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Discussion Starter #1
I’d appreciate some views from more experienced owners on this. The oil pressure light has behaved this way since I’ve owned the bike some 2000 miles ago with no ill effects to date.

After a good run and with everything thoroughly warmed up I switch off the fuel when I get home and let the float bowls drain at idle. When the engine stops the oil light takes about 10 seconds to come on, this is with it having idled for a minute or so and it’s pretty consistent. On two occasions when I’ve been out and just stopped the hot engine using the kill switch the light has taken several minutes to illuminate, twice I’ve removed the headlight to see if a connector has parted but it hadn’t.

From a cold start it behaves more as I think it should, if I let the bike idle for a minute and then stop the engine the light takes about 4 seconds to come back on. I don’t do this often but wanted to check the difference between a hot and cold engine. The results are completely the opposite to what I’d expect and I'm sceptical about the indications when the engine's hot.
 

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A delay before the oil pressure light comes on after you stop the engine is normal on a Triumph twin, but it’s odd that it takes longer when hot. Maybe the sender switch is going funny.

If you have any worries about oil pressure, measure it with a gauge.
 

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Hi Rusty,

Most-likely ...

It Ain't Broke, Don't Fix It

:D

Oil pressure switches 'make' the warning lamp circuit at some feeble piffling pressure; I've posted several times on several old-Britbikes internet forums over the years that it isn't really an "oil pressure warning lamp" - if you see the lamp on when the engine's running, it's an "engine fcuked lamp" and "imminent bank balance demise warning lamp" ...

Otoh, even tickover pressure should be 20 psi on a twin according to the Triumph workshop manuals; that your bike's switch goes many seconds after you turn off the engine (stop the oil pump) before pressure falls to where it can 'make' the warning lamp circuit says your engine is most-likely good; as @Tritn Thrashr posted,if you're that worried, connect a gauge ... however, I'd add, be prepared to be surprised by what a gauge actually shows you about your bike's oil pressure ... :whistle

After a good run and with everything thoroughly warmed up
When the engine stops the oil light takes about 10 seconds to come on,
when I’ve
just stopped the hot engine using the kill switch the light has taken several minutes to illuminate,

From a cold start
if I let the bike idle for a minute and then stop the engine the light takes about 4 seconds to come back on.
The Triumph workshop manuals for the twins state "Idling" oil pressure should be at least 20 psi while "Normal running" is 60 psi; Les Williams defined "Normal running" as above 3,500 rpm in his oil pressure gauge kits' fitting instructions. So, if the engine's cold and you stop it only a minute after you started it, the oil pressure's never reached "Normal running"; all you're seeing is the cold oil pressure leaking out after you stop the engine/oil pump, 'til the pressure falls to where the switch can 'make' the warning lamp circuit.

Hth.

Regards,
 

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Discussion Starter #4
Thank you for the replies. I did have a theory that only once the crankshaft is fully warmed will the big end bearing clearances be optimal, that would take a good while to heat up.

I'll leave alone and stop thinking about it unless the pattern changes.
 

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I’d appreciate some views from more experienced owners on this. The oil pressure light has behaved this way since I’ve owned the bike some 2000 miles ago with no ill effects to date.

After a good run and with everything thoroughly warmed up I switch off the fuel when I get home and let the float bowls drain at idle. When the engine stops the oil light takes about 10 seconds to come on, this is with it having idled for a minute or so and it’s pretty consistent. On two occasions when I’ve been out and just stopped the hot engine using the kill switch the light has taken several minutes to illuminate, twice I’ve removed the headlight to see if a connector has parted but it hadn’t.

From a cold start it behaves more as I think it should, if I let the bike idle for a minute and then stop the engine the light takes about 4 seconds to come back on. I don’t do this often but wanted to check the difference between a hot and cold engine. The results are completely the opposite to what I’d expect and I'm sceptical about the indications when the engine's hot.
Hi Rusty,

Up to 10" is fine and normal. If I turn mine over with no HT using the kick starter and engine cold, the oil pressure light goes out immediately as the pump has pressurised the system, then about 10" later it comes back on, as the pressure in the system drops. If I do the same thing hot, the pressure drops faster, presumably because the oil is warmer and therefore thinner. Note; I have an uprated oil pump so the behaviour on our bikes may differ. However, what is odd in your scenarios are the occasions where the engine is hot but it takes several minutes for the light to illuminate. Surely the pressure has dropped well before that time and the light should have come back on? Of course I am assuming you were at idle when you hit the kill switch not at high revs with around 60psi in the system but even so, the pressure will drop off quite quickly, similarly to the other times you noted.

If I were in your shoes, I might suspect I have a sporadically sticky pressure switch. After all, these are generally just a spring operated contact and if there is a possibility that something causing the switch to stick OR it is just getting old and the spring is weak. I would be tempted to replace it. They are cheap enough and it is an easy job to do. I would want to be sure that if there was a real problem, that the oil light gave me some warning. After all, the moment you lose oil pressure the engine is not screwed: if you spot it early enough and shut the engine off you may be able to save an expensive repair bill. Additionally, most oil pressure switches are not "No Pressure" but are actually "Low Pressure warnings", so even with the oil light illuminated, if does not mean there is absolutely no oil flow (unless you have lost all your oil of course...). E.G. you can tickover for a few seconds with a failing pump without doing damage, however a few minutes running with a failing pressure switch not providing any warning is a different story.

Cheers,
Ian
 

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Hi Rusty, Ian,

pressure switch.
I would be tempted to replace it. They are cheap enough
Regrettably, this is a can of worms for the uninitiated and the unwary:-

. "cheap" is the operative word; ime, equals-piss-poor-quality has been a problem for at least a couple of decades.

. Triumph and BSA only ever used used two o.p. switch threads:-

.. 1/8"NPT ((American) National Pipe Tapered) only on early '69 triples and twins;

.. 1/8"NPS (National Pipe Straight) from part-way through '69 onwards - i.e. far-and-away the vast majority of bikes.

. However, there were originally three o.p. switch part numbers - D1943 (the one-and-only) 'T'apered-thread), D2133 (60-2133, including your bike) and 60-3719 ('74-on), so both the last two are/were originally 'Straight'-thread.

. Reasons why knowing the above is very important are:-

.. that couple of decades or so ago, some berk in the trade screwed-up royally - applied the D2133/60-2133 part number to the Tapered-thread switch; so, if you order using the part number in, say, a '72 T100 parts book, you'll be supplied a Tapered-thread switch instead of the originally-correct Straight-thread switch.

.. Ordinarily, that shouldn't be a problem as the maximum OD of both threads is the same (0.405"); the Tapered thread should then taper downwards (@ 6 degrees iirc). Regrettably, given much of the trade's apparent complete inability to QC anything, :bluduh Tapered-thread switches that start around 0.4" OD but taper upwards over the length of the thread have reached owners frequently.

.. Snag with particularly a twin's timing cover and an oversize Tapered thread switch owned by Big Spanner (in both senses of the word ...) is it takes very little effort to crack the timing cover around the switch ...

If you must change the o.p. switch, the Golden Rule is:-

A Switch Should Fit All The Way Into A Timing Cover Or Crankcase Turned Just By Thumb 'N' Forefinger.
If It Doesn't, Remove It And Fix Why It Doesn't,
Never Force The Switch With A Spanner (Wrench).​

However, even if a new switch does fit all the way into a timing cover or crankcase just with thumb 'n' forefinger, doesn't always mean it's the correct thread ... Every now-and-then, someone somewhere in the spares supply chain has a rush of blood to the head with the standard crap-quality switches and sources some from somewhere else. Unfortunately, they'll often source 1/8"BSP- or BSPT-thread switches - BSP is both one tpi different from NP (BSP 28 tpi vs. NP 27 tpi) and a smaller OD ... so the BSP switch thread'll fit in the NP-thread hole but, if the switch doesn't bugger the timing cover/crankcase thread when it's nipped-up, it'll piss oil when the engine's started because the threads don't seal on each other ...

Jeez ... you really couldn't make it up ... :gah

After all, the moment you lose oil pressure the engine is not screwed:
Ime, this is not a wise belief or hope.

Actually reading Triumph workshop manuals will show various switch 'trigger' pressures, but no higher than 7 psi; otoh, "Normal running" varies between 60 psi (C-range) and 85 psi (triples).

From first-hand experience, I can regrettably assure any reader that a triple's bottom and top ends are well-and-truly donald lo-on-ng before the standard switch deigns to illuminate the idiot lamp ... The 1985 fix total still makes me wince today ...

Posted experience on BritBike and here (most recently by @Truckedup?) suggests a twin's bottom end can escape - possibly because of the oil in the sludge tube? - if the rider's quick enough to switch off the engine; however, someone's still going to have to dismantle the engine to check ...

even with the oil light illuminated, if does not mean there is absolutely no oil flow
More experience or forum reading required. It can. A relatively-common occurrence on twins is inversion of Shonky-brand crankshaft/timing cover oil seals, meaning the input flow from the oil pump dumps straight into the bottom of the crankcase ... The recommendation is to check for and use only seals marked "Pioneer Weston" (sp?).

Given all the above, and the oil pressures even the Triumph workshop manuals say engines should operate with, the switch and idiot lamp are ime and mho A :wacko Idea - would any driver or rider with any real common sense be happy with a lamp that extinguished above, say, 10 mph instead of a speedometer? :goofy My T160's and T100 have long had permanent o.p. gauges, the T150 is checked regularly with a bolt-on gauge.

Hth.

Regards,
 

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Hi Rusty, have you tried removing the switch to see if it can be dismantled or simply cleaned out?

My money is on contaminants on the contacts or restricting internal movement. It might be that you can restore the original switch operation, ideally disassembling and cleaning it all properly. However, even if you cannot take it apart (and I suspect you cannot), a good soak in contact cleaner or flush out with MAF aerosol may well help. I guess in both cases you would have to push the ball in to get at the internals. It certainly would not hurt to try this.

Cheers,
Ian
 

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Discussion Starter #9
Hi Rusty, have you tried removing the switch to see if it can be dismantled or simply cleaned out?

My money is on contaminants on the contacts or restricting internal movement. It might be that you can restore the original switch operation, ideally disassembling and cleaning it all properly. However, even if you cannot take it apart (and I suspect you cannot), a good soak in contact cleaner or flush out with MAF aerosol may well help. I guess in both cases you would have to push the ball in to get at the internals. It certainly would not hurt to try this.

Cheers,
Ian
Thank you Boggie. I haven't tried either swapping or cleaning out the existing switch mainly because apart from the two occasions when the 'lamp of doom' stayed off for some minutes the pattern appears consistent. When the engine is cold it behaves as I would expect, when it's hot the lamp stays off for much longer and it's been like this since I've owned it (2.5k ago miles now). While the con-rods are still inside the crankcase I'm going to leave well alone and keep an eye out for any change in behaviour.
 

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No problem. In case you ever need it, here is the thread. However, there is no feedback to say how the cleaning went....
https://www.triumphtalk.com/threads/oil-pressure-switch.13411/

If you want to go new, assuming some of the posts above have not put you off trying.... About halfway down this page, you should find the correctly threaded new oil switch (at least that is what they say):
https://triumphbonneville.com/store/engi.html

Lastly: Don't be put off about scare stories about how much it costs to rebuild these engines: they are very simple and good quality replacement parts themselves are not expensive (you should see the parts alone cost I have for my 35 year old M635CSI engine rebuild). Of course if you get other people to build, rebuild and maintain your bike, it is a different story. Labour is not cheap but if you do it yourself, who charges for their hobby? It is all part of the fun....
?

Let us know how you get on. Good luck!
Ian
 

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Hi Ian, Rusty,

https://triumphbonneville.com/store/engi.html
About halfway down this page, you should find the correctly threaded new oil switch
60-3719A is widely-available. It's a replica of the original Smiths switch originally sold as plain old 60-3719, the latter number having been appropriated by the supplier of the variable-quality pattern Straight-thread switch https://www.google.com/search?q=triumph+60-3719&tbm=isch&source=univ&client=avast&sa=X&ved=2ahUKEwiGpvuT6JDkAhUxtHEKHeOGAqsQsAR6BAgJEAE&biw=1366&bih=625.

Hth.

Regards,
 

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Hi all,

I would only recommend buying pattern parts from trusted suppliers. I have found that Shropshire Classic Motorcycles to be reliable suppliers of quality parts. Hence the link I provided above.

Random Google or EBay searches can get you into a world of pain. I speak from personal experience. The amount of poor quality replica and counterfeit parts flooding the classic vehicle component market from the far east is epidemic.

Cheers
Ian
 

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My opinion is if you have money into the engine and care about, the pressure light is inadequate no matter what and an actual pressure gauge is required...The gauge may be unsightly for you originality guys, but engine problems from inadequate oil pressure is uglier...
 

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My opinion is if you have money into the engine and care about, the pressure light is inadequate no matter what and an actual pressure gauge is required...The gauge may be unsightly for you originality guys, but engine problems from inadequate oil pressure is uglier...
Spot on. ?
What are the chances of noticing an oil pressure failure whilst riding? The warning light is very hard to see, especially in bright daylight. It does give confidence before you ride out I guess.

Absolutely agree with regarding the gauge. L.P. Wiliams do a great gauge and pod that is sympathetic to the style of classic Triumphs:
https://www.triumph-spares.co.uk/oil-pressure-gauge-kit-leg-0002
However, I am looking at the potential of fitting a pressure gauge into the top/rear of the headlamp bowl, rather like the older bike ammeter fitment. Available internal space and ability to accurately/neatly cut a 2" hole are thenlimitimg factors. I have a set of sheet metal hole cutters in the workshop but they will not work on compound curves. I could of course use the older shell but I don't want to end up with blanked off warning light holes.

For now I might fit a loud 12v buzzer across the warning light feed. I bought a set of 5 from R.S. a few years ago and used one in my Lotus Seven and another in my S2 Land Rover. They are very loud and an audible warning is in some ways better than even a gauge; you cannot turn your ears off. However, I wonder if I would hear the buzzer in my Seven, with no roof and its 4:2:1 exhaust exiting by my right ear. My Bonnie would be challenging too; helmet on, 1.5" headers and straight through Norton pea shooters...

Cheers,
Ian
 

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Hi Ian,

I would only recommend buying pattern parts from trusted suppliers.
Random Google or EBay searches can get you into a world of pain. I speak from personal experience. The amount of poor quality replica and counterfeit parts flooding the classic vehicle component market from the far east is epidemic.
'Fraid you misunderstand the situation as far spares for our old heaps are concerned.

Hinckley owns all the rights associated with the "Triumph" name. Midlands multi-millionaire house-builder John Bloor bought the rights in 1984 at the liquidation auction of the Meriden Co-operative. It was then his millions that paid to design and develop the 1990's Triumphs, build the Hinckley works and otherwise support 'new Triumph' 'til it turned a profit.

Hinckley does not have anything to do with 'old Triumphs' apart from taking the royalty cheques from anyone who sets up to make or sell parts for our old heaps and ad hoc plundering of the history to flog 'new Triumphs'. Hinckley does not do anything to ensure any quality or accuracy in anyone's spares for our old heaps.

The vast majority of spares for our old heaps are made or commissioned by one of a handful of wholesalers, almost all based in GB. You've probably seen L.F. Harris mentioned in the Forum; "Velocette" is another - the name's in quotes because it's one of a number of more-obscure British marque names acquired by a guy called Matt Holder in the 1970's and 1980's. Aside, if not still there, Holder's company was originally based in the Meriden No.2 factory, across the road from the No.1 factory in all the 1970's sit-in pictures. Tri-Cor England aka Andy Gregory and Wassell are pretty-much the others. Emgo is a spares supplier better-known in the US; aiui, they don't wholesale to British retailers while Wassell doesn't wholesale to US retailers ...

In the original context of this thread, all the oil pressure switches (originally made by Smiths, as in original speedos. 'n' tachos.) are made or commissioned by one of those wholesalers. As such, whatever's sold by Shropshire Classic Motorcycles is exactly the same as any other retailer that cares to order the part from the wholesaler; the only difference between the vast majority of retailers is the amount of care put into QC'ing parts they receive before retailing 'em and how quickly mistakes are resolved.

The above doesn't include Lucas or Amal parts:-

. As I believe I've posted for you before, the 'original Lucas' that made the electrics on our old heaps was bought by a company called TRW in 1979. For years afterwards, TRW weren't at all concerned by the number of people making crap knock-offs of 'original Lucas' automotive parts. However, in 2014, TRW licensed the "Lucas" automotive rights to Wassell, who'd been one of makers of crap knock-offs for several decades. Wassell have since expended most financial effort stopping any other parts maker - irrespective of quality - using any "Lucas" branding; the 'handy' upshot of that now is, if you see an electrical part in new-looking green-'n'-white "Lucas" packaging and/or marketed under the "Genuine Lucas" banner, you can assume it'll likely be crap because it's by Wassell. :rofl

. Not sure who owns the Amal rights as whoever's made them in certainly the last half-century or so has been a licencee. Original Amal bits on bikes owned by most of Forum contributors were made by IMI - Imperial Metal Industries. The current licencee is Burlen Fuel Systems; regrettably, Burlen don't have the financial muscle of either Hinckley or Wassell to prevent counterfeit parts so are most afflicted; if you don't buy direct from Amal/Burlen, be very careful from whom you do buy.

Hth.

Regards,
 

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Hi again Ian,

My T160's and T100 have long had permanent o.p. gauges, the T150 is checked regularly with a bolt-on gauge.

Absolutely agree with regarding the gauge. L.P. Wiliams do a great gauge and pod that is sympathetic to the style of classic Triumphs:
https://www.triumph-spares.co.uk/oil-pressure-gauge-kit-leg-0002
Not sure what you mean by "sympathetic to the style of classic Triumphs" as that particular "pod" fits only T160's (I've one on each of mine) and '79-on twins with the T160's idiot-lamps-'n'-ignition-switch box between the speedo,-'n'-tacho. mountings.

Reason is the moulding in the picture around the gauge itself is L-shaped in cross-section, the vertical part mounts everything on a longer version of the screw that secures the front of the idiot-lamps-'n'-ignition-switch panel to the box. The two screws in the picture simply secure the front cover moulding to the gauge mounting - the thick semi-circular line in the picture is a piece of trim over the top edge of the front cover moulding.

Background
L.P. Williams was founded by the eponymous Les originally as a triples specialist. Les had worked for Triumph since his National Service in the 1950's and in Meriden's Experimental Department before the heyday of the racing triples in the early 1970's. However, what embedded him in the triples' and Triumph history was he took one of the three production-racing triples - Slippery Sam, now in the National Motorcycle Museum - that'd already won the 1971 Production TT, primarily to five more consecutive Production TT wins but also to other racing successes, either with just a nod-and-a-wink from the factory or as a privateer, with very little sponsorship.

Having been made redundant both by BSA in 1973 and NVT in 1976, Les originally set up in his garage at home. However, even in the late 1970's, there were enough triple enthusiasts willing to pay for his experience to convince him to set up LPW with two of this Experimental Department colleagues - Arthur Jakeman and Harry Woolridge - in proper commercial premises.

Alongside work on standard triples, Les also made "Slippery Sam Replicas":-



... original bases were T160's sold by NVT to Saudi Arabia in 1975, these were usually in a bad state - damaged and/or missing major parts - however, they were consequently cheap enough to be completely rebuilt and fitted with special Sam parts (tank, seat, etc.) for a not-exorbitant retail price and profit.

However, as Les's fame spread, he soon found himself receiving 'phone calls that started, "I've bought a Slippery Sam Replica and it's a heap of sh..."; he discovered that his mistake had been also to sell the SSR parts separately, people were cashing-in dressing-up standard triples with the bits but without the specialist rebuilds by Les, Arthur and Harry. :(

So they developed the Legend:-



... still based on a T160 but more a long-distance sports-tourer - the SSR/Legend tank holds over five Imperial gallons so, if you want to cover 500 miles (two tankfuls) or more in a day, still walk normally at the end of it and repeat the following day, things like the Legend's seat and riding position are essential too.

This time around, Les didn't sell the major parts - tank, seat, etc. - separately; however, he did sell smaller parts like the "[oil pressure] gauge and pod", that's the reason your link still has a part number beginning "LEG".

Aside: from the late 1980's 'til Les, Arthur and Harry retired in 1993 (and sold LPW to Trevor Gleadall), as the Saudi T160's dried up, they also produced the Buccaneer:-



... similar to the Legend but based on '79-on T140's. Note they were also fitted with the "[oil pressure] gauge and pod"; nevertheless, the connection to a twin's engine is completely different from that to a triple's engine; anyone considering the current linked "gauge and pod" for a '79-on twin should check whether it can come with twin-specific engine connection parts.

potential of fitting a pressure gauge into the top/rear of the headlamp bowl, rather like the older bike ammeter fitment.
Gauge at the "rear of the headlamp bowl" would be under the idiot-lamps-'n'-ignition-switch box on your bike.

Further forward in the headlamp shell? Not having tried it myself, I couldn't say if it's impossible but:-

. My T100 having an Ammeter in the headlamp shell and knowing the overall height of more than one o.p. gauge and their protuberances, imho at best it's likely to be a lot of pain for not a lot of gain.

. Ime, cutting a hole in a compound-curve headlamp shell is easy with the right kit, so I can't see that Les Williams would've gone to the expense of moulds for the "pod" pieces if putting the gauge in the headlamp shell was easy?

... Consider a mock-up with an off-the-shelf 2"/50 mm. gauge and pre-'71 7" headlamp shell plus off-your-bike headlamp and rim? Any parts not required subsequently can go on the 'Bay?

loud 12v buzzer across the warning light feed.
Bear in mind that'll sound any time the ignition's switched on but the engine's not running ... might test swmbo's/neighbours' patience if you want to go out for a 6-am-Sunday-morning blast?

wonder if I would hear the buzzer
Another bike I own in a US-model Honda, fitted with an indicators buzzer. I don't have any trouble hearing it on the motorway when indicating a lane-change or turn-off, but it isn't deafening when indicating a turn at town speeds (does stop some peddies stepping out in front of the bike while looking anywhere but at approaching vehicles :cool:).

Hth.

Regards,
 

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Hi Boggie,
I do think that a gauge is a highly desirable asset, way beyond the lamp or buzzer. Even the pre-units had a gauge of sorts, the indicator button that extended proportionally to oil pressure.

On your thoughts about mounting an oil pressure gauge in the headlamp shell, apart from the fiddly job of cutting the hole, I think there are a few other aspects to consider.

The depth (penetration) of the gauge into the shell is severely limited by the reflector.
Also, capillary gauges have a fairly stiff tube which needs a fairly straight run to the connection on the bottom of the gauge. And that connection is usually on the end of a substantial spigot, which is in addition to the main body depth of the gauge.
Whether the connection is central or not will be important too.

Making a sleeve/collar to fit between the bezel of the gauge, to the curve of the shell, will be a fussy job.

If Stuart could inform of the LPW gauge dimensions and details mentioned above, that could inform you of the feasibilty of using that gauge (though to my mind, it is a very expensive OPG.

There are many OPG's available, mainly of 52mm dia. There are even some electronic ones such as:
https://www.altecautomotive.co.uk/durite-52mm-oil-pressure-gauge--brelectrical-sender-unitbr12-voltbr-alt0-523-17-2686-p.asp
which will eliminate the spigot/pipe connection issue. The sender thread should suit the cover thread, though as its tapered into a parallel hole, it may need some PTFE tape. It would still be sensible to check with the vendor regarding the depth of the gauge body, and that it works with your ground polarity.
 

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Hi Chris, agreed on all your points. Even if I can get a hole-cutter to create a neat 52mm diameter hole in the compound curve of my headlight bowl (not seen a tool capable of doing this), the interface between the hole and gauge would be unlikely to meet any decent standard, let alone the chance of finding a gauge shallow enough to fit the space.

The LP Wiliams oil pressure gauge will perfectly fit my 79 T140e but I rather like seeing the big chrome headlamp between the clocks and I want to keep the bike as standard as possible. Also the LP William's branding rather spoils the look too. It would be great to fit a matching chrome-rimmed Veglia oil pressure gauge but they are no longer made. Perhaps fit a Smith's gauge instead?

I am still in favour of my 12.6v Zenner diode idea. ZD feeding the +ve side of the buzzer and the other side to the oil pressure switch. I suspect that a loud buzzer is a better warning than a gauge out of eyeline and using a 12.6v (or maybe slightly higher) zenner will mean that the buzzer only sounds when the the engine is running and there is low oil pressure as it only gets power above that voltage. I.e.when the alternator and therefore engine are running.

Additionally, I can use the zenner to power my hidden super-bright DRL LED. ZD connected to LED +ve side with pilot light +ve on the LED -ve side. This means that when running with no lights in daytime, the DRL will be on but as soon as I switch the lights on, it goes out.

Simple stuff I know but I feel that both the buzzer and DRL would be sensible enhancements without changing the bikes look in any way. Oh, and all this for about a tenner and an hour of spare time.

Cheers,
Ian
 

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Hi Chris, Ian,

If Stuart could inform of the LPW gauge dimensions
If the current gauge is the same as the ones I have, it's standard 2" or 50 mm. diameter and is ~3" below the bezel.

capillary gauges have a fairly stiff tube
LPW have always supplied a flexible plastic capillary tube, the gauge and engine fittings are the stiffest parts.

which needs a fairly straight run to the connection on the bottom of the gauge.
When Les developed the "pod" for T160 mounting, he allowed for a "straight run" between the pipe connection and the gauge. However, something like the gauge in the Triples Rule 3 Gauge Bracket has a specially-made solid fitting that attaches to the gauge male thread and has another male thread at ~120 degrees for attaching the flexible capillary tube.

mounting an oil pressure gauge in the headlamp shell,
The depth (penetration) of the gauge into the shell is severely limited by the reflector.
A starting point would be to measure the depth of a standard pre-'71 Ammeter - original or pattern.

Making a sleeve/collar to fit between the bezel of the gauge, to the curve of the shell, will be a fussy job.
"a sleeve/collar" would only be required if the gauge had to protrude above the shell; otherwise pre-'71 Ammeters are standard 2" diameter and the underside of its bezel only required/s a rubber washer to seal on corresponding headlamp shells, later bikes - e.g. '79 T140 - have the same basic shell.

it is a very expensive OPG.
The price of the LPW kit is a combination of the high price of small quantities of high-quality fibreglass mouldings and high-quality gauge.

There are many OPG's available,
But not so many quality ones ...

Les originally used Smiths gauges. However, after Smiths itself stopped making automotive instruments, the business was taken over by Speedograph Richfield. Regrettably, the quality gradually declined and it was Les that stopped using them in the 1980's. :(

Similarly, my T100 has one of the aforementioned Triples Rule 3-gauge brackets. When I bought it, the importer was bringing in just the brackets, fitting them with a GB-sourced OPG. When I first started my T100, an inadvisable twitch of the throttle and cold oil shot the pressure past 100 psi ... where the needle stuck. I contacted the gauge maker and was advised that an exact replacement would be about £10 ...

Note the LPW gauge only goes up to 100 psi. With cold oil, the better triple oil pump can exceed that without breaking sweat. Absent a gauge that could read up to, say, 120 psi, a good-quality gauge is essential.

electronic [OPG]
check with the vendor
it works with your ground polarity.
"ground" isn't a problem as long as neither gauge nor sender "ground" through their mountings; if both have -ve and +ve wires, they're just connected to the corresponding battery terminals, one or other through switches and the bike's wiring.

The problem with anything particularly on one of these old boneshakers is vibration. No-one makes an electronic OPG that puts up with the vibes on these old heaps, so whoever does the mounting has to allow for that. Given what started this thread was concern about whether a simple pressure switch was working correctly or not, testing an electronic sender and gauge to ensure they're both working correctly over a range is an order of magnitude more difficult. Otoh, if you suspect a mechanical gauge, you just connect another one.

Even if I can get a hole-cutter to create a neat 52mm diameter hole in the compound curve of my headlight bowl (not seen a tool capable of doing this),
Shortly before moving to Scotland, I had two more wiring holes cut in my T100's headlamp shell (has only one as standard). The guy I used for specials was a toolmaker at a local engineering company; as well as having his own well-equipped home workshop, he was allowed to slip in 'private' jobs at work. I don't have any idea whether he used "a hole-cutter" but, given the shell came back with the two extra holes as required and without any problems, as I say, clearly such a job isn't a problem for anyone "with the right kit", whatever it might be.

the interface between the hole and gauge would be unlikely to meet any decent standard,
As above, a '79 T140's headlamp shell isn't basically any different from a pre-'71 shell with a hole for an Ammeter. Similarly, the Ammeters were/are nominal 2" diameter. Given pre-'71 Britbike headlamps have never routinely leaked through "the interface between the hole and gauge" (nor through the idiot lamp and switch holes that've been in more headlamp shells for longer), any concern is imaginary.

Hth.

Regards,
 
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