BMW K bikes (Bricks)

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robmack

robmack
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I'm helping a friend with his K75.  I've determined that one of the Hall effect sensors on his bike is failing, the other is good.  I have a spare K100 HES plate with two operational Hall effect sensors.  I'd like to replace the failing sensor on the K75 plate with one of the operational ones from the K100 plate.

I know to remove the failing sensor, I have to grind down the rivet to the plate and then knock out the old sensor.  However, best practice is to insert a brand new sensor and peen over its rivets with a tool.  Anyone have a suggestion how can I fasten the replacement I have to the K75 plate?


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Matthew-Brisbane

Matthew-Brisbane
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I just used bolts with lock tight on the nuts


__________________________________________________
1986 K100 RS Motorsport
1988 K100 RS SE
1990 K1 known as Barn Find 
2004 F650 GS known as DACK-DACK
 
#### K100 RS Project 
2011 R1200 GS known as Big Blue 
    

robmack

robmack
Life time member
Life time member
Did you punch out or drill out the old rivets? I read that alignment is critical when installing the replacement sensors and hope that the bolt-method you used maintains that alignment.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Matthew-Brisbane

Matthew-Brisbane
Life time member
Life time member
Yes drill out the rivets and bolted straight through the existing holes the 

the replacements HAL had the same mounting positions


__________________________________________________
1986 K100 RS Motorsport
1988 K100 RS SE
1990 K1 known as Barn Find 
2004 F650 GS known as DACK-DACK
 
#### K100 RS Project 
2011 R1200 GS known as Big Blue 
    

Dai

Dai
Life time member
Life time member
I used 4mm dome-head allen bolts. Getting the rivets out of the replacement HES without bringing some of the hard plastic with them is difficult, but it's not disasterous as long as some part of the recess remains to butt the dome heads against and hold the HES down.

- I cleared out any excess plastic first using a sharpened electrical screwdriver (if you can't see the full circle of the rivet it needs scraping)
- I then tapped the rivet out from the back very gently using the almost-closed jaws of a vice/vise as the support
- I filed the edges of the dome heads so they became a drop-fit into the rivet recess
- I also used blue Loctite on the bolt threads as you can't whack them down hard (obviously!)

You may find that the dome heads protrude slightly above the rivet recess but it's well below the HES platform.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

robmack

robmack
Life time member
Life time member
Guys, Thanks so much for the information. I'll tackle this job sometime this week or next and update here how it goes.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Dai

Dai
Life time member
Life time member
One last thing Rob: the centre of the rivet on the backplate is a point (not a clever idea but...).  With some care you should be able to file off the point sufficiently to make an area large enough to take a centre punch blow to guide the drill.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

robmack

robmack
Life time member
Life time member
Dai wrote:One last thing Rob: the centre of the rivet on the backplate is a point (not a clever idea but...).  With some care you should be able to file off the point sufficiently to make an area large enough to take a centre punch blow to guide the drill.
This is confusing for me.

- I've ground down the peening on the back of the donor plate which released the hall sensor
- I carefully removed plastic from the bottom of the hall sensor to expose more of the encapsulated rivets
- I've carefully tapped out the rivets from the top using a drift.  Some plastic broke off but very little
- I have bought 4mm x 9mm pan head screws to secure the sensor to the working plate

So, since I tapped out the rivets, I have nothing to drill.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Dai

Dai
Life time member
Life time member
Ah - you ground the rivets down. I drilled the buggers out! Confusion de-confused (I hope) Very Happy


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

robmack

robmack
Life time member
Life time member
I finished up the repair.

Replacing HES sensor on existing K75 plate.  How to rivet on the replacement? 68739910

To follow on with the steps I took from my last post, I enlarged the hole on the plate to 4.0mm.  I soldered the three wires from the replacement sensor into the loom and covered them with heat shrink.  I took my lathe and faced off two screws so that the height of the head was 1.2mm.  This gave clearance for the rotating vane.  I bolted the sensor on and used green loctite to secure the nuts on the back.  

The last step was to test each sensor to see if they were operational.  I built a HES tester based on the Oilhead hall sensor tester plans here.
Replacing HES sensor on existing K75 plate.  How to rivet on the replacement? Img_3911

Plugged in the tester and both functioned perfectly. My next plan is to try out the repaired HES in a working bike to verify everything is in order.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

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