Is it worth changing to a 40 amp alternator?

[gar]

I have a 1991 st100 which I got a few months ago. I was worried about getting one so old because of the horror 28 amp alternator stories but this one was just so well looked after I didn't want to pass it by. The previous owners had no reported problems and I thought I'd take the risk.

Is it possible for the bike to go throughout its life witout problems or is it almost certain that it will cause problems at some point?

As I'm interested in touring I don't want want to be stranded somewhere without the tools to do it myself and have to get a garage to do it - I know its a big job, engine out etc.

So is it worth doing it proactively?

 

[George]

You posted to the correct forum. Read the tips 'n hints 'n decide fur yurself. Lots of folks have done it, some have swapped out 28s with used 28s, readily available from those of us who have done the 40. Dollars 'n cents depending on which way ya go.

Worth doing if yur having problems and/or running lots of 'lectrical farkles. My 91 had 153,000 and 28 was working great when she got her 40.

 

[richpeabody]

I had the local shop (Circle Cycle) replace mine (knees don't work worth a crap anymore) and the thing works great! I spent about a grand, total, but figure that a tow would ruin that much plastic on a trip home if it failed.

 

[wjbertrand]

I wouldn't bother with it unless you plan to add a lot of higher draw accessories like lighting and heated gear. Electronics don't pull many amps. Of course if it shows signs of trouble I'd replace it before any long trips and I would not think of putting another 28A one in as the cost to upgrade is very minimal unless you snag a good 28 for free somehow. The amount of work is similar in either case.

To help your current unit survive, closely inspect and clean the harness plug on the regulator/rectifier unit under the left side cover. Make sure all the spade connectors are good and tight. Also consider removing the red 3P plug from the stator and soldering the wires directly, also under the left side cover. All of these junctions have a history of becoming loose, corroded and developing high resistance. This seems to be a precursor to stator failure.

I was one of the early upgraders on my '93 when my 28A one failed just as the group learned that the upgrade was possible.

 

[DeanR]

Jeff, do you have any pics of the plugs/connectors that you refer to?

 

[George]

Dean, ya don't need pics. White connector on the bottom of the VR/R and red connector on top of the main fuse - starter relay. Both are on the left side near the battery.

I'm sure there are pics here, probably at on of John Oo's photo albums.

Disconnect those two and look for signs of heat damage. If all looks good, don't worry 'bout it. If heat damage is apparent take appropriate actions.

Keep us poSTed.

 

[tmoney]

Having just completed the upgrade this spring, I would recommend doing it. I purchased a used 40A on ebay. Got a good price and then got help with the install. My post about the upgrade is on the site along with many others.


I put in a voltmeter when I first got my 95. This way I was able to keep an eye on what was going on. My 28A was working fine when I pulled it, but now ride with peace of mind regarding my electrics

 

[Doodaa]

I can't remember where the thread is located, but looking at your place of origin, I recall reading about some of you "chaps" on that island preferring the 28 amp due to corrosion problems. Something about the 28 being internal and the 40 is exposed to the elements.
I have the 28 amp and wasn't planning on changing it until necessary. I have installed a charging monitor, having had that problem with some of my other bikes. I have minimal electrical demands, no heated gear, but am currently shopping for auxiliary lighting of a low demand LED type.
I'll cross the alternator bridge when I have to.

 

[Flookyk]

Gar, as others have pointed out, as long as you don't need the extra output than I would suggest not do the upgrade, especially if you keep your bike outdoors.

If it goes, there are some 28A replacements on ebay now and then, the 40A ones tend to go fast and for more money and a new one, even from David Silver is now around ?600.

To explain the "outdoors" bit, with you being in the UK and the salt we use on the roads, if you ride in the winter and keep it outdoors you may well find the weakness of the 40A alternator in that the road crap enters the air cooling slots in the alternator and then corrodes the stator until it expands, cracking the rear casing.

This then moves the rotor in it's bearings and seizes the alternator (and engine) or damages the rotor.
If caught early enough it can be repaired but, if like mine, may take a while to find wires coming off and having to strip down the swingarm each time to sort the problem out.

Whoever designed the alternator to be fitted where it is (with open vents) right where it gets all the road crap (salt) off the road and any coolant leaks from in the V of the engine should have been shot.

 

[Bigmak96]

There is a 40amp Alt on Fleabay now. I posted the link to the sale post in the "For Sale" forum.
Mark

 

[ESB]

For only a 12 A gain, the 40's not worth it. The 28 (336 WATTS) puts out plenty of power. +1 on clean VRR and connectors, and don't overload, that's the key. Good Luck.

 

[Hound]

+1 on keeping the 28A alternator in the UK climate. My '94 1100P had the oil-cooled 28A and never missed a beat. My '99 1100P ate two air-cooled 40A alternators due to corrosion inside the casing. Ok, police bikes aren't pampered but it wasn't neglected either - it just got all that road spray up inside the casing slots. If you can find a police-spec VRR with the big cooling fins, or a copy of it, that will help your 28A to stay fit!

Definitely check those connectors as Jeff suggested!

And as mentioned, LEDs have a very low draw so no worries with that. You already have 55/60W H4s as standard and heated grips won't faze the bike much either.

 

[FieSTa45]

I am SO glad I hooked up with this group! I have a 91 ST1100 with 61K. After reading the tech items on this 28 vs 40 amp change, I will keep with
the good old stock unit. No high output lights only heated grips. I do not cash flow to go with the upgrade.......
Thanks guys!!

 

[SilverSTreak]

I am SO glad I hooked up with this group! I have a 91 ST1100 with 61K. After reading the tech items on this 28 vs 40 amp change, I will keep with
the good old stock unit. No high output lights only heated grips. I do not cash flow to go with the upgrade.......
Thanks guys!!

Well, I hate to bust your bubble, but the ONLY time my '91 ST1100 stranded me out on the road was at 60K miles when the 28 amp alt went south - and I had NOT been running ANY heated gear up until then... I was 200 miles from home!

As for the upgrade, it ISN't all that bad. The Engine DOES NOT have to come out. I read up on the various forums, and did mine in one 8 hour day with no help - yeah, there were folks that dropped by, but any help they provided was offset by the distraction ;-)

If it was me, and I was planning on riding away from home much, I'd bite the bullet and DO the upgrade... - Heck, just realized you're in MN - I'd do it anyways just so I could run heated grips and jacket frequently...

 

[Andi As]

Its a pity theres no top box mounting solar panel available that could supliment a standard alternator charge circuit then you might not need an upgrade