Ignition Sensor Overhaul

This post describes the overhaul of the ignition sensor (bean can) of my ’84 R100RS.  The overhaul is accomplished in the following steps:

  1. Disassembly
  2. Cleaning
  3. Lubrication
  4. Installation of a new JPT connector
  5. Installation of new cork lining on the ignition sensor lid
  6. Reassembly

The sections about the installation of the new connector and cork lining are in separate posts. They can be viewed by scrolling down to them or clicking their links above.

Several other individuals have published information about their Ignition Sensor Overhauls – links to two of them are included here:

Note: The photos in George Turski’s post show an Ignition Sensor that’s slightly different than mine.  The flyweight’s on my Ignition Sensor have plastic parts attached at either end – and on one end that plastic also serves as a bushing for the pivot pin.  The flyweight’s in George Turski’s photos don’t have plastic – and that may effect their need for lubrication.  The photo’s in George Turski’s post also show an additional washer between the driven cog and the canister. There may be other differences – I know of no factory documentation or illustrations.

Disassembly

Step 1: Remove the spring around the pin in the driven cog.

bean-can-dis-1

Step 2: Place the ears of the driven cog in a vice or something similar so you can drive the pin out without damaging the bushings.

Step 3: Remove the washers under the cog for cleaning. There are two thin metal washers and a “fiber” washer between them.  In my case, the “fiber” washer appeared to be plastic with a very small waffle texture.

bean-can-dis-4

Step 4: Using a edged device (not too sharp), remove the plastic rivet from the electrical outlet. Then remove the three screws around the sides of the housing.

Step 5: Remove the two screws securing the lid, and remove the lid. I used a channel-lock pliers to grasp opposite sides of the lid and was able to remove the lid by gently pulling from either side.

Step 6: Remove the two screws securing the outer bushing bracket. Then using a pair of pliers grasp the tang on the large retaining clip and remove it from the housing.

Step 7: Prepare the shaft to be driven through the inner bushing by filing away any burrs around the hole for the pin that secured the cog.  There is a seal the shaft passes through and insuring that there are no burrs on the shaft may reduce the risk of damaging the seal.  Once smooth, tap the shaft through the bushing with a punch.

Step 8: Withdraw the shaft that holds the flyweights and hall sensor.  Be careful to loosen the electrical connection from the housing as it may stick.

Step 9: Remove the two washers on the shaft.  The “fiber” washer is the outer washer and touches the housing, the thin metal washer is the inner washer and touches the flyweight base plate.

bean-can-dis-15

Step 10: Remove the circlip and snap-ring from the shaft.

Step 11: The small pin securing the “umbrella” must be driven out.  The snap-ring below the umbrella must first be rotated so that its opening is aligned with the channel that the pin must pass along.  Then secure the flyweight base plate and drive the pin through to the inside.  Be careful not to lose the pin.

Step 12: Remove the snap-ring that is at the base of the umbrella and remove the hall sensor from the shaft.

Step 13: Remove the flyweight springs. Then remove the flyweight outer shaft. Find the small metal washer between these parts that may be sticking to either side.

Step 14: Remove the circlips from the flyweight pivot pins, and remove the flyweights. Note that there is a washer under each circlip seated around the flyweight’s plastic the plastic bushing.

Here’s the layout of all the parts I disassembled:

bean-can-dis-30

Cleaning

My favorite tool for cleaning small parts is a Dremel tool with a Scotch-Brite type attachment.  These come in two different levels of coarseness.  The ignition trigger housing has a smooth flat surface that mates to a fiber washer.  I cleaned it with the Dremel tool, but was unable to remove the small pitting on it’s surface.  The Scotch-Brite attachment was able to polish it to a mirror surface.  I don’t think the Scotch-Brite attachment should be used however on polished shafts or bushings. An assortment of Scotch-Brite pads, Q-Tips and soft cotton cloths were about the only other cleaning products I used.  Not knowing the sensitivity of the seal on the inner bushing, I was reluctant to use any solvents.

bc-assy-1-dremel

Lubrication

Robert Fleischer states that the perscribed lubricant for the ignition trigger’s ATU’s shaft is BOSCH FT1V26 (5-700-005-005) in his section on chemicals. He doesn’t specifically state that should also be used on the inner and outer bushings – but as FT1V26 is a bearing grease, I’d guess that was the grease to use.  I couldn’t find this grease for sale anywhere on-line – but from these photos, it does appear to have been available in the past.

There is a gap between the inner bushing and the seal that seemed appropriate to grease.

bc-assy-outer-bush-showing-grease-in-ridge

I applied a very thin wipe of grease on the outer bushing, and I applied a very thin wipe of grease between the flyweight outer shaft and main shaft. Both seemed appropriate.  The flyweights on my ignition sensor have plastic bushings for their pivot pins.  I’m not sure they need lubrication at all.  I did put a thin smear of grease on the pivot pins to help prevent corrosion – although I found no corrosion present on disassembly.  I put a thin smear of grease on the small washer between the flyweight outer shaft and the baseplate.  I didn’t apply grease on the large thin washers touching the fiber washers – nor on the fiber washers.

bc-assy-flyweights-0

Various web sites mention using other lubricants for distributor shafts – from dielectric grease to Super Lube. Standard distributor cam grease is recommended by some.  Seeing how the ignition trigger mechanism worked, it seemed that almost no grease was needed at all – other than to maybe prevent corrosion.  There was very little friction on any of the components.

I decided on a “tip of the spear” choice of BMW’s “wheel bearing and small parts” grease. (BMW part number: 82000419622)  I found no reference to this grease’s use anywhere – so as far as I know, I’m the first person documenting its use for this application. According to it’s data sheet  this grease has a fairly high drop point of greater or equal to 220C – perhaps high enough for the airhead’s operating temperatures. I also found an old LUCAS reference to distributor lubrication. While LUCAS was surely the prince of darkness, it appears its distributor’s need for lubrication was not too severe.

Installation Of The New JPT Connector

click here

Installation Of New Cork Lining

click here

Re-assembly

Step 1: After lubricating the flyweight pivot pins and main shaft with a thin film of grease, reattach the flyweights on the pivot pins, place the flyweight outer shaft on the main shaft, and reattach the springs.

bc-assy-flyweights-2

Step 2: Place the hall sensor onto the flyweight outer shaft, and install the snap-ring closest to it. Be sure to rotate the snap ring so the opening is away from the small pin channel so that it will not allow the small pin to pass past it.

bc-assy-hall-install-1

Step 3: Place the flyweight baseplate on a secure place, set the umbrella on the flyweight outer shaft – seated against the inner snap-ring, and drive the small pin into the slot until it’s below the ridge for the outer snap-ring.

Step 4: Install the outer snap-ring on the flyweight outer shaft and the circlip on the main shaft.

Step 5: Place the then metal washer and then the fiber washer on the shaft and then insert the shaft through the inner bushing. Be sure that the mating surface for the fiber washer inside the housing is smooth and free of corrosion. I did not apply grease to this surface because I the fiber washers seemed to function properly dry.

Carefully seat the electrical connection into it’s slot. Re-attach the plastic pivot pin by simply pressing it in. Install the three screws on the outside of the housing that secure the hall sensor.

Step 6: Reinstall the large retaining clip and position it so that it will retain the electrical connection. After applying a thin layer of grease on the other bushing, install it with two screws. Then install the lid with two screws.

Step 7: Re-install the washers and driven cog. Re-insert the cog’s pin – being sure to secure the cog so that the force of driving the pin does not damage the outer bushing.  Re-install the spring over the pin

Step 8: I installed a new o-ring on the housing, and smeared a bit of silicone grease on it to allow it to more easily seat into the engine.

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