The Airheads Beemer Club is a non-profit club reclaiming the 'Legendary Motorcycles of Germany'

Topic-icon Questions from Diode Board inspection

More
1 year 11 months ago #1212 by 14326
This is my second post regarding the inspection and refurbishment of the charging system on my '84 R100RS (Last Edition).

Please note from the 3 attached photos of the diode board from my bike:

I discovered that my diode board had metal mounts only on the top two mounts - rubber on the bottom 2. These two metal mounts (In the photo) appear to be homemade mounts, made with an allen head screw and a metal "tube" cut to the proper length.

The part number stamped on my diode board is 1-244-063-3.

The wire connecting the diode board's B+ terminal and the starter from my bike is included in the photo.

Question 1) Since the bottom two diode board mounting holes are insulated and only the two top mounting holes are electrically connected to the diode board chassis, is there any real benefit to using metal mounts at all four mounting points? (The two rubber mounts on my bike's bottom two positions appear practically new.)

Question 2) From the photos, does there appear to be any physical signs of damage or overheating other than the chipped grey paint? My basic static test was OK on all 3 poles. The grey paint still cover all the solder joints.

Question 3) Is this perhaps an original diode board given it's part number is 1-244-063-3? I couldn't find any reference to this part number.

Question 4) Is there a way to tell from these photos if the diode leads are "bent over" for better connectivity or straight through as they are on the problematic Wehrle boards?

Question 5) Does the B+ terminal wire (in the photo) appears to have been over heated? None of the other wires connected to the diode board show similar discoloration or deterioration.

J.S.
Attachments:

Please Log in to join the conversation.

More
1 year 10 months ago #1255 by 8166
Replied by 8166 on topic Questions from Diode Board inspection
I'd guess that the two lower rubber mounts were not replaced because it's a real PITA to get to the two nuts on the back of the timing chest. As long as the rubber is in good condition, as in strongly flexing the stud to bend the rubber shows no cracks, I suppose it's OK to continue using them, but just know that they will eventually fail. I make my own mounts from bar stock and thread the through hole for a socket head Allen screw. Makes installation much easier and a drop of blue Loctite makes sure that they don't come loose.

It's good practice to make a pair of jumper wires to connect the lower mounts to the stator housing. Use brown wire and eyelets on both ends. That will permanently cure any grounding problems.

I don't like the blistered paint on that diode board. Hard to tell from the photo, but it also looks like there's rust in several spots. If that's what it is, that's not good either.

You don't mention why you removed the DB to start with. Are you having charging problems?

Have you used an ohm meter to check each of the diodes? There's an article in the Technical Tips section of this web site describing the test procedure.

I also don't like the looks of that B+ wire, either. If it were mine I'd replace it.

FWIW, I've replaced all three of my BMW charging systems with either 450W or 600W systems from Motorrad Elektrik, which come with diode boards, voltage regulators, rotors, stators, and all of the wires mentioned here. That may be like shooting mice with an elephant gun, but I no longer worry about charging problems.

8166 Scot Marburger, This email address is being protected from spambots. You need JavaScript enabled to view it.
Check out the Yankee Hill AirTech Weekend, April 21-22, 2018

Please Log in to join the conversation.

More
1 year 10 months ago #1275 by 14326
Replied by 14326 on topic Questions from Diode Board inspection
Thank you Scot for your very helpful insights and comments.

My reason for taking on this job is primarily preventative. I'm trying to get this bike in shape enough to take on long cross country trips - and the more problems I can head off before I go, the fewer I'll have to face on the road. And of course, familiarity breeds reliability - the more parts on the bike I touch, the more I'll be prepared to handle problems on the road.

With the only modification of installing a high capacity AGM battery, I've only observed two issues that may pertain to the bike's charging system. 1) The dash voltmeter doesn't go back to a lower indicated voltage after a period of highway riding. I would think it would drop once the voltage regulator detects that the battery has been charged. 2) The dash voltmeter swings when operating the turn signals.

My plan is to renew as many parts as practical with new OEM parts showing wear. So far my parts lists include all the wires connected to the alternator and diode board, alternator brushes (the complete assembly), the voltage regulator, and the diode board. I haven't made a final decision about the diode board mounts yet, but I'm inclined to use all 4 (new) rubber mounts. However I plan to pay particular attention to grounding. I have a new "spider" wire that grounds the diode board to the timing chest and engine block - but I'm considering making a much beefier version of my own.

I don't understand your suggestion of grounding the lower diode board mounts to the stator housing. The diode board lower mounts are insulated and have no conductivity to the diode board itself. If metal mounts are used on the lower mounts - then grounding these mounts to the stator housing would be simply grounding the timing chest cover to the stator housing- bypassing the diode board. That doesn't make sense as the stator housing is mounted to the timing chest cover.

I'm pretty sure the stock 280W provided by the stock charging system will meet my needs - and plan to heed your advice about large capacity charging components - and use the savings for new tires for my long rides.

J.S.

Please Log in to join the conversation.

More
1 month 3 weeks ago #3824 by 7884
Replied by 7884 on topic Questions from Diode Board inspection
Rubber mounts will eventually fail and have to be replaced more importantly they don't dissipate heat which increases the odds of diode board failure. You may need to heat and bend a 8mm wrench and use tape to hold the nut but it's worth the trouble.

Please Log in to join the conversation.

More
1 month 3 weeks ago #3826 by Wobbly
Replied by Wobbly on topic Questions from Diode Board inspection
^^ That ^^, or you could take another approach. Here are 2 suggestions...

► One item that needs inspection (for possible replacement) at around 60K miles is the cam timing chain. This job is an easy "home mechanic" type job and involves removing the front engine cover. With the cover in your hand, converting the 4 diode board standoffs to all-metal is an easy job. You will need one BMW tool, the alternator rotor puller bolt, which is one tool that should be in your travel kit anyway.

Parts for that job include the crankshaft o-ring, the camshaft oil seal, cover gasket, chain, movable chain tensioner blade, and (most importantly) the updated and stronger tensioner spring. About $35 total from BMW Max.

► One reason for the discoloration is the heat created by the electrical current the alternator and diode board are having to handle. You can cut the amount of current being consumed by converting all your bulbs to LED. And the biggest current consuming bulb is the H4 headlamp. When you cut the current consumption you'll also be cutting the temperatures the alternator and diode board are seeing. LED bulbs will also have fewer issues while you're on the road.


BTW: Motorrad Elektrik sells the All Metal Diode Board Standoff Kit


Just some things to think about.

Don't hide 'em, Ride 'em !!
#15150

Please Log in to join the conversation.

More
1 month 2 weeks ago - 1 month 2 weeks ago #3828 by Wobbly
Replied by Wobbly on topic Questions from Diode Board inspection

14326 wrote: I'm trying to get this bike in shape enough to take on long cross country trips - and the more problems I can head off before I go, the fewer I'll have to face on the road. [snip] With the only modification of installing a high capacity AGM battery...


Just finished reading on the Motorrad Eliktrik web site yesterday about their High Voltage Regulator product. Most people might buy this to get better charging at low RPM, but a secondary aspect of this regulator is that it's set to a slightly higher charge voltage that sealed AGM batteries prefer.

A standard regulator will work fine on an AGM as far as general riding, but the battery simply won't have the longevity or all the cranking power it's capable of delivering.

From their web site..... motoelekt.com/charging.htm

It does maintain the battery at a higher 14.2 voltage than the stock regulator allows, which is closer to the designed best operating voltage of the entire electrical system and gives more reserve in the battery.


Don't hide 'em, Ride 'em !!
#15150
Last edit: 1 month 2 weeks ago by Wobbly.

Please Log in to join the conversation.

Moderators: Wobbly
Time to create page: 0.705 seconds