My 1970-ish ratchet 4-speed electric/kick transmission main shaft sprocket locks up as I tighten it's nut. It was tuning freely a moment ago, until I torqued it to 50-60ftlbs.

I recently picked up a pretty neat 1970-ish Shovelhead Electra Glide sidecar rig, not running. I've now gone through it and have it running well, but have not yet driven it - changing the transmission gear oil revealed a big oil leak at the mainshaft sprocket (front drive chain sprocket), so I tore it open to replace the seal.
When I was disassembling it all I noticed the sprocket was slightly wobbly lose on the shaft, and the shaft spun freely. I would say the sprocket nut was slightly more than finger tight and retained with the lockwasher.

After replacing the seal behind the sprocket, (please assume I did this correctly, with both the 'main drive gear spacer,' alignment clip, shaft seal (seal is a new James double lip), and the sprocket are all installed correctly and not backwards), the sprocket spins freely when the nut is finger tight. But as soon as I start to tighten it the sprocket starts to seize. The sprocket is not touching the transmission. I can't see what is making it seize. Again, the sprocket was lose on the shaft pre-disassembly, and now I suspect this was intentional by the previous mechanic. Note, the photo is from before I cleaned things.

The inner shaft has effectively no lateral free play, and the outer shaft that the sprocket rides on has about 0.0800"/2mm of free play.

I am not sure what is happening, but I suspect it might have something to do with a missing thrust washer that is possibly inside the transmission, which is something I really really really don't want to hear. My current best guess is that #6 in the workshop book may be missing -- is there any way to inspect this without pulling the tranny? Can this be inspected if I carefully remove the 44(?) roller bearings? Otherwise, everything that I know how to visually inspected appears to be correct.

I thought the bike was going to finally be ready for it's first test drive this afternoon until I found this problem.
I am a reasonably experienced vintage bike mechanic with over 30 years of experience, but this is my first old Harley.

Thanks for any thoughts!

 

At this point pulling the gearbox and doing this on the bench is a better option. These are not difficult to work on.

If it worked before you did the seal and not after, you messed up. Time to backtrack and start from square one. You have a shop manual, right?
Pull the lid off and start checking your tolerances on the main shaft, you can also visually confirm at that point the shims and washers are in place.

Get back with your findings.

 

BTW, killer rig!

 

IIRC #6 only sets endplay on the main drive gear. It could be too thick but I doubt it's the issue. I'd suspect that #10 is worn down and the sprocket is rubbing the case. If not that then I suspect something inside the tranny is damaged. Pulling a sidecar definitely puts more load on the tranny.

 

Well, I must have been born lucky, because I found the problem on my first try.

My suspicion was right on the money that the #6 thrust washer, OEM part number 35131-36, was completely missing from the transmission. These come in different precision thicknesses to ensure lateral end play. Because mine was missing it allowed the 4th gear to rub against the inside wall of the transmission housing. If the chain drive sprocket was left loose the gear wouldn't rub, or would only just barely rub. If the sprocket is correctly torqued it jams the 4th gear against the wall so hard that the transmission locked up. This explains why the previous owner/mechanic left the sprocket finger tight. I am very fortunate all these parts are not destroyed from the neglect. I suspect this was one of the reasons the bike was parked. Another was a major oil leak, but the engine crankcase breather was plugged! Of course it would leak... I've sorted all that out now, verified oil pressure at the heads, and I think it might not have any significant oil leakage.

I am proud to have sorted this out, to have removed the transmission, disassembled it, and verified the issue without breaking anything, and managed to do it all in an afternoon.
I ordered the washer, a transmission seal set, a quart of gear oil, plus a replacement sprocket gasket as I had to destroy my newly installed one while diagnosing this mess.
I need to order transmission oil. WHAT OIL SHOULD I USE???!! Just kidding. Please don't tell me what oil to use.
I bought all the parts through J&P Cycle. Does anyone recommend a better retailer for this stuff?

If anyone cares, a bit more about the back story of this bike, I purchased it from a family after the owner passed away. It was much loved and the previous owner was quite a character and a pretty cool guy. They did not want to sell me a motorcycle. They wanted me to receive a story, and to carry it on for them... The bike has been sitting for maybe about 15 or 20 years. It was parked because the owner was getting old and it had "a short list of issues..." The short list basically meant that every single system had to be gone through, from the front drum brakes to the pogo seat springs, everything was needing a lot of love. I have been fraying the edges of my shop manual and systemically working my way through it all. I've been a bike mechanic for over 30 years, but this is my first Harley... So I am kind of a very experienced noob.

When the transmission parts arrive it should finally be ready for its maiden voyage/first test ride around the block. Once it seems to be safe, mostly sorted and somewhat reliable, then I'll attach the sidecar and see how all that works. The side car has a drum brake that shares the bike's rear disc hydraulics.





Something is missing from this motorcycle.



That darn 3rd gear retaining clip was put there by the devil.



There is some minor visible scoring around the edge of the 4thy gear. For the sprocket installed only finger tight the splines are in surprisingly good shape. I ordered a "Super Nut" for when I reinstall all this stuff.

 

So you had the spacer?

 

No. I have to order one. I was sold the bike with the thrust washer missing.

 

Are you sure the spacer isn't there.. Looks like it is.

 

I had a 1968 factory rig with 3speed/reverse. Same juice sidecar brake. After having the drums cut and bedding the shoes the bike stopped fine. With the sidecar drum in the rear circuit, i had to install a portioning valve. Otherwise it was too sensitive to input. Ultimately i just shut it off. The bike was more than capable of stopping fine with just the bikes brakes.
FYI, if you grab a handful going forward you can lift the rear wheel unless you have over 100 lbs in the car.
We won peoples choice!

 

Thank you for this great question. No, the spacer is not visible in the photo of the main shaft 4th gear, but after you asked I went back and found it jammed in the '44 roller bearing housing.' Both the gear, the washer and the bearing appear to have some wear, and now I am trying to sort this out. I'd prefer not to spend $200 - $300 just buying and replacing parts if I don't need to buy them all.

The Main shaft seems to be in good shape with 0.002" of wear near the 4th gear's inner Main shaft seal (with no gouging or scratches). the 4th gear's bushing seems to be good, with maybe 0.001 or 0.002 of wiggle on the shaft - basically none, so the shaft and bushing should be good.

So now I am trying to figure out why the 4th gear had about 0.082" of lateral (in and out) free play on the shaft. Obviously parts are worn out - but as an inexperienced Harley mechanic I don't have a strong sense of whether this is a common failure, or perhaps there is something clever that needs to be attended to that only an old school knowledgeable guy would know to inspect as a root cause...

Here are a couple more photos of the transmission housing with the thrust washer in there, first from the outside, then from the inside. I just disassembled this last night, then went to bed, so I haven't cleaned anything yet.







1972 Harley transmission mainshaft and housing



1972 Harley Transmission countershaft and housing




Mainshaft



4th gear with galling at the thrust washer mating surface. It appears the recessed area. Note only the inner race was rubbing. I believe the recessed area and the outer ring around the gear teeth are just rough cut and have not been making contact with anything.



the 0.060 stock thrust washer is heavily galled.



The inside of the bearing race has a tiny amount of a raised lip, but I think this can be corrected with a small file and emery cloth. It otherwise looks good.


The thrust washer bearing was clearly rubbing against the inside of the lip here. The 4th gear and thrust washer show also show visible wear.