Frequently Asked Questions
Diagnostic Information
Before you can suspect any charging system component of failing you first should check all the easy stuff.  First make sure all the cells in the battery have
electrolyte up to the full line.  Use a hydrometer (a fancy name for a tube with floating balls in it) and check all the cells after the battery has been charged.  
You can get a hydrometer for only a few dollars at most bike shops.  The ones made for cars are way to big to use on 99% of bike batteries.  Once you are
sure you have a good battery...

Next check all the connectors. The battery cables and all the other wiring connections should all be clean and tight.  A weak or dirty connection can cause poor
charging system output.  A melted plug is also a sign of a loose or dirty connector.  The heat comes from the resistance of completing the circuit through oxide
(or oil and dirt) on the surface of the terminals.  If you use spray cleaner to flush out any plugs check for signs that the plug is being damaged from the
solvent and discontinue using it if there is.  Also use an air nozzle (or caned air) to blow out the connectors after cleaning them.  Some of the spray lubes like
WD-40 are good for cleaning out connectors but I do not endorse them as lubricants. Again check to make sure the spray lube is not damaging the plastic
plugs or insulators.

Bikes with mechanical voltage regulators may also need to have the points in the regulator cleaned or better yet replace it with an all electronic voltage

If you still have a charging system problem after this, then start working your way through the charging system with an electrical meter as described in the
repair manual for your bike.  If something doesn’t make sense, ask me and I’ll try to make it clearer for you.

2.  Do I need an expensive test meter to figure out what's wrong with my bike?

An inexpensive electrical multi-tester can be purchased for around $10~$20 at most home center stores. These are more than adequate for diagnosing
charging system problems and well worth the price.  I wouldn't be with out an electrical meter and I always have 2 or 3 of them around and I keep a small one
in my bags when I travel.

For testing rectifiers, a small battery and a light bulb wired together will give you an adequate test light.  So long as the light goes on when you touch the ends
of the leads together, it'll work for testing connections and rectifiers.
This is a schematic for a simple test light made with 2 AA batteries and a 3 volt
flashlight bulb.

3.  How do I to test a rectifier?

Start with one lead of the meter (or test light) to the positive lead on the rectifier.  Touch the other test lead one at a time to each of the AC
terminals of the rectifier.  At this point you will either have continuity or not but it should be the same with all the AC terminals on the rectifier.  
Swap the test leads (still working with the positive terminal of the rectifier) and repeat the test.  This test should have the opposite result as the
previous test.  Again the result should be the same for each of the AC leads. Move on to the negative lead off the rectifier and repeat the 2
previous tests.  This is test is easier with a test light than with an electrical meter.  The point is to check that power flows one way but not the other
and the exact numbers isn't as important.  If your meter has a buzzer for continuity, this works very well too. If the rectifier fails all tests with a
digital meter, it may not be the rectifier but that you're using the meter on the wrong scale. Set the meter to the diode test function and test it
again.  If your meter doesn't have this, it's time for a new meter. This will catch a bad rectifier 95% of the time. The rest of the time they only fail
under load and will usually get pretty hot.

4.  Charging system diagnostics for older Honda singles and twins (Pre-1978)

First off, read the above articles.  These things all need to be dealt with when you have a charging system problem.

There are 3 wires from the stator and depending on the year of your bike they will be different colors.  From 1969 on the colors were pink, yellow and white.  
The pink wire connects to a full charging coil, the yellow to a 2/3rds coil and the white wire to a 1/3rd coil.  The yellow and white wires connect in the headlight
switch when the lights are turned on.  What this means to you is that the resistance from pink to white will be a little less than pink to yellow.  You should get
around 3/4 to 1 ohm from yellow to pink and somewhat less from pink to white.  None of these 3 wires should have continuity to ground.  Check the stator
with an ohm meter and if it passes these test then move on to checking the connections.

The white and yellow wires from the split coils are connected together (in the headlight switch) when the headlight is turned on directing more power into the
charging system.   If the switch fails the charging system will not give full output.  To make this more confusing, most pre-1969 Hondas use the same system
but with different wire colors from year to year and sometimes model to model.  On these bikes the brown wire usually represents the full charging coil and
yellow and pink wires are from the split charging coil.  The best way to be sure is to check the wiring diagram in a repair manual for your bike. The best fix is
a new switch but they are usually no longer available.  Some people bypass this and connect the white and yellow wires together at the rectifier giving full
charging all the time.  This is only a good idea if you ride with the headlight on all the time.  

Proceed to the next article if you are still having problems.  Also see article #22 and the bottom of this page.

5. Why don’t you make a regulator for the old Honda singles and twins?

Change that, I now have a voltage regulator / rectifier unit that works great on the these old bikes.  This unit is built by an outside supplier to my
specs but it's a great part that I'm happy to put my name on...  See the VRRPM2-HCB on the
regulator/rectifier units page.

There are a few things to consider before buying one.  First are you running any electrical accessories that cannot handle a voltage spike over 14.5
volts?  If all you are running is the stock lighting, this unit is only an  optional item, but if you've added a radio, electronic ignition or a GPS,  a unit
like my VRRPM2 is a necessary addition to your bike.  

6.  All of the components in the charging system on my bike test out OK but it still doesn’t charge.  

This is almost always caused by dirty, corroded or weak terminal connections. Corrosion on the terminals acts as a resister dropping current flow and creating
heat.  The heat often ends up melting the plugs making the problem even worse.  The only fix is to clean all the connections and coat the terminals with
dielectric grease to prevent them from corroding again.

For more info on how to take care of this problem, go to the
connection cleaning and repair section.

7.  Diagnostics for 1979~1984 Honda 750~1100 DOHC fours (and SOHC CB650)

The following information also applies to the CB550 Nighthawk but the resistance on the field coil (black to white wires) is lower.  Honda has
released an updated stator/field coil assembly for this bike (this is the only bike I know that uses this arrangement) and I  recommend calling the
Honda dealer for this information as the manual may be wrong.

The first test is to test the voltage between the red wire on the rectifier / voltage regulator unit (do not unplug it for this test) and ground with the
bike running.  If you're only getting battery voltage then you have a problem.  If you're getting over 15 volts then the regulator is bad.

At first all those wires look rather intimidating but once you break it down it's rather simple.  Unplug both of the connectors and use the test
procedure above to test the rectifier part of the unit.  The red wire is positive and the green wire is negative and  test them against the 3 yellow AC

The next test is to test the voltage regulator.  Plug the small plug from the regulator / rectifier back into the wiring harness.  With the ignition on but
the bike not running and if the regulator is good, you should get less than battery voltage between the black and white wires in the large plug from
the regulator / rectifier.  You can do this test with the bike running but I find it usually doesn't make any difference.

If these test have positive results the next thing to check is the resistance on the rotor.  Remove the alternator cover and check the resistance
between copper rings on the rotor.  There should be 4.5 ~6 ohms resistance if it's good.  Most of the time when rotors are bad there will be either
infinite resistance (completely burnt out) or less than 2 ohms resistance (internally shorted.) Either way you're looking at getting a new rotor.  If the
rotor checks out good the next step is to check the resistance between the black and white wires (with the alternator cover installed.)  Wiggle and
tug slightly on these wires during this test.  If the resistance changes at all during this test or is different than the resistance between the copper
rings on the rotor, the wires leading to the brushes (black and white wires) will need to be replaced.  The wires to the brushes going bad is more
common than one would think

The next thing to check is stator.  I left this test for last because this is the least likely thing to go wrong.  There should be about .5 to 1 ohm
resistance between the yellow wires from the stator and infinite to ground if the unit is good.

8.  My bike drains the battery when sitting, how do I find out what's causing this?

Solder 2 wires on a turn signal bulb and insulate it generously with electrical tape.  Disconnect the positive cable off the battery and connect the turnsignal
bulb in-line between the negative post on the battery and the battery cable (do not try and run the bike with the bulb in the circuit.)  With the ignition switch
in the off position, the bulb should be out.  If it's lit, then something on your bike is draining power.  To find this, start unplugging connectors until the light
goes out.  The thing you unplug that makes the light go out is the problem.  

It’s also possible that the main wiring harness has shorted wires but if that’s the case, your bike will be regularly blowing fuses.

9.  If I plug a terminal into the wrong place in the housing, can I get it out?

This is easier than it looks but to avoid repeating myself, the description on how to do this is in connection cleaning and repair section.

10.  Is there a cheaper alternative to the OEM sealed beam headlights?

If your bike has a 12 volt electrical system and headlight is larger than 5 ¼”, you can replace the bulb with an auto sealed beam. This fix is perfect
for many older bikes with 6" round headlights.

Take an old dead sealed beam and tape up the glass with duct tape, put it in a paper bag,  then whack it with a hammer in about the center of the
lens.  Carefully remove all the broken glass and discard it.  With a die grinder or similar tool cut out around the bulb so there is about a 1" hole in
the back of the reflector.  Purchase a car 5 1/4" Halogen sealed beam and glue it in with a generous amount of silicone rubber sealant.   You will
need to get a plug for the back of the car headlight but many larger Japanese bikes use the same plug and it should be easy to get one at most
motorcycle salvage shops.  

This type auto headlight has an internal halogen bulb surrounded by a glass reflector and lens so if it gets hit by a rock and gets a small hole in it,
it'll keep on shining.  This should run you about $7 for the sealed beam and you'll use about a dollar's worth of sealer.  It'll also be about 50%
brighter but the Halogen bulb will draw a little more power.

For bikes with 7" round or odd shaped sealed beam headlights
Most 7" round sealed beams are directly replaceable with H4 lens/reflector assemblies that take a replaceable bulb.  However some OEM sealed
beams have and odd mounting system and will need to be either spliced like below or use a 7" glass sealed beam like above.

To make a spliced lens/reflector assembly carefully cut the factory sealed beam steel reflector about 1" above the bulb with  a die grinder with a
cut off wheel.  This will leave about a 2" diameter hole in the back of the unit.  Take a Automotive H4 headlight and cut it's lens about half way
between the bulb and the lens.  You will see that the back of the H4 unit and the front of the stock sealed beam will   be 2 cones that pretty much fit
together.  Clean them both well and glue them together with high temp silicone sealer.  It is very important to remember is to maintain the stock
bulb position in the sealed beam so that the lens doesn't over heat and crack and to get the correct light pattern.  You can cut to slits in the H4
reflector (from about 1/2" from the bulb to the edge of the cone so you can roll the cone a little tighter. Be sure and give the high temp silicone
sealer at least 24 hours to dry but over a weekend would be better.

Do either of these modifications at your own risk.  These instructions assume that you have some proficiency with hand tools and always wear
safety goggles and gloves when using a die grinder or breaking glass.

11.  Do special orders cost more?

For the most part they're the same price and only take longer.  If I have to use a lot more wire or get some special connectors I do not normally
have, then there will be a small additional charge.

12.  Why don't the parts you sell look like the ones that came on my bike?

The parts I sell are of my own design and construction.  Currently I cannot make parts that look like the ones from the OEM supplier in Japan so I
settle for ones that work better.  If you don't like how my parts look, then perhaps they're not for you..

13.  What if I'm in a bad mood and take it out on you?


14.  What are the limitations on the guarantee?

There are no special terms to the guarantee on my parts (except on VRRPM series units we have made for us) but I expect them to be installed
correctly as per my instructions.  Failed parts will be repaired or replaced at my discretion.  Before retuning any parts you need to eMail me and let
me know you are having a problem.  I’ll help you check it out so we know for certain that it’s the part and not something else.  On all VRRPM
series units the warranty is a no BS 2 years but like other parts we sell, you must got though the diagnostics with us before sending it back.  I
reserve the right to void the warranty on parts that have been modified.

I pay return shipping but I pay the shipping of the replacement / repaired part (
in USA only but not for replacements outside of the USA.)  The
guarantee is not transferable from bike to bike or from person to person.  How will I know if the part has been used on more than one bike?  I won’
t, so I trust you to be as honest with me as I am with you.

15.  What is your return policy?

Returns for warranty or exchange, no problem..  If you bought the wrong part, I'll work with you to get it straightened out.  On the other hand if you
just decide you don't need it, we charge a 25% restocking fee
and you must contact us within 60 days about your intent to return the part.  

If you installed it or modified the part in anyway, it's yours don't bother sending it back there will be no refund. If you do send it back,  you will have
to pay return shipping to get it back...  
No returns on custom orders.

16.  Do I have to use on line payments to buy from you?

I accept money orders and cashiers checks by mail.  Click here for our mail order form

17.  Do you have other bike parts?

For the most part "what you see is what you get."  I'm always looking for new stuff to add to my line but business growth is moving rather slowly.

18.  Charging system diagnostics for 1969 ~1978 Honda SOHC Fours.

An analog meter is preferred but digital meter is OK for these tests but you'll have to take into consideration the static resistance in the meter.  
This article assumes that you have basic proficiency with an electrical multi-meter.

Start by removing the left side cover and unplug the 8 or (9 pin on some models) plug from the alternator windings to the wiring harness. Set the
meter to the lowest resistance setting, Rx1 on an analog meter or 0 to 200 ohm scale (sometimes only labeled 200) on a digital meter.  On the
engine side test the resistance between the yellow wires in all combinations.  You should get .5 to 1.2 ohms resistance here.  Next check from the
yellow wire to ground and you should get infinite resistance (or the same resistance as air.)

Next check the resistance from the white to the green wire.  The spec here is 4 to 6 ohms but I've found that a little out either way is OK but more
than 1 ohm out is usually bad.  Next test either the white or green wire to ground and you should get infinite resistance.  The green wire plugs into a
ground connection but when it's not connected to the harness it shouldn't be grounded when unplugged.  

If all this checks out, move to the wiring harness side of the plug and Test the green wire to ground.  You should get no detectable resistance here
or in other words: the same resistance as when touching the meter probes together. If this is all good, plug the 8 (or 9 pin on some bikes) plug back

Now set the meter to DC volts and unplug the voltage regulator.  Turn on the main ignition switch but set the handlebar switch to off.  Check the
voltage from positive to negative across the battery then check the voltage from the black wire that would have plugged in to the voltage regulator
to ground.  If there is less at the black wire than at the battery, you have a wiring problem.  This can be tested by making up a fused jumper wire to
run from the positive side of the battery to the black wire on the regulator.  Then run the bike and check the voltage output.

Assuming the power to the regulator OK:  plug everything back together; turn on the main switch and the handlebar switch off.  Either hand a paper
clip from string or use a .002 feeler gage blade and lay it up against the end of the alternator case (where the screws are that hold the field coil are)
then pull it away.  The magnetism of field coil should bend the gage or hold the paper clip when you try pull it away.  This test proves that at least
the regulator is working a little.

Now test the rectifier as per article #3 on my FAQ page.

Set the meter back to the lowest resistance setting and test the resistance from the white wire to ground.  You should get the same reading here as
before when you did the test from white to green at the plug.  Any discrepancy here is a wiring problem.  Unplug the rectifier and check the
resistance between the yellow wire and once again you should get the same resistance as at the alternator plug.

If this is all OK then remove the ground wire from the battery then test the resistance between the red wire where the rectifier plugs into the
positive battery cable.  Then test from the red wire to the rectifier to the red wire at the ignition switch. There should be no detectable losses here.

Since the ignition switch is unplugged, test the resistance from red to black wires in the on position.  Any detectable resistance here is bad.

If you resolve all this and you bike still doesn't charge correctly, there is one more thing to do to prove the problem is in the voltage regulator.  
Start by running the bike until it is warmed up enough to idle properly.  Use a fused jumper wire and jump power from the positive side of the batter
directly to the white wire that plugs into the regulator.  This will give the bike full charging all the time so do not run the engine over 1500 RPM or
you risk boiling the battery and blowing bulbs.  With the engine running test the voltage output at the rectifier to ground with the engine running at
idle and 1200 RPM.  If you get good charging, you need a new voltage regulator.

19.  Are the shipment insured?  No, unless you choose express shipping on check out.  We ship by USPS priority mail.  These
shipments are  trackable in the USA so insurance is not needed.   However Priority mail shipments are not trackable overseas
and the cost of insurance is the same as express so for these orders, we recommend all overseas shipments to be by express
We are not liable for lost over seas shipments unless they are sent by express...

20.  Can your products be used with Anti gravity or lithium batteries?

Yes and no.  I do not support the use of AG or lithium batteries that require a lower than standard charging rate of 14.5v
with any of our regulators or regulator/rectifier units.  

Some less scrupulous sellers are peddling alarm system batteries for use on motorcycles.  These require a reduced charging
rate and even if the charging rate is capped at the lower voltage, they don't last long on bikes.  We would rather you use a
regulator from someone else than be upset with us when your AG battery splits open or lithium battery catches fire...

21.  Why don't you have your phone number on your website?

I tend to keep odd hours and I'm often asleep when people want to call.  Also I can talk about bike stuff all day and when I do, I don't get any work
done.  Feel homered if I share my phone number with you and please do not share it with others.  It works much better for me to answer questions
by eMail...

22. Coping with a weak charging system
(like on pre-1979 Honda singles and twins and T-series Suzuki 250cc and larger twins.)

Even with a properly functioning charging system, many older bikes with a balanced charging system will have a battery low
enough to where the electric starter will fail to start the engine in a week or so of regular riding with the lights on.  The
problem is made worse by installing a headlight that is actually bright enough to actually see where you're going. Replacing
the selenium rectifier with silicon rectifier will help but not solve the problem entirely. Selenium is an inefficient
semiconductor and has a high resistance when compared with silicon.  You can take advantage of this and gain a few percent
in charging system output. All of the Oregon Motorcycle Parts rectifiers use silicon semiconductors.

The obvious solution is to make the alternator produce more power.  However this is much more difficult than it sounds.  
There used to be several places that would Rewind the stator to produce more power but then a regulator/rectifier unit like
our VRRPM2 is mandatory not optional.  The problems with rewinding is is very involved if you want to do it yourself.  The
information is out there but I've never done it.  If you go with sending it out to be rewound, there's very few that do this
anymore and it's expensive when you find someone that does it.

The better and cheaper solution is to reduce the power draw as much as possible and use a larger battery if there is space for
it.  Using a larger battery takes some research but often there is a taller battery with the same length and width and then you
just have to make sure it clears the bracket and whatever is over the top.  This isn't always an option but sometimes it really
works out.

Swapping out the tail and signal bulbs with LEDs will save some power but the voltage regulators on these old bikes weren't
very good and without installing a regulator/rectifier unit like our VRRPM2 to protect them, LED lights won't last long.  

Other options include using a low wattage headlight bulb in the daytime.  The low wattage bulb trick was a cheap and
popular solution back in the days.  It involved drilling a hole in the headlight reflector and then using a die grinder (a
Dremmel tool will work) and make an opening large enough for a small light bulb socket.  Usually a pop-in one from either
an old car turn signal or dash light then wiring it to a hidden toggle switch on the back of the headlight shell.

Another approach was to mount a small light under the regular headlight.  Some 1970 and older Honda cars had a small
rectangular back-up light.  One of these mounted to the under the regular headlight does not look too out of place.  Another
advantage is that with this set up a halogen light can be installed in the sock headlight shell for better night vision.  If you go
this route, most states have some regulation on the distance a headlight must be visible.  A turn signal bulb meets the
minimum requirement without a problem in most states.  For some people using a trickle charger once in a while or at night
is a cheap and easy solution.

In the end your bike just might not make enough power for all the accessories you'd like to put on them and you will have to
decide which ones are the most important to you.

There are way more LED lighting options now than ever but LED headlights still are not bright enough for night riding.  I
considered carrying LED lights here at but they're so plentiful and cheap on eBay I felt it
wasn't worth my effort.  Needless to say I've bought a bunch of them to play with and someday I may put up and article
about this...

23. Over Charging on bikes with an electromagnet alternator

The problem is usually caused by a bad ignition switch or other connection between the rectifier output and the voltage
regulator power input.

The way it works is the voltage is sensed on the wire that feeds power to the regulator but the power output is on the wire
from the rectifier.  This is usually the main switched power lead but on some bikes have a separate wire from the fuse box to
feed power to the voltage regulator.

These 2 wires connect when the ignition switch is turned on and if the switched power wire has low voltage, the regulator
boost the output until it gets what it's set to produce.  

The way to test this it to with the ignition off unplug the regulator then turn the power on and test the voltage from the
switched power wire to ground.  Any difference in the voltage here from battery voltage will be the amount it over charges.

On Hondas the main switched power lead is black.  Yamaha and Kawasaki use a brown wire for this and Suzuki uses an
orange wire.

24. Finding out if the charging problem on a R5, DS7, RD250 and RD350 is the alternator or the regulator and rectifier.

To do this, start by running the bike until it is warmed up enough to idle properly.  Unplug or remove the regulator and
rectifier.   Make up a jumper wire with a 2 amp fuse and run power from the positive side of the battery directly to the green
wire from the alternator.   With the engine running test the voltage AC output at the 3 white wires from the alternator with
the engine running at around 4500 RPM.  If you get 40 or more volts AC the stator, rotor and brushes are OK.  If the voltage
is low or the fuse blows, the problem is under the alternator cover...

Do not hesitate to eMail me any questions you have about my parts -

Return to the Oregon Motorcycle Parts home page
Note: Revised return policy.  See article #15...