Wanted 1991 ST1100 OEM Alternator

[LuvMy91ST1100]

Hello,

The alternator outer housing cracked on my 1991 ST1100 with 86k miles. Does anyone have an OEM functioning take-off with the oring? I would even settle for just the outer case without the windings.
Mine was charging fine, it just leaked oil. The Honda part numbers are: "cover assy, alternator" 31130-MT3-003, and "O-Ring (95.5x2.4) (Hitachi), 91306-MS2-611.
I have no need or desire to perform the 40 amp upgrade. I just want to stop the oil leak and get back on to riding my wonderful ST.

Thank you in advance,
Tim

 

[Uncle Phil]

Tim - Since you will have to pull it, you might consider converting it to the newer 40 amper.
Probably not much more work and better in the long term.

 

[LuvMy91ST1100]

I already have it apart and the alternator cover assy off. I don't want to have to remove the air box and fuel tank. Plus having to purchase the drive gear case and air-cooled aternator. The alternator case (31133-MT3-003) would have to be replaced as well and mine will not come out without taking loose the engine mounts. It is a great deal more work and money to upgrade.

 

[SMSW]

It is a great deal more work and money to upgrade.

...you might consider converting it to the newer 40 amper. Probably not much more work and better in the long term.

Tim, it is your choice, but read what Phil wrote. He owns 8 1100's, 4 are for parts. He has swapped engines and probably done everything else you can think of on these bikes. Someone here has machined and made available the adapter plate. And there are guys who will talk you through the install.

 

[LuvMy91ST1100]

Thank you both for your feedback. It is very much appreciated.

Does anyone have an OEM alternator cover assy 31130-MT3-003, and "O-Ring (95.5x2.4) (Hitachi), 91306-MS2-611 they can part with?

 

[Uncle Phil]

I already have it apart and the alternator cover assy off. I don't want to have to remove the air box and fuel tank. Plus having to purchase the drive gear case and air-cooled aternator. The alternator case (31133-MT3-003) would have to be replaced as well and mine will not come out without taking loose the engine mounts. It is a great deal more work and money to upgrade.

I was presuming you already had the alternator out of the engine so you are halfway there.
Not trying to be a smart aleck, but removing the air box and the fuel tank are pretty easy.
The fuel tank (once it is reasonably empty) is only 4 10mm headed bolts - you just have to be sure and disconnect the sensor wire on the left side in about the middle of the frame 'V', the other 3 wires on top and the fuel line. Then you have all kinds of working room. I've pulled the fuel tank on the side of the road once because I had to -

Uncle Phil - West 2020 Day 07

The air box is just the top screws and then 6 in the bottom - but don't forget to reconnect the air hose that comes into the bottom of the air cleaner.
But it's not my circus and not my monkeys so you do what make sense for you!

You'll probably have better look just getting another complete 28 amper and either using it or doing a cover swap.

 

[Ron]

There seems to have been a post about that o ring a while back. There are not many to none left on earth.

edit

'93 1100 Alternator O-ring 91306-MS2-611 | ST1100-Alternator

Hey, all! After discovering and tracking down an oil leak on my 1993 ST1100, I'm trying to get some direction/advice on where to locate the Hitachi 91306-MS2-611 O-ring, which sets between the alternator cover and alternator case. All of my efforts have led to dead-ends with the words...

www.st-owners.com

Good luck.

 

[SMSW]

Tim, I assume you know all of the screws on the bike are JIS - Japanese Industrial Standard - and not Phillips. A phillips will damage a tight screw as it cams out of the cross slot while a JIS screw driver will hold tight. There are whole threads here discussing JIS screwdrivers. You can do a search using the search box (blue band, right end) at the top of this page.

A 1300 is very similar to the 1100. There are sufficient differences that some guys like one or the other, but keep it in the back of your mind when you finally part with your 1100.

 

[LuvMy91ST1100]

There seems to have been a post about that o ring a while back. There are not many to none left on earth.

edit

'93 1100 Alternator O-ring 91306-MS2-611 | ST1100-Alternator

Hey, all! After discovering and tracking down an oil leak on my 1993 ST1100, I'm trying to get some direction/advice on where to locate the Hitachi 91306-MS2-611 O-ring, which sets between the alternator cover and alternator case. All of my efforts have led to dead-ends with the words...

www.st-owners.com

Good luck.

Ron, I'm most likely going to use Right Stuff and make a seal/gasket. It works well sealing oil in and keeps its form under heat.

 

[LuvMy91ST1100]

I was presuming you already had the alternator out of the engine so you are halfway there.
Not trying to be a smart aleck, but removing the air box and the fuel tank are pretty easy.
The fuel tank (once it is reasonably empty) is only 4 10mm headed bolts - you just have to be sure and disconnect the sensor wire on the left side in about the middle of the frame 'V', the other 3 wires on top and the fuel line. Then you have all kinds of working room. I've pulled the fuel tank on the side of the road once because I had to -

Uncle Phil - West 2020 Day 07

The air box is just the top screws and then 6 in the bottom - but don't forget to reconnect the air hose that comes into the bottom of the air cleaner.
But it's not my circus and not my monkeys so you do what make sense for you!

You'll probably have better luck just getting another complete 28 amper and either using it or doing a cover swap.

Thanks Uncle Phil. The problem is If I take it further apart I WILL find other parts that I feel need to be replaced, and since I don't know the history of this MC I will be forced to replace the belt as well. I don't plan on keeping this MC for the rest of my life, only maybe a season or three. I have already had the carburetors off and replaced the coolant lines and water neck o-rings. It carburates well, gets 50mpg on a flat 50-mile cruise, and 46mpg through the mountains on a 230-mile ride. I'm hoping to find a late model low to moderate-mileage touring MC that suits my needs. That being said, it is hard to match, much less beat the features and capabilities of the 1991 ST1100.
Tim

 

[LuvMy91ST1100]

I greatly appreciate all of the experience and expertise of the owners on this forum. That being said I am simply looking to purchase an OEM alternator cover assy 31130-MT3-003, and "O-Ring (95.5x2.4) (Hitachi), 91306-MS2-611. I will be happy to also purchase the case cover on a defective winding assembly. The case on my alternator cracked and is leaking engine oil. The electrical part of my alternator is functioning as normal.

Thank you for your time,

Tim

 

[LuvMy91ST1100]

Tim - Since you will have to pull it, you might consider converting it to the newer 40 amper.
Probably not much more work and better in the long term.

Uncle Phil, is this the correct alternator for my 1991 ST1100A? If so, does split gear attach to this new one and fit right in the motor without an adapter plate? The engine has 4 bolts holding the OEM alternator in place. This alternator has 3 mounting lugs. Also, do you know of anyone who has the pigtail wiring I will need for the conversion?
Tim

Alternator for Honda ST1100 & ST1100A IR 12-Volt 40 Amp, 31100-MAJ-G41

Shop for the Alternator For Honda ST1100 & ST1100A IR; 12-Volt; 40 Amp, 31100-MAJ-G41 at DB Electrical. The best selection, low prices, fast shipping, and great customer service.

www.dbelectrical.com

 

[Uncle Phil]

The picture appears to be the one and they have the part number correct.
But you will need the adapter plate that I think someone sells on this forum.

For Sale - 40 amp New adapter plates for sale p/n 11202-maj-g20 | Buy/Sell/Wanted | ST-Owners.com

@John OoSTerhuis has a free loan kit that makes the job easier.
And here's an article on this site that will be helpful -

Article [11] - ST1100 - 40 amp Alternator Upgrade | ST1100 Articles | ST-Owners.com

 

[LuvMy91ST1100]

The picture appears to be the one and they have the part number correct.
But you will need the adapter plate that I think someone sells on this forum.

For Sale - 40 amp New adapter plates for sale p/n 11202-maj-g20 | Buy/Sell/Wanted | ST-Owners.com

@John OoSTerhuis has a free loan kit that makes the job easier.
And here's an article on this site that will be helpful -

Article [11] - ST1100 - 40 amp Alternator Upgrade | ST1100 Articles | ST-Owners.com

Thank you Uncle Phil.