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350TSS · 17-09-2021, 09:34 AM

The project grinds on.........slowly.
I have tried a number of ways to obtain a 0.7mm air gap between the rotor attached to the camshaft drive pulley and the 3D printed plastic housing holding the pick up sensors. Plasticine was attached to the sensors and the 3D plastic part bolted on, unfortunately the plasticine was more resilient than the the 3D part resulting in the part bowing and the plasticine not really giving a clear indication of the air gap. The problem really is in the use of CF belt covers which are not the same dimensions at the three attachment bolt holes as the original moulded plastic belt covers.
Measuring with the depth gauge provides a range of results with a variability greater than the required air gap.
I have toyed with the idea of manufacturing a new sensor holding plate in 6mm aluminium but this will not get over the problem of variability of the depth of the CF belt cover and also I cannot work out how to attach the plastic encased sensors to the inside of the 6mm plate without infringing the air gap to the rotor. I will eventually find a way around it but "Lonely" my solitary brain cell is sorely taxed at the moment.
To resolve my electrical problem with the oil pressure switch I decided to go mechanical.
I purchased a pressure gauge from Aliexpress for about £6, it has a 40mm dial and a range 0 to 200 PSI. Ideally I would have liked one with a range 0 to 100 PSI but could not find one although the larger range means that the gauge will be operating well below its design tolerance and should therefore not be over-stressed by a M900 oil pump (max pressure at a guess would be about 80PSI).
It was advertised as suitable for pneumatic and hydraulic applications.
The thread on the input to the gauge is 1/8" NPT which I'd never heard of before (apparently an American thread, tapered and 27 TPI - wierd). Anyway, I bought a suitable tap and the required 21/64" drill. This is now not such a cheap fix.
I had some 10mm scrap plate to make a connection to the oil pressure switch hole but a 21/64" (8.33mm) hole with a tapered thread would not leave enough meat as it would almost certainly lozenge when the gauge was screwed in tight enough to be oil tight (and then it wouldn't be at all).
So I bought some 12mm x 25mm alloy flat bar, making the economic case slightly worserer.
I drilled a blind hole and taped it to take the gauge, cross drilled the plate to take a banjo bolt to thread into the oil pressure switch housing and then through drilled 3mm to connect the banjo bolt hole to the threaded gauge hole. The part was then shaped on my linisher (a belt sander inverted on my knees with the on switch locked on) put in the ultrasonic parts washer and blown dry and free of swarf with an air line. Here it is installed.

I turned the engine over on the starter (no sparks yet so I cannot actually start it) and the gauge quickly sprang to 40 PSI which either shows that the gauge is wildly inaccurate (entirely possible with cheap Chinese products) or I have very good oil pressure. I much prefer the second option.
Two issues with this installation, first a standard banjo union is between 8 and 10mm deep and a banjo bolt is sized accordingly so I now have between 2 and 4mm less thread engaging in the oil pressure switch hole thread. I will buy a longer M10 x 1.0mm stainless set bolt and turn it into banjo bolt and second the installation masks the oil filler cap, not really a huge problem as the bike rarely needed topping up between oil changes any way, it would just be a matter of cracking the banjo bolt and swivelling the gauge to get at the filler cap.

17-09-2021, 09:34 AM	#1332
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	The project grinds on.........slowly. I have tried a number of ways to obtain a 0.7mm air gap between the rotor attached to the camshaft drive pulley and the 3D printed plastic housing holding the pick up sensors. Plasticine was attached to the sensors and the 3D plastic part bolted on, unfortunately the plasticine was more resilient than the the 3D part resulting in the part bowing and the plasticine not really giving a clear indication of the air gap. The problem really is in the use of CF belt covers which are not the same dimensions at the three attachment bolt holes as the original moulded plastic belt covers. Measuring with the depth gauge provides a range of results with a variability greater than the required air gap. I have toyed with the idea of manufacturing a new sensor holding plate in 6mm aluminium but this will not get over the problem of variability of the depth of the CF belt cover and also I cannot work out how to attach the plastic encased sensors to the inside of the 6mm plate without infringing the air gap to the rotor. I will eventually find a way around it but "Lonely" my solitary brain cell is sorely taxed at the moment. To resolve my electrical problem with the oil pressure switch I decided to go mechanical. I purchased a pressure gauge from Aliexpress for about £6, it has a 40mm dial and a range 0 to 200 PSI. Ideally I would have liked one with a range 0 to 100 PSI but could not find one although the larger range means that the gauge will be operating well below its design tolerance and should therefore not be over-stressed by a M900 oil pump (max pressure at a guess would be about 80PSI). It was advertised as suitable for pneumatic and hydraulic applications. The thread on the input to the gauge is 1/8" NPT which I'd never heard of before (apparently an American thread, tapered and 27 TPI - wierd). Anyway, I bought a suitable tap and the required 21/64" drill. This is now not such a cheap fix. I had some 10mm scrap plate to make a connection to the oil pressure switch hole but a 21/64" (8.33mm) hole with a tapered thread would not leave enough meat as it would almost certainly lozenge when the gauge was screwed in tight enough to be oil tight (and then it wouldn't be at all). So I bought some 12mm x 25mm alloy flat bar, making the economic case slightly worserer. I drilled a blind hole and taped it to take the gauge, cross drilled the plate to take a banjo bolt to thread into the oil pressure switch housing and then through drilled 3mm to connect the banjo bolt hole to the threaded gauge hole. The part was then shaped on my linisher (a belt sander inverted on my knees with the on switch locked on) put in the ultrasonic parts washer and blown dry and free of swarf with an air line. Here it is installed. I turned the engine over on the starter (no sparks yet so I cannot actually start it) and the gauge quickly sprang to 40 PSI which either shows that the gauge is wildly inaccurate (entirely possible with cheap Chinese products) or I have very good oil pressure. I much prefer the second option. Two issues with this installation, first a standard banjo union is between 8 and 10mm deep and a banjo bolt is sized accordingly so I now have between 2 and 4mm less thread engaging in the oil pressure switch hole thread. I will buy a longer M10 x 1.0mm stainless set bolt and turn it into banjo bolt and second the installation masks the oil filler cap, not really a huge problem as the bike rarely needed topping up between oil changes any way, it would just be a matter of cracking the banjo bolt and swivelling the gauge to get at the filler cap.