Rear Sprocket Bolt/Nut Stripped

[NotVeryCreative16]

So just as I've read about from other owners on several Yamaha forums, I managed to strip one of the rear sprocket nuts and/or bolts when torqueing it down even though I was only torqueing to 30 ft lbs. I'm not sure if this is because I should have been using new nuts or what. When I try to loosen the nut, it just spins. How do I get this off? I've never stripped a nut or bolt before so I really don't have any experience in handling it. If the bolt threads are stripped, I'll just replace the cush drive as I've found a 2014 and 2016 FZ-09 cush drive on eBay for about $30 and I'm sure that would be easier than dealing with changing out one of the bolts. I have a 2015 FJ-09. Would one of these fit?

[BBB]

I have a hazy memory that the sprocket bolt threads rotate if over torqued. If you can get to the back side of the sprocket you may be able to hold the bolt that way.

 

[NotVeryCreative16]

On 11/1/2020 at 4:46 AM, BBB said:

I have a hazy memory that the sprocket bolt threads rotate if over torqued. If you can get to the back side of the sprocket you may be able to hold the bolt that way.

The bolt isn't rotating though, just the nut. I marked the bolt to make sure.

[skipperT]

Hopefully you figured out a solution by now, but to answer your other question, those nuts are supposed to be replaced. They will only hit the 70nm figure once, the first time they are used. 

otherwise, you could cheat and use a slightly lower torque next time with a dab of blue loctite. 

HTH someone, 

-Skip

[peteinpa]

Just looked in my service manual and sprocket nuts don't say replace at every removal. 

The tourqe spec of 58 ft. lbs. is just crazy high as usual. They will be fine at 25-30 ft. lbs. 

If you do strip them they are studs in the rear alluminum hub. Will get costly fast.

[skipperT]

58 ft lbs is not “crazy high” if a new fastener is used. You are right that the book doesn’t say “must replace” but in my experience, 10 bucks for new nuts and the correct torque value is cheap piece of mind.

25-30 is WAY to little for such a critical fastener and NOT good advice, IMHO. Just because you can calculate a recommendation based on the measurement of the fastener “flats” doesn’t mean that it should be used. Yamaha actually says that in their books as a matter of fact, that using a value based on fastener measurement should NOT be used if the fastener is specifically listed in the Chassis and Engine fastener torque charts. 

-Skip

[peteinpa]

If you're going to renew anything then change out the studs. The nuts don't go through any change with use but the studs may stretch.

There are 6 holding on a sprocket. the force is not trying to pull off the sprocket but rotate it. They are lock nuts, where are they going to go? 

All my first bikes were Hondas. Never any problems with any fasteners or the called out for torque with a LOT of wrenching. It started with my first Yamaha, my FZ-07. Everyone was stripping their rear axle with the crazy torque called out for it of 76 ft. lbs. 108 ft. lbs. for the FJ-09 rear axle nut, REALLY? My ST1300 was 80 ft. lbs. It too was a lock nut. I never had a problem with the same nut and axle with all the tire changes.

I had a CBR1100XX before my ST1300. I did ALL my own work on it following torque specs in the manual. 80K miles worth of tires, chains, sprockets, brakes, etc. Same axle, nut, sprocket nuts, etc. I routinely took this bike to 150 mph and more in my (irresponsible) youth. (69 ft. lbs. for its rear axle nut BTW)

Something is wrong at Yamaha. Their lawyers would rather have you destroy parts than "maybe" have a nut fall off. In destroying threads, isn't that part compromised and thus not safe?

Maybe it's inferior metallurgy. The parts can't handle the called for torque.

I love this bike. Honda has lost it's way with its current and earlier offerings. Nothing turns me on.  I'm going to have to adapt. With every bolt/nut I torque, I will decide what it gets tightened to based on if it goes into aluminum, what its job is, etc.  

[bwringer]

Weird how the manual for this bike is full of ridonkulous torque values like this.

Just replaced the chain and sprockets on my 2015 (and yes, I used new OEM nuts as specified in the manual) and 70nm (58 foot-pounds) is just plain nuts. I have no doubt one or more of the studs would have stripped at full torque.

I stopped at the spec used by Suzuki for my V-Strom DL1000, which is 60nm (44.25 foot-pounds). That was very, very damn tight, and I have absolutely zero concern.

This seems to be a thing on every bike I've owned; somewhere in the manual is a ridiculous torque spec or some other error that will break stuff if you blindly follow it. This bike has its share, that's for sure.

And no, I definitely did not tighten the rear axle nut to 108 foot-pounds...

The front sprocket nut did get a new nut and the shockingly reasonable torque as called for in the manual; in looking at that wee sprocket nut it's obvious that it's a one-time item. Very fine threads and not a lot of material, not to mention it's staked into place. Not what I would have designed, but it seems to work well enough.