Cracked clutch nut? Gearbox removal on 71?

I pulled the primary cover in preparation for removing the gearbox on my 71 750 tonight, had to quit for a beer at the engine sprocket when I couldn't find the long bolts for my puller. Another victim of the move.

Anyway, couple I got the clutch center nut off, but noticed it looks cracked, pic below. And if there's supposed to be a tab washer behind it, there wasn't, looked like a lock washer. It was holding fine, no slop in the basket, but I'm assuming that's a replacement. Any other wear areas I should pay close attention to? I also found that the left footpeg bolt studs came out with the bolts and look slightly bent, hopefully I can find a new set of those and loctite them in.

And, just to confirm - I've read through a few older threads here. I think what I gathered is, you can pull the gearbox on the 71 without moving the engine, if you remove everything on the primary side, 3 rear engine bolts, and the top and bottom gearbox bolts/studs, and rotate the gearbox backwards for clearance. Do I have that right?

Yeah, that nut is split in half. Buy a lottery ticket. Also, the published torque value for that nut is erroneous, the circlip behind the hub deforms. 45 ft. lbs. is the tribal knowledge value.

Make sure you use the proper lock tab when your rebuild that,. because they are parallel splines, the only time they would have been a firm fit was when the bike was new but I doubt that. Because of the free play between the splines the hub will always move on the shaft and will always com loose, even with a lock tab because of the oscillations between hub and shaft.
Also, make sure the nut on the other end of this shaft is well loctited because there is no other way of locking it to the shaft. They come loose and fill the box with iron paste when the nut turns into a bush.
Dereck

Nortim said:

Anyway, couple I got the clutch center nut off, but noticed it looks cracked......... And if there's supposed to be a tab washer behind it, there wasn't, looked like a lock washer.

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The lock washer 040374, and no tab washer would be correct for '71 as the tab washer 063459 and (hardened?) flat washer 063447 were supposedly fitted from 208945, so somewhere around mid '72.

https://andover-norton.co.uk/en/shop-dr ... alternator

https://andover-norton.co.uk/en/shop-dr ... lternator#

I have read on here that some owners believe tje yab washer its self can cause the nut to come loose as by its nature it is made of soft material that is deformed overtime as the clutch is put under load. This then leads to the nut losing torque as the washer is crushed thinner thus creating more movement and the washer is crushed further an so on an so on.

Many therefore recommend not fitting the washer but using loctite or locking wire instead. If you choose these methods ensure your nut does bit down on the clutch centre now the washer is not there to bridge the gap (this may depend on the amount of shims on circlip side of clutch centre). I have have issue but it is simply a matter of using two of the harden type washers not just one under the nut (in my case anyway). I also use loctite and locking wire (belt and braces) which is threaded through the existing holes in the clutch centre and two i drilled through opposite sides of the nut (i wanted to try not to effect the balance by just doing just one side but thats just me).

I have a new clutch (fitted belt drive) and mainshaft (worn original in sleeve gear area) and they are a good close fit and do not come loose but if your clutch centre or shaft are worn then maybe you should consider replacing them if you wish of course. As the saying goes you pays your money so you takes your choice.

Thanks all. I will inspect the clutch center and shaft for wear and replace as needed. The sprockets and primary chain themselves look in great shape, very little wear.

Is it better to use the lock washer and nut that came on the 71, or switch to the later tab washer/hardened washer and nut, as on the later bikes? I generally loctite every fastener I particularly want to stay fastened, but will look at safety wire as well.

jim comstock (comnoz ) on here sells a belville washer to replace the lock washer or flat washer and tab. IMHO it is a far better way to go. the lock tab as stated is soft and has been known to work loose.

Bugger, I forgot to mention I put in a larger hardened washer as well.
Dereck

Gearbox out, time to clean and inspect. One of you guys sure could've reminded me the sprocket nut was LH thread though :lol:.

I've found Belleville washers at Fastenal before, will see if my local shop has them.

Dude, we're all old... we forget too :mrgreen:

Bugger, forgot to mention the sprocket nut is left hand thread. [ And that is because i couldn't remember ] I AGREE WITH CONCOURS

Dereck

Come on, there are things your need to workout for yourself.

bill said:

jim comstock (comnoz ) on here sells a belville washer to replace the lock washer or flat washer and tab. IMHO it is a far better way to go. the lock tab as stated is soft and has been known to work loose.

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+1, the tab washer on my bike compressed over time and this caused the nut to become loose. FWIW the belleville washer alone didn't lock the nut and it loosened after maybe a few hundred miles...however I then cleaned the threads and applied blue threadlocker, that combined with the belleville washer has done the trick for a few years now.

also it has a champhor on one side that goes to sprocket side.
+1 on lock tight on BOTH ends of the main shaft.

Nortim said:

One of you guys sure could've reminded me the sprocket nut was LH thread though :lol:.

.

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Just kidding of course, doing my research I read about that LH nut at least once, just didn't stick.

Next question: I was originally planning to buy a whole gearbox refurb kit from Andover - all bearings bushings, etc. But now that it's apart, I wonder if that's overkill. The bike only has 13k on it, the main bearing looks good and feels smooth, and the bushings aren't too worn, still a pretty tight fit. All the gearbox internals look good to me. Worth just doing a new layshaft bearing, gaskets, and o-rings, and save some cash for other stuff, or is that false economy?

Nortim said:

Just kidding of course, doing my research I read about that LH nut at least once, just didn't stick.

Next question: I was originally planning to buy a whole gearbox refurb kit from Andover - all bearings bushings, etc. But now that it's apart, I wonder if that's overkill. The bike only has 13k on it, the main bearing looks good and feels smooth, and the bushings aren't too worn, still a pretty tight fit. All the gearbox internals look good to me. Worth just doing a new layshaft bearing, gaskets, and o-rings, and save some cash for other stuff, or is that false economy?

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The latter, pre-emptive layshaft bearing and inspect everything.
If you choose roller bearing, be prepared to shim the kicker shaft.

concours said:

The latter, pre-emptive layshaft bearing and inspect everything.
If you choose roller bearing, be prepared to shim the kicker shaft.

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Not pre-emptive - layshaft bearing failed on the PO's last ride, he stopped when it got hard to shift. Luckily so, as the inner race was in pieces when I pulled it out. With one end of the layshaft walking around I expected to find more damage inside, fairly surprised. A bit of fine metal, likely from ground-up bearing race chunks, a few metal flakes.

Nortim said:

..... - layshaft bearing failed on the PO's last ride, he stopped when it got hard to shift. Luckily so, as the inner race was in pieces when I pulled it out. With one end of the layshaft walking around I expected to find more damage inside, fairly surprised. A bit of fine metal, likely from ground-up bearing race chunks, a few metal flakes.

Click to expand...

Wow that was lucky

"Worth just doing a new layshaft bearing, gaskets, and o-rings, and save some cash for other stuff, or is that false economy?"
As long as you're in there, you may as well install some new bushings, as they are not very expensive.
FWIW, I have 3 times the mileage on my gearbox, and only the layshaft bearing has given trouble. Be advised that the GB "sweats" a lot. A tiny hole drilled in the inspection cover is often recommended, and frequent gear oil changes will pay off in the long run. Again FWIW, I've had good results with a synthetic called Redline Heavy Shockproof.

Some of the bushings I got were looser than the old ones. Food for thought :idea:

The tiny hole is there from the factory. It can be cleaned.... prob full of Simichrome.

I would replace the sleeve gear bushings too.