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#763807 01/28/19 9:58 pm
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Last summer I blew an oil line on the 72 and it took about 3/4 of a mile to get to a safe pull off site. Idiot light on all the way. I am about half sure I did no damage, but am afraid to go on the more remote and longer rides I am used to. I put on a cheap OP gauge and it shows great pressure when cold, good when hot at high speed, not so much to zero at idle. I've rigged a "T" so I can run an idiot light and the gauge. Is there a way to test an $18 gauge for accuracy? Next warm weekend in LA I'd like to haul it down there and do some hard tests runs. I've got to know for sure.


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Try a $100.00 gauge That's what I was afraid of. I have not seen a $100 bill since 2008. "The great crash".


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Now wait a minute, why do you have to go to LA?

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Hmm, last summer my bike had a similar issue, unnoticed loss of oil pressure for at least 5 minutes...After looking for the problem and finding none, the oil pressure just as mysteriously reappeared..And the engine had normal pressure. I tore down the engine this winter and there was no bearing damage...John Healy had this to sat about it...

Quote
If the pump fails you will seize the rod bearings from lack of oil. But there are conditions with a Triumph where the gauge could read no pressure and still not seize the rod bearings. This when either the oil seal feeding the crankshaft inverts, someone puts non-timed tappets in an engine set up for timed tappets or the oil pressure relief valve sticks open.

With oil presented to the end of the crankshaft a center fed crankshaft will deliver enough oil in these conditions to prevent the bearing from seizing. At least until the area heats up from lack of oil flow. There will be enough oil to allow the dynamic wedge to form, but not enough flow to cool the rod, and its bearing.


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Now wait a minute, why do you have to go to LA? Because it's warm down there. I could ride around all day up here right now and it's so cold if I had no oil pressure at all it would not matter.
I've got no strange sounds. The motor has always had loud mechanical sounds. But after 34 years I know what sounds right.It's a bit diferant but no rattles or knocking. This old turd has been in five western states and parts of mexico. I'm taking it with me when I go.


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So, what I am going to do is hook up the idiot light and get rid of the gauge. I find my self stareing at the gauge. It's something new and I'm not used to it. I put about 200 fearful miles on it last year before winter closed in. If the light does not come on I'll assume the best. I'll have to wait a bit as winter has come back all over.


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.
Buy another cheap gauge of a different brand
And compare the results .
They don't have to perfectly agree , but if they generally agree
You're on your way to confirming that your gauges are both somewhat reliable
even if not exactly calibrated .

.




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Desco

Rig your cheap oil pressure gauge with some odds and ends - make a temporary tire pressure gauge out of it
at least that way you could check it against an existing tire pressure gauge you have some confidence in

Charlie


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I remember reading years ago the reason behind cars dropping oil gauges. It was that people were fixated with the gauge and would pester the garages if they thought it was too low. The found a lot of engines were being pulled to bits and which they found had no faults. It may be post hoc reasoning for an economic decision to reduce costs by just getting rid of instruments. But there seems to be a ring of common sense to it. We all know of motors that have unbelievable wear, but continue run well. I acknowledge a high performance motor is a totally different beast to the standard manufactured ones.
Another alternative to a gauge is a pressure relief valve from a pre-unit where they had an indicator button that popped out as the pressure rose.


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I was surprised how much engine noise are in these bikes. Hadnt heard it in forty years then rebuilt this bike and I was thinking what’s all that noise ! I checked everything and it was fine. Now I’m used to it.
It’s really noisy when I take my helmet off my ears !

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Hi desco, Please refresh my memory. What was the gauge reading after you replaced the pump & driving block?
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You can buy oil pressure switches that are adjustable but you would need a thread adapter . I think that the Triumph one comes on at about 7lbs psi. I read on this forum that a chap from the factory had said that the introduction of the oil pressure light caused a lot of worries for riders as it was very common for them to come on at low revs. Before, like on my 67, there was no light and no pressure worries! I rode around with a split crank seal for I don't know how long but the rod bearings were fine. Always use the PW ones. The SDA ones are not up to it at this point. I know this from experience.

Dave

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TRman
Cold 87 psi @ 2,000 rpm
25 900

Warm not hot 75 psi @ 2,000 rpm
15 900

I remember the last ride on warm day of about 15 or so miles. Idle was 7 or less.

Again, if the light does not come on after a hard, uphill run on a warm day I'll assume the best.

Last edited by desco; 02/01/19 8:27 pm. Reason: addition

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Originally Posted by dave jones
You can buy oil pressure switches that are adjustable but you would need a thread adapter . I think that the Triumph one comes on at about 7lbs psi. I read on this forum that a chap from the factory had said that the introduction of the oil pressure light caused a lot of worries for riders as it was very common for them to come on at low revs. Before, like on my 67, there was no light and no pressure worries! I rode around with a split crank seal for I don't know how long but the rod bearings were fine. Always use the PW ones. The SDA ones are not up to it at this point. I know this from experience.

Dave

"Worry light" was one nickname... Story is that the pre-war oil gauge was discontinued for much the same reason, people worrying over "lost" oil pressure. Chances are it was a cost issue too, Turner was one to look after his pennies. Anyway, knowing beats not knowing, so if I have any doubts, like desco has, I hook up a gauge to verify. Oil pressure switches are often (usually?) cheap and unreliable, a 7-10 psi switch may well switch at 3 or 15 psi, or not at all. The original switches were actually more reliable than today's I think.

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Here's a tip. The pre unit "tell tale" OPRV does not indicate oil pressure. it indicates that the oil pressure relief valve is being lifted from it's seat. So, with that in mind, it can be seen that any pressure under the relief valve pressure will not be indicated, to a point. I find it pretty common that at idle, hot, it doesn't move at all.

Hey, what? Me worry?

As long as it comes out when I rev it, all is good.

Cheers,
Bill


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Originally Posted by HawaiianTiger
Here's a tip. The pre unit "tell tale" OPRV does not indicate oil pressure. it indicates that the oil pressure relief valve is being lifted from it's seat. So, with that in mind, it can be seen that any pressure under the relief valve pressure will not be indicated, to a point. I find it pretty common that at idle, hot, it doesn't move at all.

Hey, what? Me worry?

As long as it comes out when I rev it, all is good.

Cheers,
Bill


I don't understand what you're getting at here Bill, if it's not oil pressure lifting the valve (and hence the tell tale button) what is?

There are 2 springs in that system, a short weak one, and a long strong one. The weak one allows the button to lift small amounts in response to small oil pressures (and I mean small, so it has a similar meaning to a 7psi switch, except more informative).
When that spring is coil bound, higher pressures are shown by compression of the main spring, and the button lifting by more than about 2mm.
That was the original design. However, subsequent use of different springs and washers can easily result in different behaviour in response to oil pressure. The only way to know what the button means is to compare it with a trusted oil gauge with hot oil.

I know that the centre feed (with or without oil seal) of a Triumph makes it tolerant to low oil pressures, but I wouldn't wish to depend on that in the longer term. The only way you can be sure the crank is receiving more oil than it needs is by seeing significant oil pressure.

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Bring the idle speed up to 1000 rpm.

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Hi desco, Koan58 really hit the nail on the head. "The only way you can be sure the crank is receiving more oil than it needs is by seeing significant oil pressure".

We tend to idle motor a little faster about 1000-1050, or even 1100 in hot weather or motor might stall in city after heat soaking several stop lights in summer.

Even at 100+f fully heat soaked the oil pressure is always above 15# at the above rpm. The oil light never ever winks on or comes on. If it does the motor has low pressure or bad switch.

Riding a while back thinking of oil pressure threads I clutched to motor at a stand still to see what rpm light would come on, with motor smoking hot. Hard to say but around 300 or less. It was virtually at the stalling point. Then with each firing stroke light would go off. I don't know what pounds that would be. I don't know what my switch is calibrated too. I'm not touching it though as I don't want to bring problems on.

Doing that test on '69 Bonnie which has an oil gauge is about 5-13# with gauge flickering. Gauge feed has a tiny pin hole so the needle is dampened to a degree. Bearing clearance on this machine is .0017" with plastigauge. Has late type tappet feed with hollow dowel as yours does. Has original oil pump & drive block in good condition. This is with Mobil1 V-twin 20-50 oil on both machines at same temperature. About 95f that day.

I found V-twin oil to give less pressure cold, but higher pressure hot, than the straight 40w Torco TBO break in oil. 40w was way thicker cold.

I expect heat soaked after say 60 miles in LA area which will be about 70-75f this time of year your pressure will be about 3# at 900. Will be most interesting test. Keep rpm the same as it is now for the initial tests if possible.

Of course at idle the bearings are only supporting idling loads so it doesn't need so much oil. But pulling at lower rpm like stop light to stop light when your only reving 1500-2000 is there an adequate wedge of oil? That I really don't know. Probably??

Very much looking forward to your results. These kind of tests give us important knowledge.
Don


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Don wisely and repeatedly refers to the engine and oil being fully heat soaked for any meaningful observations of oil pressure, as this is the condition that the lubrication system must be designed to cope with.
It is also important that an oil is used that is similar to that originally specified for the engine, say 20/50.
Then, but only then, oil pressure can be a useful diagnostic tool. Significantly lower than expected pressure with the previous provisos then warrants investigation.
Desco's observations so far:
Cold 87 psi @ 2,000 rpm
25 psi @ 900 rpm

Warm not hot 75 psi @ 2,000 rpm
15 psi @ 900 rpm

Desco, is it possible to give these measurements when the oil & engine are thoroughly hot, say after an hour's riding? If possibble, also report pressures at 3K, 4K etc.

One thing that concerns me is your cold pressure of 25 @ 900. (as well as 15 @ 900 warm not hot). I find it takes at least 20-30 minutes riding to get to those levels, indeed cold pressure is pretty much the same at low and higher rpm (~75-85) for 10-15 minutes.
Even with the original pre-unit bush (not the unit oil seal set up) the indicator button would stay fully out for about that period of time, then gradually retreat as the oil heated up.
So IMHO 25 @ 900 cold is NOT good, and as Don suggests, will become next to nothing when fully hot. I think it should be 15-25 psi minimum hot idling.

Assuming main bearings are good, once the pump, crank oil seal (and crank nose surface) and OPRV have been eliminated, it only leaves the big end clearances as a cause (excepting rarities like cracked crank, leaky sludge tube plug, flywheel bolt sealing).

Desco, presumably the feed oil pipe between the tank and engine came off? Do you know why?
If that was the case, another couple of minutes motoring would have starved the pump of oil, the crank would be running centrifugally on residual sludgetrap oil at best. It is hard to imagine that the shells wouldn't have suffered to some degree.
Or does " I blew an oil line" mean the return line disconnected? In which case we have an entirely different scenario.

Whatever, I think your measurements so far are on the low side of OK and warrant further investigation.

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It's going to be a while before I can get any hot motor info. Woke up to snow in town this morning and So. Cal. is under water. The oil line that blew was the supply to the rockers. It came off at the metal oil supply connection at the rockers. The metal line is chrome and very smooth. There was NO metal debris in any of the screens, the sump or the filter which is in the return line. The oil light used to flicker at idle after a hard uphill run on a hot day. I put two very thin brass washers behind the spring in the switch and have not seen a flicker since. I use Valvolene 20w50 4 stroke motocycle oil and have for years. Keep the questions and advice coming. It makes me think. Thanks.


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Thanks Desco,
As it was only the rocker pipe that came off, there is no reason to suspect any bottom end damage as a consequence.
It is unlikely there was any damage whatsoever.
So I would say that your oil pressure is somewhat suspect, but no more than before the incident. Trust the Triumph resilience in such matters and ride on!

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The tried and tested method to calibrate gauges is to send them away to someone who calibrates gauges, with an associated cost.

Probably possible to build a deadweight tester in the lock-up, should be accurate enough.

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This thread is a big deal about nothing..


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I hope so. There are places I ride in Nevada where I don't see any sign of other humans for an hour or more. I some times wonder what an old man like me, on a 40 year old Triumph is even doing here. I have to laugh when I think of some one finding a nice old Triumph parked beside the road with a pile of bones, bleaching in the sun, next to it.


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Could always fit one of them "tracker" things to the bike, at least that could be recovered wink

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