Oil pressure, or temperature gauge for R 75/5

2wheeljunkie · Jan 13, 2022

When I got my 1972 R 75/5, a friend, who had owned a number of BMW bikes, told me that I should install a gauge to monitor my oil, as the "idiot light" should not be relied on. I can't remember if this was a pressure gauge, or a temperature gauge. He installed it for me and I don't recall that it was a complicated thing to do, but I can't recall what was done. As well, I cannot remember whether it was a pressure, or a temperature gauge. I seem to think it was a temp gauge as I remember thinking that... lower temp reading meant higher pressure, and higher temp meant lower oil pressure, and....if the temp suddenly soared... it meant trouble.

Sorry to be a bit vague and confused, but this was 50 years ago.... and, although I remember a lot about the rides I had on that bike, I don't recall a lot about the service aspects.

I would like to install a gauge on my current 1972 /5 so I appreciate anyone's advice. I did a few internet searches and found a few comments, but nothing that really gave me the info I am looking for.

20774 · Jan 13, 2022

I think the general consensus I've seen on either oil pressure or temp gauges is to not try and over complicate the system. Especially with an oil pressure gauge as you add another failure point in the system. As for temperature, most have considered using the dipstick which has a temperature readout on the end. It's not really usable to read while riding down the road as you have to seriously take your eyes off the road to look down at it. But I suppose it could be useful in traffic when stopped at a light.

As this is something that few have ever done in terms of oil pressure, I'm not sure where to go for guidance. I checked Matt Parkhouse's articles and he's never mentioned an oil pressure gauge setup.

dennisdarrow · Jan 13, 2022

For me, even with a gloved hand, leaning over and touching the valve cover surely does give me an immediate feedback. The idiot light oil pressure "guage" is a good one. If, anytime it comes on after starting the engine, idle/4K/ or cruising, PULL THE CLUTCH, KILL THE ENGINE, AND GET THE MACHINE STOPPED. Of course use your common sense in traffic; but do get that engine stopped ASAP. Don't complicate the simple............Dennis

nickrides · Jan 13, 2022

VDO Gauges are good, rugged and reliable, don't think they are waterproof thou, but I don't know.
They were standard aftermarket equip in my VW days
We always had Oil pressure, Temp and Cyl, head temp gauges.

Search VDO Gauges in google.

Nick
1978 R80/7

melville · Jan 14, 2022

I got an oil temp dipstick with my /7:

I can't say it's the most useful thing. Hard to read while riding. Perhaps if I put a red stripe on the dial around 275.

stevenrankin · Jan 15, 2022

long ago

When I bought my first brand new airhead, I asked my dealer/mechanic, about adding oil pressure and temperature gauges or perhaps substituting the installed Clock, Voltmeter (This was an RT). His advice was not to bother with either. According to him, unless I am constantly riding in the desert in extreme high temperatures, a temperature gauge is pretty much for show. IF for the rare happenstance of being caught in traffic or some such thing, even with a temperature gauge, unless the bike is allowed to have air circulation, damage could be done. Long term idling is not recommended. Anyway, a temperature gauge wouldn't do much in extreme situations except to cause worry and if in that extreme a situation, worry should already be there.

As for the oil pressure gauge, he made sense when he said the idiot light system is very good, and works very well, giving much faster notice of low pressure than would a gauge. His thinking is that by the time a rider noticed the drop in pressure on a gauge the damage could be well done. The idiot light was faster and more noticeable. There was no sense in having two systems, one of questionable value and one of solid value. After all, these are not airplanes where a real sense of oil pressure may mean flying to a safe place or crashing. His advice was simple, if the oil pressure light comes on, Stop and shut the bike off immediately. That meant not only a steady light but a flickering light as well. It was certain the light had a better chance of alerting the rider to oil pressure issues faster than the gauge.

So, he did say keep the voltmeter as it gives a good idea as to the overall charging system health but again, pay attention to the light. The most important item on the dash aside from speedometer was in his mind the clock. The clock would keep me out of trouble with the girlfriend at the time by keeping me on the toes for date times, or with the boss for keeping on time for work.

All the years and miles I have been riding, I have never found an issue with his words then. In my cars with oil pressure and temperature gauges, I rarely look at them. While I have never had a low oil pressure or overheat light come on, I have had tire pressure warning come on and it has always been faster than the telltale signs of a flat tire in the steering wheel. Okay not the same thing but the point is, the light is faster than the feel, or scanning.

Yes, I did take flying lessons long ago and did learn to scan the gauges. In the air, there was less to concentrate on and taking my eyes from the sky to the gauges was not as big a deal as taking my eyes off the road where some body is possibly ready to kill me.

A long winded reply, sorry, I am snowed in, not riding and. bored this Saturday morning. Hope all of you who can ride are doing that. St.

2wheeljunkie · Jan 17, 2022

STEVENRANKIN said:
When I bought my first brand new airhead, I asked my dealer/mechanic, about adding oil pressure and temperature gauges or perhaps substituting the installed Clock, Voltmeter (This was an RT). His advice was not to bother with either. According to him, unless I am constantly riding in the desert in extreme high temperatures, a temperature gauge is pretty much for show. IF for the rare happenstance of being caught in traffic or some such thing, even with a temperature gauge, unless the bike is allowed to have air circulation, damage could be done. Long term idling is not recommended. Anyway, a temperature gauge wouldn't do much in extreme situations except to cause worry and if in that extreme a situation, worry should already be there.

As for the oil pressure gauge, he made sense when he said the idiot light system is very good, and works very well, giving much faster notice of low pressure than would a gauge. His thinking is that by the time a rider noticed the drop in pressure on a gauge the damage could be well done. The idiot light was faster and more noticeable. There was no sense in having two systems, one of questionable value and one of solid value. After all, these are not airplanes where a real sense of oil pressure may mean flying to a safe place or crashing. His advice was simple, if the oil pressure light comes on, Stop and shut the bike off immediately. That meant not only a steady light but a flickering light as well. It was certain the light had a better chance of alerting the rider to oil pressure issues faster than the gauge.

So, he did say keep the voltmeter as it gives a good idea as to the overall charging system health but again, pay attention to the light. The most important item on the dash aside from speedometer was in his mind the clock. The clock would keep me out of trouble with the girlfriend at the time by keeping me on the toes for date times, or with the boss for keeping on time for work.

All the years and miles I have been riding, I have never found an issue with his words then. In my cars with oil pressure and temperature gauges, I rarely look at them. While I have never had a low oil pressure or overheat light come on, I have had tire pressure warning come on and it has always been faster than the telltale signs of a flat tire in the steering wheel. Okay not the same thing but the point is, the light is faster than the feel, or scanning.

Yes, I did take flying lessons long ago and did learn to scan the gauges. In the air, there was less to concentrate on and taking my eyes from the sky to the gauges was not as big a deal as taking my eyes off the road where some body is possibly ready to kill me.

A long winded reply, sorry, I am snowed in, not riding and. bored this Saturday morning. Hope all of you who can ride are doing that. St.

Thanks for the reply, mostly all good points, although I don't quite agree with some of the advice you were given, but everyone is entitled to their own thoughts and opinions. Opinions of service mechanics are as varied as the number of dealerships in the country, and getting another opinion is as easy as going to another dealer.

I personally don't think that the "idiot light" system on a 50 year old motorbike is something that I would rely on for letting me know if I had an oil issue. Those sensors weren't all that reliable 50 years ago, and I'm not sure that 50 years of use has improved them any. As well, I am not sure that this light sensor is quicker than a constant readout from a gauge. The stock sensor on those /5 bikes was set to signal at 3-8 psi, and generally speaking, the oil pressure will not drop below 15-18 psi, even with very hot and thin oil, unless the engine is very worn (according to "Snowbum's BMW Motorcycle Repair & Information Website"). Waiting until the oil pressure gets below 3-8 psi, to signal that sensor is not very fast, even if the sensor still works. Being able to read a gauge that gives variable readings depending on outside air temperature, length and distance the bike has been running, how hard it has been ridden, driving habits, driving conditions, i.e...stop and start in town, open highway, etc., etc. always gave me (on my original '72 bike) a good idea of the condition of the oil lubing the engine. I never had to take my eyes off the road to see the gauge, it was mounted near the center of the handle bars and it was no different seeing the gauge than it was seeing the speedometer, the tach, or even the "idiot light". And it was definitely nowhere near the amount of time that my eyes might leave the road to see all the computer generated readouts on my 2014 RT. I am a firm believer in keeping my eyes aware of everything going on around me...cars waiting until I am close enough so they can pull out in front of me...an animal lurking on the side of the road, waiting to challenge my brakes.....bumps, potholes, a pile of rubber from a transport tire,... etc., etc. I am not advocating looking at all these readouts and/or gauges, but I do check my speed occasionally, and looking at a gauge in the same location would not be a distraction.

I also flew for a time...ultralight aircraft, and small, single engine aircraft. I also made over 1600 skydives, where I had to glance at an altimeter occasionally in freefall, and under canopy to judge my set up for landings. I depended on the readings that I saw, which were done with a very quick look, especially the ones in freefall. I know that a flashing light might bring one's attention to a problem quicker than a gauge, but that is only good if there is a real problem, i.e., oil pressure below 3-8 psi. Glancing at a gauge where I get a constant read on what the oil pressure is all the time, might warn me sooner if oil psi started dropping...maybe a faulty gasket, seal, etc. and give me time to pull over and see what is going on. Getting a flashing yellow light when the oil pressure is so low it has probably done serious damage already doesn't really help me. I just don't feel that anyone would have to take their eyes off the road to look at a gauge that is correctly positioned for easy viewing. I recall the one that I used back in the 70's and I know it gave me a lot more information and confidence than that light which was designed to wait until the oil pressure was so low that it was almost non-existent.

Sorry for the lengthy reflections on your thoughts (it is snowing here right now as well, and no biking for at least 3 more months). Thanks for your thoughts, I appreciate your insight as it is all a learning process and varying opinions will give more insight into things. I am now in the process of digging up a number of old slides of my R 75/5 which I haven't looked at for 30-40 years and hoping to find a picture of the gauge I had on that bike. Had a lot of pictures of it on a trip through the Rockies. It snowed on that trip as well, woke up with 6 inches of snow on the tent and had to wait until the snow melted on the highway before proceeding. No danger of the oil overheating on that trip.

20774 · Jan 17, 2022

Sounds like you have some background in these kinds of notices/gauges so you should have no problem moving forward. It is afterall your bike and you can do what you want! About the only you haven't addressed, and it might be on the minor end of things, is that you might be introducing new failure points. But if you include things in your checklist and are aware of those issues, you should be all set.

Good luck! Let us know how it comes out.

gregfeeler · Jan 18, 2022

erictucker123 said:
Thanks for the reply, mostly all good points, although I don't quite agree with some of the advice you were given, but everyone is entitled to their own thoughts and opinions. Opinions of service mechanics are as varied as the number of dealerships in the country, and getting another opinion is as easy as going to another dealer.

I personally don't think that the "idiot light" system on a 50 year old motorbike is something that I would rely on for letting me know if I had an oil issue. Those sensors weren't all that reliable 50 years ago, and I'm not sure that 50 years of use has improved them any. As well, I am not sure that this light sensor is quicker than a constant readout from a gauge. The stock sensor on those /5 bikes was set to signal at 3-8 psi, and generally speaking, the oil pressure will not drop below 15-18 psi, even with very hot and thin oil, unless the engine is very worn (according to "Snowbum's BMW Motorcycle Repair & Information Website"). Waiting until the oil pressure gets below 3-8 psi, to signal that sensor is not very fast, even if the sensor still works. Being able to read a gauge that gives variable readings depending on outside air temperature, length and distance the bike has been running, how hard it has been ridden, driving habits, driving conditions, i.e...stop and start in town, open highway, etc., etc. always gave me (on my original '72 bike) a good idea of the condition of the oil lubing the engine. I never had to take my eyes off the road to see the gauge, it was mounted near the center of the handle bars and it was no different seeing the gauge than it was seeing the speedometer, the tach, or even the "idiot light". And it was definitely nowhere near the amount of time that my eyes might leave the road to see all the computer generated readouts on my 2014 RT. I am a firm believer in keeping my eyes aware of everything going on around me...cars waiting until I am close enough so they can pull out in front of me...an animal lurking on the side of the road, waiting to challenge my brakes.....bumps, potholes, a pile of rubber from a transport tire,... etc., etc. I am not advocating looking at all these readouts and/or gauges, but I do check my speed occasionally, and looking at a gauge in the same location would not be a distraction.

I also flew for a time...ultralight aircraft, and small, single engine aircraft. I also made over 1600 skydives, where I had to glance at an altimeter occasionally in freefall, and under canopy to judge my set up for landings. I depended on the readings that I saw, which were done with a very quick look, especially the ones in freefall. I know that a flashing light might bring one's attention to a problem quicker than a gauge, but that is only good if there is a real problem, i.e., oil pressure below 3-8 psi. Glancing at a gauge where I get a constant read on what the oil pressure is all the time, might warn me sooner if oil psi started dropping...maybe a faulty gasket, seal, etc. and give me time to pull over and see what is going on. Getting a flashing yellow light when the oil pressure is so low it has probably done serious damage already doesn't really help me. I just don't feel that anyone would have to take their eyes off the road to look at a gauge that is correctly positioned for easy viewing. I recall the one that I used back in the 70's and I know it gave me a lot more information and confidence than that light which was designed to wait until the oil pressure was so low that it was almost non-existent.

Sorry for the lengthy reflections on your thoughts (it is snowing here right now as well, and no biking for at least 3 more months). Thanks for your thoughts, I appreciate your insight as it is all a learning process and varying opinions will give more insight into things. I am now in the process of digging up a number of old slides of my R 75/5 which I haven't looked at for 30-40 years and hoping to find a picture of the gauge I had on that bike. Had a lot of pictures of it on a trip through the Rockies. It snowed on that trip as well, woke up with 6 inches of snow on the tent and had to wait until the snow melted on the highway before proceeding. No danger of the oil overheating on that trip.

I was selling new BMWs in the 1970's and I never saw a case of an unreliable oil pressure sensor. Do you have any proof that they are unreliable. They are easy to replace if one is concerned about the age of the sensor. I think the larger question is what could cause low oil pressure on these engines? Where's the fire?

On some models you can screw up the oil filter change by not using the correct O-rings, but that should be indicated by the pressure light at first start up. The oil pickup tube could come un-bolted, but that would cause instant loss of oil pressure, and the light would again show this. You could hit something and put a hole in the oil pan, but I'm thinking you would have noticed such and impact, and again this would cause complete loss of oil pressure. Engine wear - as you cited from Snowbum - is almost never going to be so bad as to cause a critical drop in running pressure. In my experience the oil pressure lights go out almost instantly as the engine starts.

Perhaps I've missed something, but in 50 years of experience with these engines, I've never see one lunched due to chronic low pressure which wasn't indicated by the oil pressure light. If I'm missing something I would like to know.

pglaves · Jan 18, 2022

GREGFEELER said:
Perhaps I've missed something, but in 50 years of experience with these engines, I've never see one lunched due to chronic low pressure which wasn't indicated by the oil pressure light. If I'm missing something I would like to know.

Greg, What you are missing is that we have become a data driven society. Witness the new TFT and Wonderwheel. What is a poor Airhead to do lacking information and data? I think somebody needs to devise a set of sensors; oil temp, exhaust gas temp, oil pressure, exhaust mixture, etc. and integrate it all into a smart phone screen using a bluetooth app. :whistle

gregfeeler · Jan 18, 2022

PGlaves said:
Greg, What you are missing is that we have become a data driven society. Witness the new TFT and Wonderwheel. What is a poor Airhead to do lacking information and data? I think somebody needs to devise a set of sensors; oil temp, exhaust gas temp, oil pressure, exhaust mixture, etc. and integrate it all into a smart phone screen using a bluetooth app.

Doh!!

What the hell was I thinking!! Naturally, you are spot on. I'm going back into lurking mode now to watch for what I should be doing to my R75/5 as I revive to ride to the Springfield MOA Rally in June. Thanks for the spiritual guidance.

20774 · Jan 18, 2022

How many cars/trucks these days have oil pressure readings on a gauge? Seems like every vehicle has idiot lights. :dunno

stevenrankin · Jan 18, 2022

50 years

Yeah, I have 50 years of riding, 37 years with one bike. Greg, you are spot on, the oil light will light asap if there is a problem with the stupid rings on the 77 and newer airheads. I will admit, I have in many filter changes made a mistake of not getting things back together 100%. The light is a heck of a lot easier to see while the bike is on the lift than looking at a gauge. And it is surprising the light comes on faster than the oil leak happens sometimes!

As for flying and skydiving, I admit there is wisdom in keeping an eye on dials, I even said that when I was taking flying lessons I was told this. Yes, I think I would keep an eye on the altimeter skydiving just in case the automatic (if there is such a thing) chute system decided to take a break.

Oh well, like Paul says, information and more is wanted. I guess if the fellow wants to complicate things it is his money and bike, I am just a jerk for questioning the need for a gauge when the light works fine or better. Then again, I am still riding without bluetooth music in my hemet or GPS. I am not a member of the Airhead club but their motto makes sense to me. St.

6322 · Jan 18, 2022

I’ve had a couple of oil sending units on BMWs fail over the years. Not, not sending a signal to the indicator light, but becoming a source of an oil leak. This usually manifested itself first as oil on my boot but occasionally emptying the oil from the engine under pressure. The lights never failed to light though. Good luck with your project. Let us know how it comes together.

lkchris · Jan 22, 2022

Auxiliary gauge panels were popular in the day ... fueled by none too accurate hype from the aftermarket. Sort of an ego thing ... by buying their product you show you know more than the design engineers. The #1 requirement for these "mods" is that they be visible ... so others can easily see your genius.

Oil pressure, or temperature gauge for R 75/5

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