For me it's a daunting project (ST1100 alternator)
- Thread starter kiltman
- Start date
Well done and congratulations on sorting out the bike.
Was there a 1100 model year when Honda started installing the 40amp? Or did all 1100's have the 28?
1996 STs had the 40 amp alternator.
Up until then, the ST had the 28 amp alternator.
Question ... does anyone every replace the alternator preemptively? ie, they are 17-20+ years old. At what point might you consider changing it before complete failure? Sorry, I'm a novice.
You bet. If you read around this forum you will find that a number of riders have replaced their alternator because they didn't want to have a problem on the road etc.
There are others who waited and were fine.
I think it comes down to a comfort level.
OP
OP
There are a couple of us that have. As I outlined earlier I was noticing some issues. I have noticed that in Great Britain they tend to have more failures, and that is due more to climate than anything. My bike has been on the east coast for a number of seasons, lots of fine dust got in there. To replace brushes or regulators one has to remove the swing arm....maybe it's possible to do it without removing the swing arm but it sure makes getting at the alternator easier. I bought the alternator from ebay. https://www.ebay.com/itm/40-AMP-ALT...h=item4b3e30468a:g:MmQAAOSwm-ZatZX6:rk:1:pf:0
OP
OP
Probably one of the best and cheapest things to do is install a digital voltmeter. You can get them cheaply off ebay. Hook it up directly to the battery. I've installed a switch in mine. This way you can monitor the charging system. I have installed mine in the right pocket fairing lid. You would idealy like to see it charging in the 13.9-14.2V range. It will drop if you're running heated gear, but should run around 13.3-5 with heated gear or grips. If it's under 13V check the load on the system it's still charging but some gear won't operate at that low voltage like Oxford heated grips, they will turn off to save the battery.
John OoSTerhuis
Life Is Good!
I upgraded peemptively for more amps to run aux lights and heated grips and clothes. Quite a few others did the same. But no, all of our takeoff 28amp stators are long donated to poor STriders with failures. 
John
John
sirbike
Site Supporter
28 sec install.
Having previous tried to install the 40 amp on my 92 in one piece without success I split it.
This video helped me get the 40 amp into my 94 model in one piece.
Had to watch it a couple times though.
Having previous tried to install the 40 amp on my 92 in one piece without success I split it.
This video helped me get the 40 amp into my 94 model in one piece.
Had to watch it a couple times though.
sirbike
Site Supporter
I have an '02 so don't need the amps. I just don't want to break down 400 miles from home in the middle of nowhere. I am a backroads rider in sparsley populated regions.
CYYJ
Michael
In that case, I think the most appropriate course of action would be to install a voltmeter. To the best of my knowledge, alternators don't fail suddenly, like a tire puncture... instead, voltage output begins to fall off gradually, or the current the alternator is capable of putting out begins to fall off gradually.
There's a company close to you, Electrical Connection in Knoxville, that makes a little green - amber - red indicator light to monitor system voltage. It is very inconspicuous and easy to install. Or, if you prefer, you can get a digital display that shows actual volts such as this one from Aerostitch.
I have a 2001 ST 1100 with the original alternator and well over 100,000 miles - I have a digital voltmeter installed, and I'm quite comfortable riding it alone in sparsely populated regions. If I ever see the voltage falling off, I'll just cut electrical loads like the headlight by pulling fuses - that should be sufficient to get me back to a populated area.
Michael
OP
OP
You will probably be ok. Michael in the post above gives good advice. In the meantime I suggest you look at the main relay connector. It’s located on the left side, above the foot peg. Make sure it’s clean. That red wire has been known to overheat and compromise the connector. The bike is very dependable. Go out and ride
CYYJ
Michael
+1... no, make that +100!
Kiltman identified a far more serious potential concern for you than the alternator. When the "red wire" fails, it is a sudden failure, as in, "one moment it's working perfectly, the next moment the entire bike is dead as a doorknob". I had this problem happen to me this past summer. It cost $5 for the parts to fix the problem, and $500 for the disruption to my travel while far away from home. The red wire connection deteriorates slowly over time on all ST 1100s, and it's not a question of 'if it will fail', it's a question of 'when it will fail'.
See this post: ST1100 Total Electrical Failure.
Michael
I'm seriously considering the 28AMP to the 40AMP swap on my '91 with 15,000 miles I recently purchased. I already have everything to do the swap just trying to decide if it's worth the time and effort. If not, you'll see the setup for sale here on the forum.
OP
OP
If you are planning on keeping the bike for a number of years, I think it is definitely worth it. You only have 15k on the bike so you have some time. In the meantime deal with the connectors to the main relay, the three yellow wire connector and the connector to the voltage /regulator/rectifier. Inspect them clean them up and apply dielectric grease.
There is a loaner tool kit available to do the task, the job goes smoothly if you have the tools. I strongly recommend getting a new swingarm boot,oil seals makes reassembly a breeze.
The other pluses are running higher wattage headlamps instead of the 45/45 OEM bulbs. heated grips are nice too. I ran my 1990 for three seasons before the alternator gave out. I bought it with 129k kms and the alternator bit the dust at 184K kms. That bike now has the 40A alternator and is running like a dream, the new owner is lovin' this bike.
I think the age doesn't matter as much as miles. How many miles on your ST1100 ?
I replaced my 40 amp alternator with the Chinese alternator at around 95K miles. But my old alternator was working just fine. I replaced the brushes at 50K miles - the old brushes were worn only about 1/16th of an inch compared to the new brushes. My main concern would be with the regulator failing ( located inside the alternator). If you removed the alternator and the bearings still felt good and the brushes weren't worn much, I bet if you took the regulator to your local auto electric shop, they could match up a regulator they have have in stock. And they should also have brushes. And if the bearings feel a little rough or noisy, they could also replace the bearings. All these parts are standard, there is nothing magic about a ST1100 alternator.
There was a post ( somewhere ) about a guy who had his alternator fail. He took it apart and found a bad solder connection somewhere on the rotor. He re-soldered it and it worked after the repair. If you pull your alternator, I would check the solder connections on the rotor, too.
In hindsight, maybe I should have done all that instead of buying the Chinese alternator. But it looks like a well built unit and the price is right. I have the old alternator as a spare so the new alternator will never fail.
John OoSTerhuis
Life Is Good!
Screen name Moddy? It was a 28amp stator, Jim. Not the 40amper.
Edit: found David’s stator rebuild thread: Linky
John
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sirbike
Site Supporter
Data point
In 2008 I bought a 1994 with a dead alternator at 35,000 miles.
Then replaced with a 40 amp that had 80,000 miles and put 59,000 more miles
on that with no problem.
In 2008 I bought a 1994 with a dead alternator at 35,000 miles.
Then replaced with a 40 amp that had 80,000 miles and put 59,000 more miles
on that with no problem.