TDM850/900 : Oil pressure sensor

How to add an oil pressure warning indicator.

One major issue with the 850cc engine is oil consumption. Unfortunately, oil consumption may lead to a major problem : a complete engine failure, along with a big hole in you budget. The TDM850 engine lacks a reliable oil engine check device : the window inside the engine casing is not very easy to look at, the bike must be strait up, engine warm, etc. Obviously, you need oil inside the engine to warm it, and if there is no oil, you must know before the engine is warm !

Having a device that warn the rider in case of a failure of the oil pressure is the best way to keep the engine alive. The most reliable way to check oil is to place a pressure sensor on the delivery pipe which feed the cylinder-head, after the oil-pump.

The XTZ750 (3LD), TDM850 (3VD & 4TX), TRX850 & TDM900 (5PS) share the same engine conception with a dry sump lubrication system and a separate oil tank, so the description thereafter may apply to all these bikes. Anyway, the TDM900 already comes with an oil level sensor (inside the oil tank) with a LED on the dash, its engine does not drink oil at all, due to a new cylinder ceramic coating.

I found a document on the net from Gabibbo (from Italy) which describe how to do it. The first two drawings presented here come from this document.


3D drawing
Original pipe location

The grey part on the 3D drawing is the original delivery pipe.
The original banjo screw (not shown) is replaced by an adapter on top of which the oil pressure sensor is placed.

The oil pressure sensor switch is normally open when oil pressure is during normal operation at about 0.6 bars.
It closes when oil pressure drops below 0.3 bars, and the warning indicator lights up.

Parts :
- Aprilia Pressure switch NC 0.3-0.6 bar / M10x1. Ref. : RSV 0956169.
- Brass adapter M10x1.25 male / M10x1 female. Ref. : Conrad 842168-55.
- Copper seals 15x10.5 (3 parts)

Other outputs

1 - Alex75 got an oil pressure sensor from Citroën :
• LN-A 0.7 2cyl mot.v06 652cc 26kw 01-1979 t/m 11-1983
• AXEL 11 m.g11/631 1129cc 42kw 02-1985 t/m 10-1989
Both sensors have a switching pressure level of 0.6 bars.
Available at Autoparts.

2 - leehenty had some fun machining a complete oil pressure sensor, to adapt it on the TDM. The pressure sensor is an Intermotor 50770 or 50910 and FAE 12290. Nice work !
You may contact leehenty on the Carpe-TDM Forum. You'll find there more infos about his work and you may also ask him for a ready made oil sensor.

Thanks to share ideas mates !

Electrical wiring

Wiring the sensor if very basic : wire a red light bulb (or a LED with a 470? resistor) from the sensor to the +12v (after main switch, fused).

The bulb will light on when the main switch is switched on, before the engine runs. This is normal as there is no oil pressure at this moment. The light will normally go off as soon as the engine is running and delivering a normal oil pressure. In case it does not goes off, stop the engine or you're in trouble !

(image)Wiring diagram.
The bulb is a 12V, 1W or so.
Wire the +12V to the main switch, after a fuse.

(image)Same as above except there is a LED in place of the bulb with a current limiting 470Ω resistor.

Other hacks...

(image)Complete oil pressure indicators are also available : e.g. Equus, check here : Conrad
It looks like the usual gauge indicator :


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