Reinserting The Alternator Drive Gears Into The Engine

Uncle Phil

Uncle Phil

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Feb 26, 2007
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Age
73
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In The Holler West Of Nashville, Tennessee
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3 ST1100(s)
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In the process of removing the alternator from my 1997 ST1100 with 195,000+ miles on it, the alternator drive mechanism that the alternator goes into came out. Now I cannot get the drive inserted back into the engine so I can install the new alternator. I understand the process of removal that you should not do that and I tried not to. However, when something has been in place for 29 years and 195,000+ miles, things don't always go according to the 'manual'. Anybody ever done that and is there any solution to get the drive properly engaged without engine disassembly?
 
I upgraded the alternator a few months ago and discovered that the Lewis pin method is actually overkill for the job. I used a hex key (I don't remember the size) to engage the alternator drive gears while sliding it into place. I also had to put the gearbox in first gear and lock the driveshaft with a screwdriver. Here is the link to pictures: https://www.st-owners.com/forums/th...hope-chinesium-alternator.191360/post-2596216
 
Mine is the a 97 so it already had the 40mper in place. The issue is that it appears the only way to get the drive gears back in is to drop the oil pan (according to Clymer) which I would prefer not to do if I can avoid it. If the drive gears had not come out it would as simple as installing the new alternator (which I have done before).
 
Sure Iif you only need to remove alternator you don't need to remove alternator base plate. If I remember right, in the manual there is a note how to fix temporarily base plate to keep it on it's place while removing alternator
 
Alberto said:
Sure Iif you only need to remove alternator you don't need to remove alternator base plate. If I remember right, in the manual there is a note how to fix temporarily base plate to keep it on it's place while removing alternator
Click to expand...
Alberto - I already know all of that my friend as I have done a 40amper placement before. ;)
The issue is the alternator drive gear came out while I was trying to wrestle the old one out of place.
The old 40mper would not pry loose and when I applied lots of effort the drive gear came out unfortunately.
It appears you have to drop the oil pan to get the drive back in which I was trying to avoid.
That's why I am asking if anyone has come up with an alternative method. ;)
 
Alberto said:
No, I didn't drop the oil pan when installing the alternator gearing. I just drained the oil to avoid any spillage, and that was it.
Click to expand...
How did you do it then?
I've looked at your write up and I must have missed something (unless the engine internals are a bit different between 95 and earlier and 96 and later).
 
The easiest way is the lewis pin. You pull it out from the oil drain plug. You dont have to remove the oil pan. If you do it with the allen key as alberto says you could put it in gear and lock the rear brake.
 
Uncle Phil said:
How did you do it then?
Click to expand...
I put it in gear, and locked driveshaft to prevent the engine from turning over. then inserted alternator gear assembly (without alternator), engaged first thin gear, rotated gear a little with that allen tool inserted to splines where alternator goes to mesh main gear while pushing assembly further on it's place. Took 10 minutes. no hassle even with that lewis pin.
 
Alberto said:
I put it in gear, and locked driveshaft to prevent the engine from turning over. then inserted alternator gear assembly (without alternator), engaged first thin gear, rotated gear a little with that allen tool inserted to splines where alternator goes to mesh main gear while pushing assembly further on it's place. Took 10 minutes. no hassle even with that lewis pin.
Click to expand...
Oh, now I understand - you used the leverage of the allen tool to turn the drive enough to slide it on in!
I'm a little slow some days but now it sinks in. ;)
What size was that allen tool that you used?
 
Uncle Phil said:
What size was that allen tool that you used?
Click to expand...
Even a piece of broomstick, tip carved so it'll fit into the splined shaft bore, would to...
It doesn't require much force, nor movement, just a ~2mm twist/jerk to overcome the spring load and the gears almost "fall" into place...
The IMO more tricky part is to get the base lined up perfectly parallel and then overcome the friction by the O-ring when sliding it into the case...
I gave the O-ring and the case surface a smear with silicone grease and it went pretty smooth... methinks engine oil is a tad too runny for that process...
 
It appears that a 14mm is a shade too big (but AI says that is the size :biggrin:) but maybe a 13mm will work.
The solution is a whole lot better than dropping the exhaust so I can drop the oil pan ... ;)
 
Again you dont have to drop the oil pan. The lewis pin on a cable will come out the oil drain plug. Made one if you need it.
 
tnbill said:
Again you dont have to drop the oil pan. The lewis pin on a cable will come out the oil drain plug. Made one if you need it.
Click to expand...
Thanks for the offer.
I'll try the hex wrench first and if that doesn't work I'll give your lewis pin a whirl.
Right now I am waiting on new o-rings - no sense in going through this and not replacing them.
 
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