpha Series lifters and existing gear-driven cams. Adjusted 4 turns with 32tpi pushrods. Ran a couple of hundred miles, readjusted. Fueling cam support and oil pump.

    Thanks up front.
     
  2. Jeff Klarich

    Jeff Klarich Experienced Member Contributor

    6,027
    183
    881
    Sounds like the gauge is not reading correctly. My engine is modified and my oil pressure at idle with a warmed up engine is about 8-10 psi and at cruising speeds it climbs to 32-34 which I think is normal.

    You may want to try an alternative mechanical gauge and compare readings.
     
    Last edited: Jun 13, 2017
  3. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    4,649
    83
    223
    Like Jeff suggests, hook up a known good gauge and see what happens. Is the oil pump/cam plate new? That plate and pump will certainly produce a much different pressure than stock. Could be the bypass valve is sticking but I would go with known good gauge for proof first...
     
  4. 90FXRS

    90FXRS Junior Member Contributor

    492
    28
    10
    Everything is the same as before except the lifters. The one that collapsed looked to be intact, cup was seated squarely and the clip was intact. New gauge is coming, only other one I have is 50psi max.
     
  5. Jeff Klarich

    Jeff Klarich Experienced Member Contributor

    6,027
    183
    881
    Good deal keep us updated.
     
  6. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    4,744
    83
    144
    I agree with what Bodeen said above. Get an accurate gauge and see what the pressure is. If the external gauge reads more consistently at different RPMs, and shows any pressure around 10psi at idle (hot), and not too high on high RPM (hot), then I would suspect the sending unit or the gauge on the dash. Sending unit is a bit easier to change (especially with the tool) than the dash gauge.

    If the external gauge shows inconsistent pressure, then I would suspect the plunger in the plate is hanging up on debris in the port. Not too big a job to remove the plunger, clean it, and swab out the port (especially with a barrel mop). Just have to remove the cam chain spring tensioner to get the plunger out. If the plunger doesn't drop out when the tensioner spring "tail" is out of the way and the plunger spring is removed, use a popsicle stick stuck up into the plunger to snag it.

    Let us know what you find.

    Cheers,

    TQ
     
  7. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    4,649
    83
    223
    Yeah, and when I said gauge. I was referring to a test type gauge. Not something that mounts to the bike.....
     
  8. Jeff Klarich

    Jeff Klarich Experienced Member Contributor

    6,027
    183
    881
    Me too.
     
  9. 90FXRS

    90FXRS Junior Member Contributor

    492
    28
    10
    I've been meaning to get back to this but things have been rather busy here. I finally got in touch with a friend that I thought might have a test gauge. He did. Cold start is a steady 55psi, goes to a little over 60 when you blip the throttle and then, I'm assuming, the bypass kicks in. As it got hotter, the gauge started dropping a little at idle. Rev it up to a steady rpm and she holds at 55psi. After it hot, 205 on the oil temp, it idles at 23psi. So I changed the "worry" gauge and all is well.

    Thanks for all of the input. I was suspecting the bypass plunger but I've never dealt with one. Glad it was just the gauge because I was not really looking to get into the camchest.
     
    NCBILL likes this.
  10. Jeff Klarich

    Jeff Klarich Experienced Member Contributor

    6,027
    183
    881
    Good deal thanks for the update.