Triumph Rat Motorcycle Forums banner
  • Hey everyone! Enter your ride HERE to be a part of September's Bike of the Month Challenge!
1 - 20 of 76 Posts

·
Premium Member
Joined
·
789 Posts
Discussion Starter · #1 · (Edited)
I thought I would spend a bit of my spare time while its raining outside to sit down and describe the 25 amp ND alternator as found on my 1998 Sprint Executive. Contrary to what’s been written before, motorcycle electrics are not as mysterious as people would have you believe. With a good understanding of the basic operation theory I’ll cover here, there isn’t anything complicated or mysterious about the charging system on our Triumphs. Additionally, it’s my belief that anyone capable of reading this and understanding it is capable of doing a teardown and component replacement on the ND 25 amp alternator…with one small caveat. One component, the rectifier, is a soldered in component. To replace this item you’ll need a good 40 watt soldering iron. The other commonly failed components like the regulator and brushes are easily replaceable with only a Phillips screwdriver. There are other components present that might be a bit of a challenge to service. I’ll cover those items and let you decide if you feel comfortable dealing with it, or if a trip to the alternator shop would be better.

The ND 25 amp alternator overview

Most people probably already know most of what’s this section. On the off chance that you’re completely unfamiliar with the alternator and how it works, here’s a close-up of what I’ll be describing.



The ND 25 amp alternator as used on various Triumph motorcycles is part number T1300000-T0301. The actual Nippondenso part number as shown above is 100211-4950. As you can see, it’s a compact device that can easily be removed and replaced as a complete unit.

The theory of operation is quite simple. When you turn the ignition switch on, the alternator draws a few amps of battery power to turn on its internal electromagnet, creating a magnetic field. The electromagnet is comprised of many turns of thin gauge wire wound over special shaped iron core mounted on a rotating shaft, collectively called a “rotor”. When you start the engine, the rotor and its battery powered electromagnet spins inside coils of heavy gauge wire called the “stator”. The mere action of rotating a magnetic field within a coil of heavy gauge wire induces a voltage in the stator that can be used to power devices. In essence, this is all the alternator does, however it does require a few other components to be a reliable source of power on a motorcycle.

Because of the nature of the alternators design, the voltage induced in the stator windings is of an alternating nature (AC) and it must be converted or “rectified” to a constant or direct (DC) nature for the devices on the motorcycle to use. This is done by the rectifier which converts AC to DC by letting the voltage only flow one way.

With nothing to control the alternator voltage output, the faster the engine turns, the more voltage the alternator puts out. This unregulated voltage could exceed system design voltage if left unchecked, and would cause serious overcharging issues of the battery and possible electrical damage to the igniter if not for the intervention of the voltage regulator. It is the voltage regulators job to sense voltage output of the alternator and hold the voltage as constant as possible given a varying engine speed and varying electrical demand.

Once alternator voltage output reaches the voltage regulator set point (~14.5 V), the regulator responds by reducing the amount of current passing through the rotors electromagnets (which have been using full current given to them up to this point). By giving the electromagnets less current to work with, the rotors electromagnetic field becomes weaker. With a weaker magnetic force spinning inside the stator, there is less voltage induced in the stator coils and therefore less voltage out of the rectifier. Once the system voltage drops below the voltage regulator setpoint, the regulator responds by allowing the rotor electromagnets to use more current which makes the rotating magnetic field stronger, which makes induced voltage higher. This is how the regulator regulates system voltage output and it has the ability to regulate this up and down rotor current action (and therefore alternator output voltage) within milliseconds of a detected system change.

As you turn on electrical loads like headlights, the system voltage sags or drops as that device consumes power. As described above, the voltage regulator senses this voltage drop and responds by allowing more current to pass into the rotors electromagnets making the magnetic field stronger. This causes a system increase in induced voltage, up to the regulators setpoint. In this way the regulator watches for system voltage dips as you turn on electrical devices and responds by bumping up rotor current to maintain system voltage at setpoint. As you shed load, the regulator reduces rotor current which drops system voltage to maintain set point.

On the 25 amp ND alternator, the regulator is mounted internally. Contrast this to the other type of alternator used on motorcycles that have windings mounted internally to the engine, use rotating permanent magnets mounted to the crankshaft instead of electromagnets on a rotor and require an external rectifier and regulator units. In this respect, the ND 25 amp alternator is much more like an automotive alternator, and that should come as no surprise. The ND unit as used on various Triumphs, Kawasaki’s and other motorcycles actually is a much smaller version of the ND automotive alternator. The smaller motorcycle alternator however works exactly the same way as its larger automotive cousin.

Generally speaking, the faster the engine turns, the faster the alternator turns and the more “power” the alternator is capable of producing for things like charging the battery and running essential electrics (essential electrics are the coils, the alternator itself, and the igniter). Because of the way that the alternator is constructed (the size of the wires and electrical rating of the internal components used), it is only able to produce approximately 25 amps at full output. If your electrical accessories demand more power than the alternator is capable of producing, you will slowly deplete the battery and at some point, there won’t be enough power to run essential electrics.

In cases where the electrical demand is more than the alternator is able to keep up with, it is sometimes possible to replace the stator coil and rectifiers for upgraded units for more power, but I am not aware of these upgrades to the 25 amp ND alternator. There are documented cases of fitting the larger 45 amp ND alternator in place of the 25 amp unit. With a bit of electrical wiring modification, it is possible and has been successfully done.

Electrical Block Diagram

Electrically, the 25 amp alternator is simple with only three components that typically wear. The rectifier has diodes that can short or go open, the regulator has pass transistors that can short or fail open and the brushes wear over time and lose electrical connectivity with the slip rings. Each of these components is easy to replace and the alternator does not have to be removed from the motorcycle.


25 amp ND Breakdown

You know where the alternator is and you know how to remove it if need be, but for general testing and minor component replacement, it is not necessary to remove the alternator from the motorcycle. I’ve dismounted this one as to completely strip it down and test and measure various components. Depending on what your intention is, you probably won’t have to be this severe.

Start by removing the rear cover from the alternator. It’s held on by three, 8mm nuts. Once you have the rear cover off, you can access the important components. After removing the rear cover, here is what you should see. I have labeled each component as to what it is and the picture also gives you a good clear shot of where the electrical connections go, so don’t be afraid to remove components for testing or inspection.



For general component testing, I recommend removing each component and test it off of the alternator. To do this, start removing all of the Phillips head screws visible in the photo. They will all need to come off and you really can’t mix up fasteners so there are no worries. You wont be able to completely remove the rectifier unless you either clip the wires that are soldered on the rectifier or unsolder them. Unless you suspect that the rectifier is bad, simply leave it in place and test it as described later.

 

·
Premium Member
Joined
·
789 Posts
Discussion Starter · #2 ·
Brushes

One of the first things you can check after disassembly is the brush length. Check the brush length against service minimums. Triumph lists the acceptable range as 10.5mm to 4.5mm minimum. The brushes below measured ~7 mm and had approximately 25k miles on them.



Slip rings


I removed the rotor so it was easy for me to measure. It’s likely you’ll have to completely remove the rear cover to get these measurements, so unless you’re going further into the alternator, you may have to assume that slip ring wear is acceptable based on the visual appearance of the brush tracks and if any deep grooves are present.


Regulator

There are three main terminals on the regulator: E, IG and F. The E terminal is the “Earth” terminal or ground terminal. The screw that fastens through this terminal electrically connects the regulator to the alternator chassis and ultimately chassis ground. The IG terminal is the “Ignition” terminal. This terminal is connected to a +12 volt supply that is on when the key is in the ON position. The IG terminal supplies power to the regulator. The F terminal is the “Field” terminal. The F terminal is the ground path connection between the rotor and the regulator. As mentioned earlier, the regulator allows more (or less) current to pass through the regulator and finally to ground.



To test the regulator, you need a multi meter set to read OHMS. I referred the Haynes manual for guidance as the factory manual has no information on how to test this device. I have two functioning regulators that I decided to test, and the results I obtained were significantly different from the Haynes reference table. While I can’t tell you if the Haynes data is right or wrong I can positively say that the two regulators I have are fully functional and work perfectly. After reading the differences between the two regulators, I actually went out and swapped regulators into my Sprint just to confirm things. The end result was that the alternator was fully charging and functioning normally with either regulator. As I can only comment on the two regulators I have, I would have to say that there is a fair amount of allowable variance in the resistance checks and still have a functional regulator. Based on the magnitude of difference between my data and Haynes data, I highly suspect the Haynes data is incorrect. You can draw your own conclusions and use whatever data set you feel comfortable with.

Rectifier

There are four solder terminals on the rectifier and one screw terminal. Three of the soldered connections are for the stator windings that connect the stator windings to the diodes. One of the soldered connections is the main output “B” that connects to output of the diodes to the battery. The one screw terminal is the “E” terminal that connects the rectifier case to ground.

You can check the rectifier while still attached to the stator windings (which is good) as to completely remove it from the alternator, you need a good soldering iron. Set your multi meter to “diode check” preferably, or if your meter does not have a diode check function, use the OHMS setting instead. Your readings should be as listed below.



For the average mechanic troubleshooting a charging problem, this is probably as far as you’ll ever need to go, except maybe to perform a rotor and stator wiring check. I’ll describe those later into the disassembly as it’s easier to show you what I am doing with things out of the way.


Digging Deeper


At this point in the disassembly, you need to have the alternator off of the bike, so if you’ve not done so, complete the task so you can get the alternator on your work bench. You need to disconnect the stator windings from the rectifier. You have a couple of choices here. One would be to clip the stator windings as close as possible to the soldered terminal on the rectifier. Snip all three windings and you can also snip the black wire that is attached to terminal “B”.

The other option is to use a soldering iron and unsolder the connections. You’ll need a good iron (I’d recommend a 40 watt iron at a bare minimum) and it would be best if the iron is“ESD safe”. The particular iron I am using is an ESD safe, analog controlled soldering station made by Circuit Specialists. This unit can be had for about 35 US dollars. For those that deal with electronics, it is a HAKKO 936 clone and it uses the same tips and heating element. I believe the unit is a 40 watt unit and it’s just barely large enough to get this job done. I’ve fitted the largest tip I had in my toolbox and cranked up the heat to 450 degrees C.

With the wires clipped or unsoldered, you can now remove the phenolic insulator from the stator windings and then lift off the rectifier.

 

·
Premium Member
Joined
·
789 Posts
Discussion Starter · #3 · (Edited)
Now that the rectifier is out of the way, you can continue disassembly of the alternator by removing the rear half of the alternator housing. The only thing that is holding the housing on at this point is the friction fit of the rear rotor shaft bearing where it presses into the rear housing. You’ll need to gently tap the rear half of the housing with a screwdriver or mallet enough that you can remove the housing. Use even pressure around the housing and tap gently and the housing should come off.



At this point, you can see the rear bearing, identified as a KOYO 83A837A


Rotor removal

To remove the rotor, you need to turn your attention to the front of the alternator where the drive impeller is located. The impeller is secured to the shaft with small bolt and what appears to be high strength fastener securing compound commonly called "Loctite". Remove the bolt by holding the drive impeller steady.



Because the drive impeller is securely fastened with high strength compound, I had to use heat from a propane torch to heat up the impeller enough to break the seal with the sealing compound. About 30 seconds of direct heat from a propane torch allowed me to lever off the drive impeller. Be careful as the impeller is plenty hot!!



Once the drive is out of the way, you can remove the three Phillips head screws that are holding the bearing retainer and preventing the rotor from sliding out of the housing.



 

·
Premium Member
Joined
·
789 Posts
Discussion Starter · #4 ·
Now that the rotor is free, you can see the front rotor bearing, identified as KOYO 949100-317



Not that you’ll ever have to replace one by scrounging through a junk box full of rotors, but on the off chance that someone actually needs the rotor dimensions, the rotor length is 129.56 mm long and the rotor itself is 76.4mm in diameter.


With the rotor is out of the way, the stator ID measures 76.87 mm. and the front oil seal is now visible and listed as NOK BE2408F

 

·
Premium Member
Joined
·
789 Posts
Discussion Starter · #5 ·
Rotor and Stator Checks

You can do both the rotor and stator checks while the alternator is still on the motorcycle.

Set your multi meter set to OHMS and start off with the stator wiring checks. You are looking for low numbers when checking between the wires. Less than 1.0 ohms is what you are after. Here, my stator wiring measures 0.5 to 0.6 ohms on all three wires.



Now check the wires for connections to the alternator case, which you don’t want. You want OL readings for these checks.

 

·
Premium Member
Joined
·
789 Posts
Discussion Starter · #6 ·
Likewise, check the rotor with a multimeter set to OHMS. The first check is the stator resistance check. It should measure between 4 to 6 ohms when checked at the sliprings. The 4.2 ohm reading is a healthy rotor.



Check each slipring for shorts to the rotor housing, which you do not want. Check as shown below. Look for OL readings which are good.



Congratulations

If all of your checks are good and all of the seals, orings and bearings are good, you can now proceed to reassemble all of parts you have on your table. I can honestly say that the assembly is straightforward and goes as easily. The ONLY issue I can possibly think might cause some hesitation to the first time rebuilder would be the replacement of the rectifier and having to solder in the stator windings. If you're not comfortable doing this (or lack the equipment, look for an electronics hobbyist or an amateur radio operator. They should have no problems soldering in the appropriate replacement for you.



Confessional

You sharp eyed viewers have probably noticed that something isn’t quite right with this alternator. I’ve given a few visual clues throughout the write-up that this isn’t a Triumph alternator. The parts look like a Triumph alternator, but there are a few parts that look odd and out of place, most notably the drive impeller is what gives the game away. I have to confess at this point that the alternator I’ve just taken to bits is actually a Kawasaki alternator from a ZG 1000, so your first bonus is that Triumphs and Kawasaki’s actually share the same alternator. This has been mentioned elsewhere, but I don’t think anyone has gone into one to actually confirm it. In this photo, the Triumph alternator is on the left, and the Kawasaki ZG 1000 alternator is on the right. I’ve taken the rotors off and you can see the difference in installed height and the reason you’ll need to swap drives. If you do nothing and attempt to fit the ZG 1000 alternator as is, the drive impeller will bottom on the Triumph cushions which prevent the alternator from mounting up completely. Mounting holes measure exactly the same on both units and the machined area where it fits into the engine is the same diameter…they really are identical units aside from the drive.




When I compared the voltage regulators earlier, I mentioned I had two. Regulator 1 is the actual Triumph factory regulator as fitted on a Triumph supplied alternator. Regulator 2 is the regulator from the ZG 1000 that I bolted in to the Triumph unit to test its function. Both work perfectly. This is actually a good thing to know as you can pick up ZG 1000 alternators off of Ebay for about 25 dollars. This means that for the price of a nice dinner, you can have a set of spare parts for your existing Triumph alternator and not have to pay the 800 dollars for a new alternator that the dealer charges.

Bonus Material


While playing around with alternators, I spent a bit of time to see what was available for replacement parts. You’re probably not at all surprised to find out that alternators between Triumphs and Suzuki’s are not the same, HOWVER the voltage regulator and rectifier used in Triumph 25 amp alternators IS common to the Suzuki GSXR 1100, so hiding under the disguise of a different alternator case is the exact same voltage regulator and rectifier that will work in the 25 amp Triumph alternator. The Suzuki prices are not much better than Triumphs, but I’m sure the delivery time would be much better.

Regulator #: 32500-27A00
Rectifier #: 31621-27A00
86-98 GSXR-1100
86-95 GSXR-750
96-00 GSF 1200

If those are still too pricy for your taste, there are aftermarket options available. Under the Transpro label, the KNVR-900 is listed as a replacement regulator for the above mentioned machines IN ADDITION TO…

Kawasaki ZX10, ZX900, ZX1000
Yamaha FJ1100, FJ1200, RZ700, RZ1000.

http://search.waiglobal.com/partnum.aspx?part=KNVR-900

A quick search on ebay has turned up a US supplier offering KNVR-900’s for 79 dollars, or about half of the factory price.

Conclusion

I hope you’ve gotten a bit of useful diagnostic information from this write-up. I had fun doing it and can’t wait to tackle the next project.

Ride Safe,
N5XL-Dave
 

·
Premium Member
Joined
·
789 Posts
Discussion Starter · #9 ·
Thanks Guys,

You've probably figured out by now I enjoy taking things apart to see how stuff works. Hopefully, someone can use the information to save themselves some downtime.

Mot, been meaning to mention for a long time now...I really like your site. Lots of great info there, and it was your site I that went to when I first picked up the Sprint so I could figure out how to completely drain the coolant out of the cylinder water jacket. This was way before I picked up the factory manual and the Haynes manual, so you've helped me without even knowing it. Here is a belated "thank you". :cool:

By the way, your site is one of the first places I check for reference material, followed closely by the T3 forum. I can't thank you and the people that post on the T3 forum enough for the things that I learn.

Ride Safe
 

·
Registered
Joined
·
4 Posts
ND Alternator Rebuild

Dave,

Thank you very much for your insightful write-up on the inner workings of the ND alternator. I now have the courage to rebuild my alternator, which probably needs new bearings. From your pictures, it appears that one of the bearings could be easily pulled using a small standard puller. However, the other bearing seems to have such a small gap between the bearing and rotor, I am concerned that I may not be able to easily pull that bearing. Any thoughts?

Thanks much.

Pat Duff
 

·
Premium Member
Joined
·
789 Posts
Discussion Starter · #11 · (Edited)
Dave,

Thank you very much for your insightful write-up on the inner workings of the ND alternator. I now have the courage to rebuild my alternator, which probably needs new bearings. From your pictures, it appears that one of the bearings could be easily pulled using a small standard puller. However, the other bearing seems to have such a small gap between the bearing and rotor, I am concerned that I may not be able to easily pull that bearing. Any thoughts?

Thanks much.

Pat Duff
Pat,
As a point of reference for you, I've had a good look at my alternator on my Sprint and I cant "see" any bearing wear issues at all. I am currently at 53k miles. I made that assessment based on the overall feel of the bearings as they spin. I cant "feel" any roughness when they spin, nor can I hear any abnormal noises. Additionally, I cant detect significant thrust of the rotor shaft.

That said, if you honestly feel the bearings need replaced, then my best advice would be to look for an alternator shop to do the replacement for you. Reason being is that the rear bearing removal could damage the slip rings if you're not careful. I wont discourage anyone from attempting to remove the bearings on their own as you certainly can...just pointing out a potential pitfall. Only you know your mechanical limits.

If I haven't scared you off then...
The alternator shop should have a plate made up for ND bearing removal where they use a shop press and press it off, but if not, the bearing will have to be heated so that it expands enough to be levered off of the rotor shaft. This can be done with a handheld propane torch if you're quite careful. Carefully heat the bearing the best you can while trying not to heat anything on the rotor. This is done by applying heat with the torch in a circular motion around the bearing inner area where it contacts the rotor shaft. You shouldn't need any more than about 30 seconds of carefully applied heat. Once heated, you should be able to carefully lever the bearing off. The replacement is much easier as you have the bearing in hand and can much more easily apply heat. Again, heat the inner part only enough to expand the metal so that it can be pressed onto the rotor shaft. An properly equipped alternator shop will have a press that can do this without heat.

The regulator, brushes and diodes are very easy for anyone to service...the bearings are significantly more difficult. Only do so if you really need to do so.

By the way, make sure you can source the bearings ahead of time. I don't think these are standard bearings and they will have to be ordered by either the alternator shop or a bearing shop. Take the pictures of the bearings with you from this writeup and have the shop tell you if they can get them before you pull stuff apart and are down for two weeks while parts come in. Of course this is also the time to replace the oil seal if you've gone this far.

One last thing. You're on your own for parts as Triumph does not offer bearings or seals for the alternator as replaceable parts. They consider the brushes, regulator and diode pack to be repair items as they don't expect you do dig this far into things. This is another good reason to discuss bearing replacement with an alternator shop before you go this far. If they cant source the parts, try a bearing house.

Another thought if you get in a bind and you have bad bearings and cant source replacement bearings would be to look for the Kawasaki alternator I mention in the writeup. Search for Concours alternator. You should be able to get these for 25-50 dollars on eBay and they are exact replacements (sans the drive impeller). Don't spend more than 50 dollars for one unless you are down and simply need one to get back on the road. Don't forget to factor in the availability and cost of a complete replacement from eBay might make the replacement cost of bearings prohibitive.
 

·
Registered
Joined
·
422 Posts
I know this may be a stupid question, but can someone point out to me the alternator bolt often referred to as possible source of a rattling noise? Is it shown anywhere on this thread???
 

·
Registered
Joined
·
77 Posts
Great write up as is the info in DaytonaCharlie's 26/40A swap thread-Thanks to all!

Does anyone know if it is possible(or advisable) to re-wind the 26A to produce a higher current? Obviously with associated wiring etc. upgrades. At this stage I am just looking for options rather than immediately going down the route of the Trophy alternator.

thanks,
Ed
 

·
Registered
Joined
·
4 Posts
ND Alternator

Dave,
Good thought about the bearing removal injuring the slip rings. I had not considered that. I would hope that the diameter of the shaft at the bearing is a bit larger than the slip rings which are about 14.5 mm. Hopefully Triumph can order the bearings. Thanks again for your insights.

Pat
 

·
Registered
Joined
·
16 Posts
Regulator

Hi do you know how much current the regulator passes.School was to long ago so I cant remember the formula to calculate the current flowing through the circuit.If we have that info I am sure that with a little research the unit can be repaired very cheaply.:)
 

·
Registered
Joined
·
16 Posts
regulator

I have just found what I think is the right formula and if I am right the regulator passes less than one amp at fourteen point five volts.Which if this is correct Jaycar sells the component for less than two bucks.Please note that repairing the regulator will require removing the regulator from the mounting by unsoldering and replacing the metal component which is a TO220 casing in which the regulator is an integral part of.
 

·
Registered
Joined
·
490 Posts
Thanks for the write up...I had a broken (well on the way out) regulator, i have replaced it with the modern version from Sprint manufacturing as it was half the price, but then MandP had it for £5 less so went with them... It works a treat, no more stalls at tick over.
 

·
Registered
Joined
·
22 Posts
Thanks Dave. My T-Bird puked its alternator, and kept blowing tail light fuses, on our way down to British in the Blue Ridge. You have given me more than ample options. By the way. Did you do the same with a starter?
Cheers!
 
1 - 20 of 76 Posts
Top