Countershaft sprocket nut keeps loosening

[Guest]

Got a ?78 GS750 with a 530 conversion. Worked great until last week when the front sprocket loosened up a bit and caused a clunk when traveling at low speeds. Chain tension was at spec. I tightened the front sprocket up to 45 ft lbs again and it came loose in a few miles. I did it again today and installed a fresh sprocket washer and cleaned the threads with brake cleaner. The threads and splines look great. Made it further this time but I can hear the clunking starting again. What?s the next course of action? Loctite? I?m somewhat hesitant to put loctite on there since the FSM doesn?t call for it.

Matt

 

[cowboyup3371]

The washer that goes behind the sprocket acts like a lock nut when you fold up the tabs

 

[Guest]

The washer that goes behind the sprocket acts like a lock nut when you fold up the tabs

I’ve got the tabs bent down in two places. Sigh

 

[Agemax]

there was a whole thread about this a while back, use the search function and read through it.

 

[Steve]

I’ve got the tabs bent down in two places. Sigh

It has been a LONG time since I have even seen a countershaft sprocket, but isn't the washer between the nut and the sprocket?

Doesn't that mean that the tabs should be bent UP, to keep the nut from turning?

Maybe I just don't remember the setup correctly, but that's the way the brake disks are held on, too.

.

 

[Guest]

I?ve got the tabs bent down in two places. Sigh

The washer that goes behind the sprocket acts like a lock nut when you fold up the tabs

Correct if the washer has matching splines and it has been clocked to the nut, it shouldn't back off. Technically it's a lock washer.
WASHER, LOCK
09167-25019
Your Price: $2.95

Just an example photo to show the splines, you could use blue locktite which will hold the nut, but won't require using a torch to break it loose again. Whatever you do, don't use red locktite, that stuff breaks chitt if you don't torch it first.

 

[bwringer]

Yes, you need Loctite.

And more torque. Lots more torque.

45 foot-pounds seems to be in the ballpark of what the 10mm thread sprocket nuts on the back take, not the countershaft nut.

Just a guess with no manual on hand at the moment, but I bet the countershaft nut is supposed to get well over 100 foot-pounds. These are big, tough, hardened steel threads. Look up the correct spec and give 'em some added grunts.

Someone should be along soon with the correct torque value.

 

[Cipher]

72.5 -108.5 ft lbs 83 550
splines get worn if the thing is run loose
threads get damaged when folks force nut off without heating a loctited fastener

 

[Rob S.]

45 foot-pounds seems to be in the ballpark of what the 10mm thread sprocket nuts on the back take, not the countershaft nut.

Aren't those rear sprocket nuts held by "2-in-1" bendable tab locknuts? One piece of metal encompasses two locknuts with a span between them.

Between my '73 Z1 and '82 11E, at least one if not both uses this system.

 

[Cipher]

Aren't those rear sprocket nuts held by "2-in-1" bendable tab locknuts? One piece of metal encompasses two locknuts with a span between them.

Between my '73 Z1 and '82 11E, at least one if not both uses this system.

Splain please

 

[Cipher]

so im sure this setup is the same as my 550 a washer as gs rick showed and a nut that has a metal gripping insert on the threads

 

[Baatfam]

So this is a 530 conversion.
Silly question, but do you have the spacer on there, that comes with a 530 conversion?

 

[salty_monk]

The spacer goes on the outside of the sprocket. If it's a conversion sprocket the lump goes on the outside.

 

[RichDesmond]

Yes, you need Loctite.

And more torque. Lots more torque.

45 foot-pounds seems to be in the ballpark of what the 10mm thread sprocket nuts on the back take, not the countershaft nut.

Just a guess with no manual on hand at the moment, but I bet the countershaft nut is supposed to get well over 100 foot-pounds. These are big, tough, hardened steel threads. Look up the correct spec and give 'em some added grunts.

Someone should be along soon with the correct torque value.

Agree with this, mostly.
Blue locktite helps. Properly spec'd torque matters a lot too...

But, there's a nagging voice in my head that's going...45ft-lbs and no locktite isn't ideal, but it ought to hold for more than a week, especially if the lock washer is properly bent over. Having it loosen up three times that way is a real red flag. I don't have any idea what root cause might be, but I'd be looking at the whole system veeerrrry carefully.

 

[Cipher]

yeah as in the splines are buggered. Or the sprocket. You get a bit of rust from the hardening of the contact points between sprocket and spline I wonder if some high temp anti seize would help.

Also when torquing its be ideal to have a friend help as you need to be in low gear with the brake on or have the rear wheel otherwise immobilized to get it tightened properly.

Ultimately some pictures would tell of wonders but no one has access to a digital camera what with them being so rare.

 

[Guest]

45 foot pounds does seem low but it specifies 29-43.4 lb-ft of torque in the FSM for the GS550 and 1977-1979 GS750. I consulted the FSM for the Early GS1000 and it specifies a more realistic 65-72.5 lb-ft of torque. I’m tempted to try the higher torque value of the 1000 but it makes me somewhat nervous to deviate from the GS750 service manual but it also makes me nervous knowing the sprocket probably isn’t secured properly so I’m not riding it. I tried installing the 6mm and 1.5mm spacers when I did the initial conversion but the nut had pretty close to no bite on the countershaft. The 630 sprocket that was on my bike had the same width as the replacement 530 sprocket so I went like that. The old 630 sprocket also didn’t have the rubber dampers on it either and looking at the sprocket on the parts fiche it doesn’t have it either.. Very very confusing.

 

[Guest]

72.5 -108.5 ft lbs 83 550

The same on my 82 1100E, given as 100-150 N-m in the manual.


Mark

 

[Cipher]

are you using the OEM nut? Is it damaged in any way? I once had a nut completley loosen and it was only held on by the foam in the sprocket cover. It was ruined and it oddly only lightly damaged the threads.

Does anyone recall if the shaft is tapered at all? Tapered such that too thick a sprocket spacer combo would not allow the nut to seat properly and give a proper torque reading.

 

[Cipher]

I think FSM has an error or is referencing the reak sprocket nuts?
The char for a 10 mm diameter 7 stamped bolt maxes at 29-43.5 lb/ft
the shaft is a whole lot bigger than that

 

[RichDesmond]

I think FSM has an error or is referencing the reak sprocket nuts?
The char for a 10 mm diameter 7 stamped bolt maxes at 29-43.5 lb/ft
the shaft is a whole lot bigger than that

Wouldn't be the only time a Suzuki manual had bad torque values. Both the SVs and VStroms have examples.