Countershaft sprocket nut keeps loosening

[mattd1205]

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.

[mmattockx]

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.

[bwringer]

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.

Exactly what I was thinking. These are hardened steel on steel threads. 43.5 foot-pounds makes not the slightest sense at all.

Not sure of the thread size on this application, but the usual specs for, say, 16mm threads (that's on the low end; countershaft threads are almost definitely bigger) are usually between 180 and 247 foot-pounds depending on fastener grade you're assuming.
https://www.boltdepot.com/fastener-i...ed-Torque.aspx (No idea why this chart is in NM.)


Maximums can be even higher, depending on grade, desired bolt stretch, etc.:

https://www.engineeringtoolbox.com/metric-bolts-maximum-torque-d_2054.html

NM to foot-pound converter:

https://www.theunitconverter.com/newton-meter-to-foot-pound-conversion/

In any case, it's quite clear that 43 foot-pounds isn't even near the ballpark.


And yes, I'm sorry to say that the revered FSMs for vintage and modern Suzukis are chock full of egregious errors like this and should never be followed blindly; the many errors in FSM torque specs especially have caused no end of angst and misery... always engage brain before arm.



If the issue continues after proper torquing, the PO would do well to remove the sprocket if possible and examine the splines for excessive wear that might be allowing the sprocket to "work" back and forth.

[Gorminrider]

'round about 35-50 ft/lbs is common for this nut across several manuals for several brands of bikes I have.

Something else is happening.
There's teeth on the shaft/sprocket interface so what could work to loosen a nut excepting not having the sprocket on all the way and tightening it?

Perhaps it's turned round the wrong way before sliding onto the shaft if there's a difference.

[Baatfam]

Pictures would help.....

[Cipher]

oh but for a picture of the shaft and sprocket dismantled.................

[allojohn]

oh but for a picture of the shaft and sprocket dismantled.................

+1, that might clear this up instantly....

[Rob S.]

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

This pic any help (GS1100E)?

image.jpg

[Cipher]

This pic any help (GS1100E)?

[ATTACH=CONFIG]59122[/ATTACH]

AWESOME i think the brave new world of digital photos will save us all

[mattd1205]

Well, I’m back ha. It loosened up again. I tried 65 pound feet of torque this time. Same thing here are some pics of my output shaft. Are the splines excessively worn?

[rphillips]

I know, everyone loves Clymer manuals, but I had one in the garage for the Suzuki GS 750's, & dug it out. It says Drive sprocket nut, 1979 & earlier, 29.0 to 43.4 ft. lb. TSCC models 65.0 to72.5 ft. lb. Don't seem right, but that's what it says. Also says there is a recess on one side of the nut, the recess goes to the inside, against the sprocket.

[mattd1205]

I know, everyone loves Clymer manuals, but I had one in the garage for the Suzuki GS 750's, & dug it out. It says Drive sprocket nut, 1979 & earlier, 29.0 to 43.4 ft. lb. TSCC models 65.0 to72.5 ft. lb. Don't seem right, but that's what it says. Also says there is a recess on one side of the nut, the recess goes to the inside, against the sprocket.

if anything it took less time to loosen up at the higher torque. I have the recessed portion of the but facing in. The threads aren’t boogered up either. This is a real head scratcher.