Back              Replacing the Hall effect Sensor        Back   

On BMW R series motorcycles. (Airhead)

 

The following is a step by step instruction sheet for replacing the Hall Effect Sensor in the Ignition timing unit (Bean Can) used on later BMW 247 series engines. It is based on my experience doing the work on several such units. The job is fairly straightforward but fiddly. I do not claim that this is an absolutely definitive instruction set. I have come across two variations that need different techniques. There may be more. If you came across something that isn’t included here, please let me know.

 

You will need the following:

 

1.      A new Ignition sensor. BMW used a Honeywell 2AV54 sensor (Hall Effect Vane Switch to give it it’s proper title).

2.      Fine insulating sleeve

3.      A small soldering iron and the ability to do fairly small and neat wire joints.

4.      A small ball peen hammer to rivet the new sensor in place.

5.      Outside circlip pliers.

6.      An 8mm Allan bolt

 

You do not need to remove the drive dog from the bean can. In fact, if you don’t have a problem with the bottom bearing, I would recommend that you don’t. The pin can be a real PITA to remove and, if you deform it, you will have a real problem. It is worth remembering that parts for the bean can are NOT AVAILABLE. If you damage any part beyond repair, you will have to get a replacement bean can!!! Work Carefully!

 

This is what you do:

  1. Remove the two Cross head screws and take the top off the can.
  2. Using a small screwdriver, prise the small cover out of the side of the can.

You should now see something that looks like this:

  1. Remove the two screws and lift the outrigger bracket out of the can

 

 

 

 

 

 

            

 

 

           You should now have something that looks like this:

 

  1. The big spring clip must now be removed. I have found the easiest way to do this is to insert one of the screws then use a screwdriver to lever against the side of the can to compress the spring.
  2. Next remove the ‘E’ clip from the central shaft.
  3. Working through the port in the side of the can, remove the advance springs from their posts on the advance mechanism. (These may drop down inside the can. Don’t worry about it, you’re going in there anyway.
  4. Now remove the three Pan head screws from the side of the bean can assembly.
  5. Use a screwdriver to ease the pip on the cable strain relief out of the hole in the can. The whole plastic section can slide upwards.
  6. Working carefully, lift the whole assembly including the outer part of the advance mechanism and the static parts of the sensor assembly out of the can. It will be necessary to slide the cable strain relief out of it’s slot as the mechanism comes out. Normally, tapping the can upside down on your hand will jar all of the bits loose but, if it is tight or corroded, it may be necessary to carefully use a lever through the side to remove things. DO NOT lever against the sheet metal shield at any time… if you distort this you are stuffed!

You will now be holding something that looks like the bit on the right in this picture except that there will be an outside circlip on top of the sheet metal shield:

  1. Remove the circlip.
  2. Now it is necessary to remove the sheet metal timing shield. It is very important that this isn’t distorted. I have found the best way to do this is to insert a 8mm allen headed bolt into the central hole, then, supporting the shield in one hand, tap the head of the bolt with a small hammer. This is enough to jar the shield loose from the advance mechanism. BEWARE! There is a small indexing pin between the shaft and the shield it will fall out as the shield is removed. DO NOT LOSE IT!

This is what you are left with:

  1. Remove the outside circlip and the timing plate will lift off the advance mechanism.
  2. Some cans have a plastic shield over the timing plate, some don’t. If fitted note it’s position and replace when reassembling.
  3. The timing plate is, in fact, two plates joined together and this is where I have found the variation in the design of different cans.  On some mechanisms, the two plates are held together by two screws. Simply removing the screws will allow the two plates to be separated. If you have this type, breathe a sigh of relief and skip the next section.
  4. If, on the other hand, your timing plate is the other sort, you need to do some extra work. On this sort of plate assembly, the two plates are held together by the central collar that is peened over. It is simple enough to file or grind the peened over metal away using a Dremel or file but then you are left with two separate plates which can’t be satisfactorily reassembled with any guarantee they’ll stay together. There are a number of ways this could be addressed but this is my way.
    1. Grind away the peened metal and separate the two plates.
    2. Remove the old Hall effect sensor (see below)
    3. Reassemble the two plates together.
    4. There are three countersunk holes in the lower plate. Identify the two of these that will not interfere with the fitting of the new sensor
    5. Mark through these holes onto the upper plate (the best way to do this is to use a drill that is the same size as the holes and use it to mark a centre in the upper plate).
    6. Drill the upper plate and tap to accept two screws.
    7. Identify two spacers or washer stacks the same depth as the distance between the two plates.
    8. Obtain two countersunk head screws and cut them so that they do not protrude above the level of the upper plate.

Click on this link for an alternative approach to fitting the Hall Effect Sensor

  1. OK, so now we have the upper plate with the old Hall Effect Sensor attached. Simply drill out the rivets that hold the sensor to the plate. Do I need to say ‘carefully’ again… the placing of the sensor on the plate is critical. Do not drill the holes oversize.
  2. Cut the wires from the old sensor. It is a good idea to cut the three wires at slightly different lengths so that the resulting joins are staggered when the can is reassembled.
  3. Supporting the new sensor by resting the tops of the rivets on something solid, place the top timing plate into position and rivet it into place. The rivets are soft metal and this is quite easy.
  4. Cut the wires to the relevant lengths and solder them to the old wiring as neatly as possible. Use sleeves to insulate the resulting joins.

Reassembly

  1.  Reassemble the two timing plates together… they are indexed and will only fit together one way.
  2. If the Bob weights have been disturbed, make sure they are correctly reassembled and move freely. A drop of oil will assist in lubricating. No special oils or greases necessary.
  3. Slide the Advance shaft over the central shaft making absolutely sure it moves freely. Again a drop of oil will lubricate.
  4. Engage the advance springs on their posts. Once again, ensure that everything moves freely and the mechanism returns fully.
  5. Slide the timing plate, complete with its shiny new Sensor into place and secure with three screws through the outside of the can. Note that you need to introduce the plastic cable strain relief into its slot in the outside of the can at the same time. Make sure the wires are clipped into place and are not going to foul any moving parts. If your can has the plastic shield, replace it into position.
  6. Fit the first outside circlip onto the advance shaft.
  7. Replace the timing shield onto the advance shaft. This will (should) be fairly tight so make sure that the locating grooves for the indexing pin are properly aligned. I have found that the best way to locate the shield on the shaft is to use a socket large enough to go over the shaft and use it as a drift to tap the shield into place.
  8. Now for the fiddly bit. Insert the indexing pin into it’s location between the shield and the shaft. A magnetic screwdriver or a small dob of grease is invaluable to help hold the pin in place. Tap it home using a small pin punch or suitable sized screwdriver.
  9. Locate the other outside circlip on the advance shaft
  10. Locate the ‘E clip on the central shaft.
  11. Soak the lubricating felt with oil and replace the outrigger bearing in place securing with two screws.
  12. Refit the top cover and the side port cover.

Congratulations. You now have a working Bean Can where, before, you had a rather fancy paperweight. The process seems a bit daunting, but, in reality, if you have basic skills and some patience it is quite straightforward. The only part that needs any real ‘engineering’ skills is section 15 if you need to do it. Even that is not difficult if you do the job carefully and methodically.

Here FWIW are a couple of pictures of the components of a completely disassembled can.

Part Numbers (added 6/9/07)

The OEM Hall Effect Switch used in the Bean Can is the Honeywell 2AV54 (at least in all of the bean cans I have dismantled), however, it is the nature of electronic components that, very often, other manufacturers will produce electronically and physically compatible products. By that, I mean that, while they may not look identical, they will fit and do the same job. The list below shows part numbers I have seen quoted as compatible. There may well be others and, if I come across them, I will add them to the list.  Please understand that have not personally used any of these except the Honeywell product and cannot vouch for their suitability.


Honeywell 2AV54

Siemens HKZ101 

Bosch 1237011052.

BB Automacao CYHME56

Availability(added 6/9/07)

New

The most reliable source I have found for the Honeywell 2AV54 is Newark-in-one in the USA. Of ordering from the UK, it is best to order via their sister company, Farnell-in-one based in Britain. You will save yourself a lot of money. Even so, there is a 'one off' delivery fee for products ordered from the US company. At the time of writing, this is about GBŁ15.00, which is more than the cost of the component. For this reason, I normally order five at a go and then offer the extras to anyone who might need them at cost (+postage of course). You might strike lucky and find that Farnell, themselves have one in stock but they don't usually keep them.

The Newark web site can be found at:

http://www.newark.com/jsp/home/homepage.jsp

and Farnell is at:

http://www.farnell.com/

In Australia and New Zealand, Jaycar stock the Siemens unit. They are at:-

http://www.jaycar.com.au/

Source for the BB Automacao unit:

http://www.bbautomacao.com/proddetail.asp?prod=VANE56

Used

Since these components are attached by riveting, I would not recommend using a second hand sensor. 

On the other hand, if it proves difficult or impossible to source new, it is worth knowing that a large number of cars, bikes and commercial vehicles use the same sensor. This includes, of course, most BMW K and R machines built since 1980 (don't know about the 'F' series). A trip to the local scrap yard should provide endless possibilities for obtaining a working replacement. It is beyond the scope of this article to attempt to list all of the vehicles but a good start would be to look up the vehicles that use the same Ignition Control Unit. I believe that many Vauxhall and Volkswagen cars of the 80's and 90's used this unit or a compatible one.

 

References and Links (added 9/9/07)

This section contains links to other related references on the web. Please note that they are the work of their specific authors and that I do not necessarily agree with what is said.

  1. Frank Warner describes how to add a second Sensor Unit to the bean can in order to provide a roadside fix for a failed sensor:

            

 

Disclaimer

The above is based on my experience working on a number of these ‘Bean Can’ assemblies. I am not a professional mechanic or a professional electrical engineer. While I have tried to ensure that the procedures are valid and accurate, I can take no responsibility for any damage caused or loss incurred while working on these assemblies. If there is anything I have got wrong, any variations I have not come across yet or any better ways to do things, please let me know and I will update this sheet accordingly.

 

Rob Frankham                                                Back

3/9/2007

Edited 5/9/07 - Typo's corrected

Edited 6/9/07 - Paragraphs added re part numbers and sourcing

Edited 8/9/07 - Link to page for alternate sensor fixing method

                      Additional Part number and source..

Edited 9/9/07 - Link to article re fitting second sensor.