ST1100 Alternator housing cutout?

[DeanR]

I hope to install this 40 amp alternator on my '91. It had been put on a '94 at around 30 K miles, removed at 140 K. As you can see, the rear cover looks to have a cutout made in it. Anybody know why this would have been done, is it necessary, should I use it as is, or would it be a good idea to get a new cover for it for 15 bucks.

 

[sirepair]

Probably done for clearance, should not be a problem to use it as is. If you are concerned, cut a piece of inner tube and make a flap to cover it once it is installed.

You may want to replace the bearings and brushes in it before installing. I "rebuilt" mine before installing it a few years back. Write up on "the LiST".

 

[ST1100Y]

It probably eases the installation.
IIRC had the frames of the early years not enough clearance for the larger 40A alternator.
And IIRC-2 is it required to take parts off the 40A alt when doing the installation with the engine in the frame, as you won't have enough clearance to swivel the thing in place without jamming it in the case opening, risk of damage to the O-ring if not seated parallel.

 

[DeanR]

Thanks for that link Pat. It spins freely and smoothly. "Rebuild" still a good idea? I'm gonna try to get it tested this week if possible.

 

[sirepair]

Dean,
With 110K miles on it, I would rebuild it. It's a PITA to get in there, and I wouldn't want to do it twice if I didn't have to....

 

[John OoSTerhuis]

The cutout is necessary and is documented in the upgrade procedure. Remove the cover, install the alt past the frame crossmembers and then reinstall.

John

 

[DeanR]

Thanks John. So you are saying just leave it as is. Would you replace the innards too? Fair amount of money involved. It feels fine and hopefully will test as good, but does have a lot of miles on it. Have no idea what is involved to test it.
I'll be doing a kit request in the near future. Maybe tapered head bearing kit as well !

 

[DeanR]

Does anyone happen to have the Denso part no. for the 40 amp alt? I can't make it out on the Denso sticker. The shop tells me it would be useful to have that number.

 

[sirepair]

Dean,
I zoomed in to one of the pics and can ALMOST make out a number! Looks like 197211-157, but I'm not sure. See attached:

 

[DeanR]

Well, seems that there is an alternator shop about 5 miles away! Left it there yesterday and just got a call that it checks out ok. He was able to spin it up with some type of pulley that he's used before. Said he had no problem getting 35amps out of it without really cranking it. So, just have to now decide on renewing the innards or not, before doing the install. He said he could do it all if I wanted him to, or maybe just pull it apart properly for me to work on.

 

[ST1100Y]

He said he could do it all if I wanted him to, or maybe just pull it apart properly for me to work on.

Well, did the shop guy diagnose anything in need of overhaul, like bearing noise, worn brushes?

 

[DeanR]

Well, did the shop guy diagnose anything in need of overhaul, like bearing noise, worn brushes?

Nope, everything was good as far as he could tell without taking stuff apart. Just a lot of miles.