Oil pressure light ficker at idle - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 46 (permalink) Old 06-12-2017, 11:54 AM Thread Starter
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Oil pressure light ficker at idle

Hi,
I fitted an oil pressure switch to my '68 T120 rebuild to give me some indication of any impending oil pressure issues while I'm riding. However, when the engine is hot after a run and the bike is sitting idling (1000 rpm), the oil light flickers very slightly - in bright daylight you wouldn't even notice it as the light doesn't reach full brightness. As soon as I raise the revs by just a tiny amount, the light goes out and stays out as long as the revs are over 1000, but the light flickering comes back once the engine returns to idle.
I checked the oil pump during the rebuild and got good suction on both bores of the pump. The oil return to the oil tank looks 'normal' (regular 'spurting' at idle but a good solid stream when the throttle is opened up).
Does that flickering light sound 'normal' or am I looking at an oil pressure problem? The bike runs brilliantly with no nasty noises or oil leaks so I'm hoping that it's just 'one of those Triumph things'.

Thanks
Tony
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post #2 of 46 (permalink) Old 06-12-2017, 12:24 PM
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How many miles are on the motor???
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post #3 of 46 (permalink) Old 06-12-2017, 12:38 PM
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If you are worried about the oil pressure, test it with a gauge.
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post #4 of 46 (permalink) Old 06-12-2017, 01:12 PM Thread Starter
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The engine has 6 miles on it.
I don't have an oil pressure gauge (yet) that's why I was asking the question - if it's 'normal' I can leave getting a gauge until my bank balance has recovered from the rebuild :-)

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Tony
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post #5 of 46 (permalink) Old 06-12-2017, 01:23 PM
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Depending on oil viscosity the pressure can go quite low at idle, i would always rather go with a pressure gauge, that way you know where you are at all RPMs.

“One who enjoys finding errors will then start creating errors to find.”
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post #6 of 46 (permalink) Old 06-12-2017, 02:08 PM
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Hi tjwood, Light should not flicker at 1000 rpm whatsoever.

Either the sender is bad or you have low oil pressure.

You really need to test pressure with gauge, but you could replace sender & see what happens for the price of a sender.

I was doing experiments with the flicker on my bike. I idle around 1100 fully warmed motor (after 30 miles freeway ride). If in gear I let clutch out & almost stall motor where motor is going kachunk, kachunk almost at the stall point the light will flicker at ever kachunk. Maybe 200 rpm??? Pulling in clutch oil light goes out instantly. Again it never ever flickers under normal conditions. Not even at night when flicker would show most. Even at 6-800rpm no flicker.

Doing same stall test on cold motor light will never flicker. Remember the sender has a pin hole for oil access so the pin hole acts as a damper somewhat.

I'm using Mobil 1 v-twin 20-50 oil.

Don

Last edited by TR7RVMan; 06-12-2017 at 02:09 PM. Reason: added sentence
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post #7 of 46 (permalink) Old 06-12-2017, 03:02 PM
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Hi Tony,

Quote:
Originally Posted by TR7RVMan View Post
Light should not flicker at 1000 rpm whatsoever.
If you look in the '69-on workshop manual, you'll see tickover pressure should be about 20 psi; otoh, the switch turns on about 7 psi ...

Quote:
Originally Posted by tjwood View Post
I fitted an oil pressure switch to my '68 T120 rebuild to give me some indication of any impending oil pressure issues while I'm riding.
About as much use as a chocolate fireguard. Given the pressure it switches at, if the idiot lamp comes on when you're riding, the plain bearings in the engine are already donald. It's actually an "Engine fcuked" lamp/switch.

Bear in mind what's a 'good' or 'bad' pressure depends on rpm - as I say, tickover pressure should be about 20 psi, but that's pants at normal riding rpm. Put it another way, given the myriad speed limits in GB, would you replace the speedo. with a lamp that turned off at 7 mph?

Hth.

Regards,

Stuart
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post #8 of 46 (permalink) Old 06-12-2017, 06:43 PM
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I would try another switch first on your bike.I have never had an oil gauge but do have that red lamp.It goes off when i start and stays off until the engine stops again with no flickering.It has come on twice over the years when out on the road.First time was the crank end oil seal inverted,second time was a snapped crank.

Now,where did that bit fall off ?
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post #9 of 46 (permalink) Old 06-12-2017, 07:04 PM
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I have been involved with three bikes with this problem. Two were mine one was a friends.


1 Cylinder Head was loose. Tightened head bolts problem solved


2 Oil pressure switch was damaged (bent). Therefore it was giving a false reading


3 Oil Seal in Timing Cover was in backwards. Did you replace yours?


K

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"THE WORLDS PRE-EMINENT MOTORCYCLE"
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post #10 of 46 (permalink) Old 06-12-2017, 07:24 PM
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Are you using a good grade of motorcycle specific 20/50 oil. The older types are better for the Triumph air cooled engines. Also, I believe that the idle should be at 1,200 rpm. My '70 Tiger would show a "flicker" at 1,000 rpm after a hot run...............in the garage, not outside in the sunlight. I set the idle at 1,200 and it cured it. The bike is still running fine for my friend who bought it 3 years ago.
Just the "village idiot's" take on it, that's all: Jim

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