Front sprocket nut loose, nothing new I know.., but....?

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RichUK
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Front sprocket nut loose, nothing new I know.., but....?

Postby RichUK » Mon Sep 04, 2017 7:11 pm

Do you guys loctite the sprocket splines? (not the nut, I mean the actual sprocket).

This is common fix for this issue on my trail bike (DRZ400).
They (on thumpertalk) figured out that is was being caused by the sprocket rocking on the splines when transitioning between powering and engine braking. If left unchecked a loose front sprocket nut could cause damage to the 2nd gear bushing as the output shaft needs to be torqued.
Is this the same on the SD990?

So on each sprocket install I degrease the output shaft splines, using loctite 270 (the permanent stuff) I put some blobs on the shaft splines before sliding the sprocket on. Since doing this I've never again had a loose sprocket nut on that bike (I did have before doing that btw).
The fix is that loctite fills the gaps and takes the small amount of backlash out of the sprocket, it shouldn't work but it does.

The only downsides are that if not careful the loctite will track back and glue in the spacer/collar that is behind the sprocket.
Also you then need a puller to get the sprocket off afterwards.

So, should I do this now?

Next the actual nut... I'm not impressed with it... the threads seem very shallow and have flat tops.
Is this normal or is this indicating a nut that has jumped somehow.
It still screws on fine but is very "jiggly" until there is some tension on it.
So is that normal or is mine worn out, or even worse has it jumped the threads, and thus come loose (if that is even possible)?

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RichUK
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Re: Front sprocket nut loose, nothing new I know.., but....?

Postby RichUK » Mon Sep 04, 2017 7:28 pm

I wonder if mine has been cross threaded sometime, hence the chewed up threads?

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Scotty
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Re: Front sprocket nut loose, nothing new I know.., but....?

Postby Scotty » Mon Sep 04, 2017 9:12 pm

Shouldn't it have a tab washer to prevent it coming undone? :shock:
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DaveNZ
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Re: Front sprocket nut loose, nothing new I know.., but....?

Postby DaveNZ » Tue Sep 05, 2017 4:43 am

RichUK wrote:I wonder if mine has been cross threaded sometime, hence the chewed up threads?

That nut looks cross threaded alright, time for a new one, and get a new washer that folds over the side of the nut to prevent it undoing, no need for lock tight, torque up the nut, the fold over the washer sides to lock in place. GET A NEW NUT AND WASHER!!
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RichUK
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Re: Front sprocket nut loose, nothing new I know.., but....?

Postby RichUK » Tue Sep 05, 2017 7:21 am

Scotty wrote:Shouldn't it have a tab washer to prevent it coming undone? :shock:


It does, and that washer is in ok condition.
It prevented the nut from undoing further, which is what it's job is. The washer alone isn't intended to stop the nut coming undone though, just to stop it from spinning all the way off.

DaveNZ wrote:GET A NEW NUT AND WASHER!!


WILL DO! :mrgreen:


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