Mounting oil temperature and pressure gauges

The pressure and temperature gauge story so far: sensors installed, having sorted out the position of the oil pressure sensor so it wouldn't foul on the exhaust,  wiring harnesses made up to my satisfaction. Time to think through mounting the gauges themselves. The instruments on the mark 1 Trophy are mounted in a binnacle that bolts to the underside of the forks' top yoke. They are offset from the yoke and a bit of measuring suggested there would be room enough to squeeze in the the little gauges I'd bought.  

So the next question was how to mount them. With a bit more measuring, I could see an additional bracket would be possible to replace the bracketry they were initially fitted with. This new bracket would share the two M6 bolts that hold the main instruments in place. I'd already improved the firmness with which the main instruments are held in place so I was pretty confident about the security of this plan. I marked out my design on a bit of cardboard and cut it out to see if the idea would work in the space. 

The gauges came with a swivel mount attached to the front edge of their aluminium bodies. The only trouble with my plan was that the gauges would have to mount upside down because I'd need to attach them at the back of their bodies rather than the front. So I would have to reverse the guts of the gauges so my replacement bracket would screw to the rear edge instead, to solve the problem of the digits being upside down.

 So, idea demonstrated as feasible, I marked out the shape and holes I wanted on a 1mm aluminium sheet. I drilled the holes out before cutting with my jigsaw because it is much easier to drill into flat sheet than the something with bends in it. I decided to drill two possible mounting holes for the gauges so I could choose between two heights.

With the shape cut out, I clamped it in my pretend workmate and banged over the extensions for the gauges with a rubber faced mallet, then tidied up the roughness left by the jigsaw and drill with a my favourite fits.

 A trial fit showed the bracket was marginally too wide and the top edges of the gauges needed to move inwards and rearwards by between 5mm and 10mm to avoid fouling the top yoke and instrument binnacle.

I put a little bend into the aluminium to bring the gauges away from the binnacle (visible) and then another bend just inboard of the 90 degree bend to tilt the gauges inward towards the centre line of the bike (not visible).

I was now happy with the positioning of the gauges so needed to sort out the fact that they were upside down. I was also concerned that these car gauges might suffer in the rain. The electronics for the gauges are mounted on a small circuit board so they are on the opposite side of the mounting screw. Reversing this circuit board ran the risk of the mounting screw contacting the components. I solved this by cutting a piece of plastic sheet (actually the blister from the box the gauges came in) to insulate the electronics from the mounting screw. It was a bit of a fiddle to get it back in reversed with the improvised insulator but I got there with both gauges.

 I bought a box of o-rings in various sizes at an autojumble. I found some rings that were the same external diameter as the gauge bodies and coated them in rubber grease to help keep the water out. I gave my new bracket and the gauge bodies a coat of paint too.

 Here they are in place. I'm not sure about the purple anodisation. Purple and red aren't a great combination so I'll probably get the Smoothrite out again. Still, pretty neat, eh? They might even work ... ;-)

I don't need this pressure on - but I like it anyway

Inspired by Bostik, I decided to fit oil temperature and pressure gauges. The question was, where to?

The sump has three M16 oilway blanking plugs and the original 1/8NPT hole for the standard pressure switch. The pressure and temperature sensors I bought were both 1/8NPT and one of them (can't remember which) came with a clever but rather bulky four-way adapter block, drilled and tapped to 1/4 NPT and with four 1/8 to 1/4 NPT adapters. I fiddled around for ages with various alternatives for fitting the sensors. I decided to try using two M16 to 1/8 NPT adapters in place of two of the three oilway blanking plugs. I chose a drilling beneath the mesh filter for the main supply for the oil temperature sensor, and a drilling adjacent to the standard pressure switch at the rear of the sump for the pressure sensor. I think the latter is intended for an oil pressure test gauge because it doesn't blank a drilling in the sump casting that serves any other obvious purpose. 

I fitted the standard pressure switch and plug beneath the mesh filter for the oil cooler with permanent thread lock and torqued up nicely.

 The 1/8 NPT to M16 adapter plug for the temperature sensor should have been straight forward. Unfortunately, the one I bought had a fairly short thread and the blanking plugs in my sump are headless allen fittings which engage with a thread that doesn't start until approx 10mm into their respective holes. In other words, I got only two turns on the adapter before its head locked against the casting. Also, because these are tapered threads, the threads that were engaged were extremely loose. I've opted for two remedies. I ground down the head of the bolt to effectively lengthen it by about 4mm. I then wound PTFE tape around its threads to help take up some of the remaining clearance, if any, between the threads. I hope this will do the trick (clearly) but I'll have to wait for the start up to find out. This drilling is to an oil way before the oil pump so the oil will not be under pressure here. Unlike the take off for the oil pressure sensor ...

1/8 NPT to M16 brass adapter plug ready for temp sensor

The pressure sensor is pretty bulky and the exhaust headers run very close to the sides of the sump casting. There is a bit of room at the rear so I figured that would be the most likely place to fit it without interference between it and the hot pipes.

Aluminium 1/8NPT to M16 adapter plug with brass
three-way 1/8 NPT adapter, allowing a 90 degree bend
for the pressure sensor.

Even so, a test fitting of the sump showed very little room so I needed to put an 90 degree adapter in between the sensor body and the 1/8NPT to M16 bolt.  This aluminium adapter bolt was included in the gauge kit - a nice long tapered thread so no problem with engaging this one. I used PTFE tape again to give it the best possible chance to seal.

Pressure sensor body in place on the brass three-way adapter

Test fitting of pressure sensor, lined up against exhaust headers

I tagged the pressure sensor feed with
green tape so I wouldn't confuse it with
the temp sensor feed

Rats nest of wires sprouting in all
directions - 20 stripped ends to be
tinned for joining or termination

The sensors use a blue wire to connect to their respective gauges, the temperature sensor also has a white wire to connect to earth. The gauges need a 12v switched supply, earth and feed from their respective sensors. I made up two little looms to do this. I used 5amp blue wire to extend the temperature sensor, black for the earth and green for the pressure sensor.

The sensor mini-loom was for carrying three wires up from the sump to terminate above and in front of the battery. After scrutinizing the wiring diagram in my manual, I worked out that one of the connectors for the third ignition coil (unused on the four-cylinder models) is switched 12volts. It is a red female spade connector. The other one is brown with a yellow tracer and loops to the ignitor box. Not one to play with. Anyway, this unused coil connection runs very close to a place where the main frame tube joins to the box-section rear frame rails, next to the battery. There is a bit of room just here, above a useful little bracket that mounts the starter solenoid. Ideal for keeping connections out of the weather and tidy.

The gauge mini-loom was for carrying four wires (positive from switched supply, negative/earth, and two sensor feeds) from above and in front of the battery to the gauges which will be mounted between the standard clocks and the top yoke.

Four wires for gauge mini-loom: brown for switched supply,
black for earth, blue for temperature sensor feed, and
green for pressure sensor feed. 

Gauge loom ready for wrapping with electrical insulation
tape. I used heat-shrinking tube to seal the soldered joints and
additional, larger section heat-shrink to cover the whole joined area.

Sensor mini-loom, heat-shrink tube installed under the sump,
the other three wires (green for pressure, blue for temperature,
black for earth/negative) ready for wrapping. 

Termination of sensor mini-look: M6 ring for earth, male
bullets for sensor feed wires. Heat-shrink added to protect.

Cleaning threads with M6 tap prior to installation of sump

Pressure (left) and temperature (right) sensors in place on
sump with loom held out of harm's way with a cable clip. 

When I test fitted the right-hand exhaust, I discovered that the sensor body just touched. It might have been OK - but represented too big a risk of frying whatever is inside the sensor body. So I decided to remove a bracket the helps to locate the exhaust headers and to rotate the 90 degree adapter half a turn so the pressure sensor is now centralized behind the sump. In the picture below, it looks as though it is in contact with rear suspension drag link - in fact there is about 5mm clearance. So, no more interference, wiring in place - the job should be a good one. Only time will tell. If not, I'll have to replace the M16 plug and admit it was an adventure that failed.

Final (for now) position of the oil pressure sensor