Final Drive Findings

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Brly

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I don't know if anyone will remember, but I made a post a little while ago about my drive chain suddenly rubbing the inner primary case. I guessed that the gearbox had shifted in the cradle just enough to make the chain come into contact with the cover. Well, I guessed wrong...
I took the outer primary cover off and pieces of chewed up metal and chunks of felt seal came out with the ATF, not what I was expecting. A quick look over everything showed no damaged to the inner primary workings. Once everything was gutted and I took the inner cover off, here's what I found.
Final Drive Findings

Final Drive Findings

The screw that threads into the sprocket and holds the lock washer on had come out. The washer came off, the nut unscrewed and the sprocket was just floating on the shaft. I assumed the splines and threads had been damaged on the shaft, but luckly, everything went right back together. The new sprocket I had came with a new allen head screw. I tried the new screw in the old sprocket and both holes were loose on the screw.
I'm sure if I had ridden it like this, there would have been damage, but I don't think there would have been any catastrophic damage. I don't think the sprocket could have come off the shaft. The drive chain is relatively new and doesn't have the sideways flex like a worn out chain does. Even if the sprocket came off the shaft, the motor would have spun but nothing would've been tranferred to the wheel. I put the new sprocket on, this time using loctite on the sprocket screw, and I really buried it. Three of the clutch plates were really (!) stuck. I cleaned them all and put everything back together. On the first test ride, it went into first gear so quietly and easily that I wasn't sure if it even went it. It has never shifted to easily. It's definitely running and functioning the best is has since I've owned it. Went for a 60 mile ride Monday morning, and it was soo nice.
So, everything came out ok. I intentionally got a 20 tooth sprocket to try out, assuming that I currently had a 19 tooth. Wrong again. The existing sprocket was a 20 tooth already. Oh well, at least the sprocket is new...

Ben
 
Now that's a new one on me, thanks for going to the trouble to demo this mode of failure. Did you replace the inner cover and seal? As you found out the big nut don't have to be that snug to do its duty, so the little lock screw in new lock ring is only thing I tighten good down there with some blue loctite. AMC tranny may be the sweetest operator ever sold. Can't wait to read you next surprise riding around on unknown Cdo that you ain't gone through soup to nuts yourself, or paid hi dollar for one that was by honest skilled builder. Every ride I take I have to emotionally balance out my feeling of faith vs forced on fate.
 
Yeah, it was a suprise to me. I actually did tear this bike down to the frame and put it back together. I know I didn't loctite the sprocket screw in when I put it back together during rebuild (I know, shame on me), but I believe there was something amiss with the threads in the sprocket. Since the rebuild, I've only put about 2,000 miles on, so it held together for that long. I'm not sure what made the screw back out when it did. The inner primary cover was not damaged, just the thin washer that you see in the photo and the felt seal. Everything is sealed up nicely now, no leaks after the ride.
Something I found interesting was when I put the stator back on over the rotor, I didn't have the correct gap between the stator and rotor. I tweaked the stator mounting studs until I got the clearance all around, but how would that have moved? I know I put it back on the way it came off, i.e. with the wire leads coming off the stator at 5 o'clock.

Ben
 
Ugh Ben, forgive my bad ass-sumption you just hopped on and took chances with a already runner like me for even more work than if I'd soup to nut'd it in mature discipline. The more I'm around Commandos the stupider I feel and the stranger they get. Likely the retainer screw holes was buggered just enough to fool ya the screw was in well enough so no way to avoid but leaving it parked. Due too Cdo's I now believe in Shoe Eves, just like ET's, by the trouble they cause when we are asleep, ET's are like pirates snatching folks out of bed and Shoe Eves are the Devils little helpers. As you found out its meanish brutal to tweak the stator studs, so how in the mysterious world could they get off if prior were fine. As our families generally could care less, its forums like this that prevent sucides and bike murders in raging insanity. [at least for unstable's like hobot - ET's snatched and replaced mind implant long ago] Enjoy your fully fettered Commando and don't think about what could happen next time away.
 
Whoa ,looks to this dude like the chamferred side of the big sprocket nut might be facing outwards ,not towards/facing the sprocket itself ? Or it could be wear where the nut ate into the plate ? Which is it. Look at this as an opportunity to fit a better plate with a modern seal instead of felt. No big damage .Good.
 
Loctite #222 on every small screw helps. Do you have the special socket to allow reaching full torque on the nut?
 
Torontonian - I probably took it off and put it back on before I snapped the picture and didn't pay attention to the chamfered side. It's on correctly now.
Concours - Loctite use is noted. No special socket. It's TIGHT.

Ben
 
O.K. ,we all know the chamferred side goes towards box ,right ? Or yes there is a danger of the huge nut backing off. In my younger days all we had was big vicegrips adjusted to max and a 5 Lb. sledge to hit until it popped off. Nowadays I took the nut to a friend's shop ,he cut pieces to weld into a deep reach tool to accomodate the mainshaft protruding. It has a welded on bar to strike with guess what ... a 5 Lb. sledge !
 
Brly said:
Torontonian - I probably took it off and put it back on before I snapped the picture and didn't pay attention to the chamfered side. It's on correctly now.
Concours - Loctite use is noted. No special socket. It's TIGHT.

Ben
Click to expand...

Do tell, HOW to get it it tight without a 6 point, modified extra deep, ground flush and O.D. reduced socket? :?:
 
Basically he fit the six rectangular cut pieces of metal around that nut , then spot welded in place ,then welded it up. So both ends of this "tube" are completely open. A steel bar for smacking tight was welded to the mechanic's end. I'll try to get a friend to help posting a picture ,a tad busy now gardening work. Enjoy.
 
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