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Old 10-08-2012, 08:11 AM   #1
chasesa OP
Joined: Feb 2009
Location: Stephen Chase Fredericton, NB Canada
Oddometer: 16
R100GS oil light flickering

My 1990 GS oil light flickers when driving. I realize this can signal low oil pressure but I'm interested to know anyone's experience with faulty indicator lights. I have just replaced the sender unit.nsame flickering.

On removing the filter, all O rings are ok and in place.

Your advice please.
Stephen C
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Old 10-08-2012, 08:39 AM   #2
Anatomically Correct
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Joined: Sep 2008
Location: Chicago-ish
Oddometer: 14,862
The light, if it illuminates, if fine . . . . . if you get flickering on the oil (pressure) light using two different sending units, and you have checked the wiring, I would bet you have low oil pressure.

this can be caused, of course, by having too little oil in the reservoir/engine . . . . I assume you've checked?
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Old 10-08-2012, 09:38 AM   #3
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Joined: Nov 2009
Location: Hiding off Hwy 6, B.C.
Oddometer: 4,744
Very easy to connect a proper gauge on them. That way you'll know for sure. Them oil pumps can push over 100 PSI cold. The idiot light, altough I don't have the specs here should come on at around 12-15 PSI. Lots of bad things can happen to them engines between 15 PSI and the normal operating oil pressure.

That would be a better question for the Airheads in Old's Cool then they can go on about the proper mounting/measurements of them oil filters.
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Old 10-09-2012, 04:58 AM   #4
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Joined: Aug 2005
Location: Ontario
Oddometer: 2,044
There are people out there saying that when the oil lights comes on flickering it's already too late. My advice: do not ride the bike, find the cause. Start wit the obvious (enough oil, no leaks), then measure the oil pressure. My 1000cc engine pushed up to 160psi cold and settled to 20psi @ idle and 60psi @ 4000+ with the engine at operating temperature.

How to build a cheap and cheerful oil pressure meter in 5 minutes under $30:

  • a 1 1/2" oil pressure gauge from your local hydraulic supply, 1/8NPT fitting, 160psi range, 270deg sweep (my preference)
    => $5.50
  • a tubing kit with 3ft-4ft of 1/8" nylon tubing and at least a 1/8NPT Male and one 1/8NPT Female fitting (e.g. EQUUS #9801)
    => $9.10
  • one adapter fitting M12x1.5 Male to 1/8NPT Female (to fit the original location of the OEM oil pressure switch)
    => $9.40
  • one 7/8" hose clamp
    => $3.50

Oil pressure gauge on the bike:


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Old 10-09-2012, 10:11 AM   #5
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Joined: Aug 2010
Location: Mid-South, M-town
Oddometer: 626
Does the same light in the dash light up fully if you short the oil pressure sender lead to ground? If not, it's likely the oil and charge bulbs got swapped at some point.

If the right bulb fires above, it's time to measure your canister depth and adjust the filter gaskets/shims accordingly.
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Old 10-09-2012, 10:39 AM   #6
Boxer Metal
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Location: Chico, California
Oddometer: 3,570
Add an extra shim behind the white o-ring and see if the problem goes away.
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