Snowbum's BMW Motorcycle Repair & Information Website

2. Remove the tape from the regulator that keeps the top can from coming off.

3. Gently wiggle the top can off the base, these can be on tight, so work slowly.

4. Inside you will find a printed circuit board with all the components mounted upside down ....that is, underneath the board. On the end of the board OPPOSITE the plug/socket end, you will find a small electrical device called a pot (short for potentiometer). This is the factory adjustment control.  Every one I have seen is always sealed with a drop of a hard-to-remove white paint.

5. Try to remove or at least release the paint drop with repeated use of a WOOD-TUBE type Q-tip (some Q-tips use plastic tubing or plastic rod, that will dissolve in a solvent!) or a large common wooden toothpick, in something like acetone, MEK, or paint-remover-gel.  Clean off any gel, if you used that.   This can take some time.  If you are successful in not damaging the pot, it will be usable as is, and then can be adjusted. If you are not successful, you can THEN, paint droplet still wet from the solvent/gel, try VERY GENTLY prying a tiny bit at the paint, to free up the lower adjustment fingers metal ring. Do NOT pry much. I use a dental pick tool. As a last try before replacement, I have found it best to CAREFULLY unsolder the three legs of the pot and remove it, & soak it in acetone for a short while ....which ALSO gives me SAFE access to ENLARGE the very tiny hole for the adjustment, that is stock, on the board. If you are careful you could leave the pot in place & drill out that hole by hand...just don't ruin the pot.  You don't HAVE to drill the tiny hole larger, but you will then need a VERY TINY jewelers screwdriver for the adjustment,....so I DO recommend drilling the board hole larger. What size?   Whatever you wish, to match your jeweler's screwdriver  (or a modified nail) that FITS THE POT SLOT.  If you ruin the pot, it will have to be replaced, with any common 100 ohm pot that fits, or can be made to fit.  Try to be very careful, & not ruin the existing potentiometer!

6. Assuming the pot is operational, or the replacement will be installed; carefully enlarge the the circuit board existing hole for access by a larger sized jewelers screwdriver.

If you intend to make the regulator adjustable from outside the can (recommended), then you have an optional step to do now. That is to drill the thin metal cover in the appropriate place, and install a rubber grommet in the drilled hole. The purpose of the rubber grommet is to keep you from electrically shorting the potentiometer metal to the regulator cover metal when adjusting the voltage regulator with a metal-shank screwdriver.

You don't have to have the hole in the top of the can & grommet because you could set the regulator without the cover on.  The cover, whether on or off, has NO magnetic effects on the adjustment, so you CAN install the VR, make the adjustment with a very tiny jewelers screwdriver (cover off), and then simply replace the cover, using sealing tape.  This completely negates any need for drilling or a grommet.  It is your choice.  You can always add the hole and grommet later, if you want to.   Drilling the thin can metal, should you decided to do that, needs to be done with progressively larger drills or other tools, to avoid the drill from 'grabbing' the thin metal.

You WILL find the can hole convenient, but not absolutely necessary, for now ....and for future adjustments ....such as if you change the battery to a type needing a different voltage.   The more or less standard 13.8 volts as VR's typically come from BMW, is TOO LOW for modern batteries; and, I think it too low for the original flooded batteries.  If you use the hole & grommet, it's nice to seal it's hole with something.  I use, as noted well-above, a common black plastic or rubber auto-body plug, that fits into the grommet center hole, and I use a dab of silicon rubber sealant ...that stuff in a squeeze tube ....to keep that plug in place.  Easy to remove & readjust whenever you might like to, and the regulator remains weatherproof.

DO NOT mix up the information on the two holes.

7. Be sure all is assembled correctly.  Re-check your work.  Install the grommeted cover (if so done); be sure your jeweler's screwdriver will fit the pot slot rotate the pot back and forth a wee bit. If you are worried about the pot being OK, you could use an ohmmeter to prove that the pot is about 100 ohms between the ends, & that the wiper, with respect to either end, works properly on the ohmmeter as you rotate the pot wiper, before re-installing the metal cover.

8. Install the regulator on your bike & plug the cable into it.  If you did not drill the metal cover hole (and installed the grommet), leave the cover off and adjust the VR, ....then replace the cover and tape.

9. Adjustment of the regulator is by the jeweler's screwdriver, making SURE the metal of the jeweler's screwdriver can NOT contact the metal can (if can is ON, then you now know why I said to use a grommet). The screwdriver MUST be the right size, or you will ruin the pot. Be very gentle in any downward pressure when trying to engage the pot. The screwdriver works by fitting into a slot in the pot, to rotate the pot contact fingers.

10. The voltage setting depends on your usage of the bike, the type of battery, & the temperature of the regulator when making the adjustment.  Regulators are supposedly temperature compensated & thus DESIGNED to INcrease its voltage very slightly as the temperature of THE REGULATOR goes down.   Some don't do this well, so do the adjustments with the VR when cool, engine having been off before adjustment began.

Some guidelines & hints: