R100rs engine 1984 oil pressure sender

Sender original from engine has the larger spigot, coarser threads as well the other two are from vw bugs that are supposed to fit ? of course they're too small .....is my sender original?

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Snowbum mentions that the earlier Airhead switches were NPT 3/8" threads (pipe taper thread) and the specs say the threads per inch are 18 and outside thread diameter is 0.675 inches. But for the 1984 model, the switch should be M12 x 1.5 or 12mm outside diameter and 1.5mm per thread. I can't imagine that the coarser switch is standard. Is it possible that the engine isn't a 1984 (unlikely) or that someone in the past had to tap this hole to accept the NPT threads.

Here's a post about substitutes:

https://ibmwr.org/original/otech/partsubs.shtml#Airheadoilp

The mid seventies car switch and some VW switches probably work. But the price of a new one is relatively cheap from BMW.

Still, I don't understand why your block has the coarser threads.

Here is my engine number I have no idea the age of this engine it's in a different frame but I was told it's a 1984 r100rs but it could be an 83 year-old or ....

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That engine number equates to a 1982 R100RT built February 1982. But a few things trouble me...maybe someone with a bike from this period can chime in. I don't see the roundel...maybe it's on the far right and just cut off from the picture. Second, it's my understanding that the numbers should be stamped into the engine case. Unless I'm seeing it wrong, those numbers appear to be raised. Strange also that the numbers encroach on the area where the dipstick seats on. Makes me kinda wonder about things. It would be good to see more of this engine.

Back to the original situation. If the sender you took out definitely has the coarser threads, then it would appear you need to go back with a similar one. Given what I offered per Snowbum, you might have to order an early /5 sender and hold the old and new one together. If they're the same, then use the older style one.

Still, makes me wonder what's going on.

All you need to do is type in your VIN number into the box on MAXBMW parts fiche or RealOEM parts fiche and this will tell you the bike details AND take you to the correct parts fiche for YOUR bike.

In your case: R100RT 79-84 (2474) VIN:6242151 Produced: 02/82 USA

Then go to the engine housing mounting parts to find your oil pressure switch:

61 31 1 243 414 OIL PRESSURE SWITCH - M12X1,5 0.07 1 $20.24

Looks like this (4 photos from MAX parts fiche):

I guess what threw me off is the info that says the other switches were supposed to fit. The early /5s had pressure switches that were M10 x 1 whereas the later switches were M12 x 1.5. So it would appear from the pictures that switch that came out of the engine is probably 12mm across the threads and like 1.5mm between thread peaks. Those other switches don't fit the bike.

Still think that VIN stamping looks weird.

20774 said:

I guess what threw me off is the info that says the other switches were supposed to fit. The early /5s had pressure switches that were M10 x 1 whereas the later switches were M12 x 1.5. So it would appear from the pictures that switch that came out of the engine is probably 12mm across the threads and like 1.5mm between thread peaks. Those other switches don't fit the bike.

Still think that VIN stamping looks weird.

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The VIN stamping _does_ look weird! It looks like it was cast and not stamped with the numbering tools. Very strange and never saw one that looked like that. A photo from a bit further back might shed some light? The 1.5mm pitch threads are probably what he has (or had) unless a PO substituted the wrong part I'm guessing... Also notice that BMW uses the split ring crush washer style there which Snowbum favours. I recall finding one on my oil pressure sensor and the dipstick washer. Maybe the fork bottoms on my old /5?

The raised numbers on the engine block.?... that is an illusion I'm not sure why but photography tricks your eyes sometimes but it is stamped, the numbers are stamped!



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frasermanx said:

The raised numbers on the engine block.?... that is an illusion I'm not sure why but photography tricks your eyes sometimes but it is stamped, the numbers are stamped!



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Click to expand...

WOW, that is a photographical optical illusion, I was trying to figure out how serial numbers would become sequential if each were case into the part.
At any rate, it is a different motor then what came in the bike, could be some previous owner noticed a leaky sender when he was installing the motor, taped a bigger hole and installed the wrong part.

The photo is definitely optically confusing. When I looked at it just now really quickly, at first the numbers looked stamped and indented. Then looking at it just a few seconds longer and the numbers look like they are proud of the aluminum around them. The engine must be from the twilight zone... or it's just a camera illusion...

Replacement blocks were unstamped. People sometimes stamped their previous numbers with hand help stamps and a hammer, resulting in a "non factory" appearance. Usually pretty obvious when done.

Friedle