Sprocket Nut Focced

[Timbollew]

Hey people, so my rear hugger was knackered and a chunk had cracked off and gone forwards towards the sprocket housing, no bilgy whipped the hugger off and removed the broken bit from the housing. I thought I'd bester remove the sprocket cover to check that no little bits had gone into it. This is where it gets interesting, since I've had the bike I've had no reason to remove the sprocket housing and so I was interested to see what the sprocket but would look like having read that they're problematic. The sprocket nut just spun around I literally just pulled it off the spindle, there is no thread whatsoever on the nut and I can see a rub mark on the inside of the cover where it has been rubbing. So the only thing holding mine chain on was the thickness of the nut against the sprocket cover  .


I'm not gonna ride it until I've got a nut on here and I'm gonna take the opportunity to replace the chain and sprockets. I'm worried now though because there is not thread on this nut and I'm thinking has the previous owner had a problem with it and just chucked on a bigger nut and reamed the inside out. I've got some photos, do you think it's possible for the spindle to wear the inside out this cleanly? There is thread on the spindle but I hope the new nut will go on OK.

[red98]

That must have been rattling around inside the housing , loose, for a fair while to smooth it out like that  ......looks like a spacer  ........hope the shaft thread is not damaged....got a picture of the shaft ?

[Timbollew]

I know that's what's got me worried as to whether it had a thread or if it's been machined out as a temporary fix. Surely nobody would do that though. I'll get a pic of the shaft a bit later. I'm hoping the thread is OK, I'm assuming it's big job to replace.

Where's the best place to get the upgraded nut?

[Buzz]

Dealer should be able to sort you one for about £3, failing that get one from Wemoto for about £8 inc Del.

Whatever you get make sure that it's not the original 9mm one but the 12mm nut with part number 90891-10124, like the one you get from Wemoto.  Not a big job but you'll need a 32mm socket, and a torque wrench setting of 90 Nm, check the manual for the exact setting (I think the original spec was 70 Nm for the 9mm nut but I think it was upgraded to 90 Nm for the 12mm nut)

[Soapy]

It's really weird how this effects some bikes and not others. I have a 03 Foxeye which only has 4000 miles on it. I never had any issues with vibes or rattles in that area. But I thought I'd better check it out after all the reports on here. Well for the sake of a few quid I thought I'd have the 12mm replacement to hand.


When I removed the cover, the nut was the original 9mm with no signs of any movement. Decided to change it anyway and Lo and Behold I needed assistance and a 3 foot breaker bar to crack the old nut off.


New one fitted and torqued up to 70 Nm, didn't realise the new 12mm needs 90Nm, Thanks for that info Buzz. I'll go back and redo that.

[Buzz]

New one fitted and torqued up to 70 Nm, didn't realise the new 12mm needs 90Nm, Thanks for that info Buzz. I'll go back and redo that.

I've had a quick search for what sparked that memory and came up with this http://foc-u.co.uk/index.php/topic,2449.msg19941.html#msg19941 Mine is at 80 and has held for the last 2 years.  I can't find any concrete evidence for 90 Nm but that doesn't mean to say it won't take it.

[limax2]

This has been greatly discussed on here in the past and below is a drawing I did some time ago.
The original Yamaha inspection notice said if the outside diameter of the shaft thread was more than 17.5mm, replace the 9mm nut with the new 12mm nut. If thread less than 17.5mm shaft to be replaced. The ones I have measured have always been round the 17.85 mark, so classed as O.K.
Under sized shaft threads was given as the reason for the nuts coming loose. I suspect in "some" cases it could have been incorrect assembly after fitting a new sprocket.

Details

When I spoke to Yamaha back then they said to torque the new nut to 90Nm. I believe there was a service note 2005-12A stating this but I have never seen it myself.
Final point don't forget to use loctite on the thread. That is part of the reason why a nut can be very tight to undo and not because it was done up that tight on assembly. (Unless it has already come loose of course!)

[unfazed]

I posted my solution to the problem when I ended up with 2 threads left on the shaft and it is still working 9500 miles later
See this link How I fixed my Sprocket nut problem

It has been viewed over 800 times and downloaded over 500 times but nobody ever came back to tell me they tried it.

[savvy]

No pics but to make sure on mine I bought a new nut, drilled and tapped a 4mm thread from one of the flats on the nut and into the centre threaded hole,I then obtained a couple of 4mm grub screws (good ones as they are toughened) and tightened one against the shaft with the second one tightened against the first.
 Has worked so far.
 the local cycle shop supplied the 4mm taps.

[Sannox]

My sprocket nut and washer have probably screwed up some French farm machinery as they both pinged off into a field at 110mph not far from St Quentin back in 2011, the local Yamaha shop did a nice job picking the bike up and fitting a temp nut as a get you home fix, a trip to my local Yam dealer where I bought the bike yielded a ' Don't know nothin' about that problem, sniff' and £6 lighter and the proper replacement thicker nut, no problems since I fitted it and I check it, a lot, quite a lot :-)

[unfazed]

No pics but to make sure on mine I bought a new nut, drilled and tapped a 4mm thread from one of the flats on the nut and into the centre threaded hole,I then obtained a couple of 4mm grub screws (good ones as they are toughened) and tightened one against the shaft with the second one tightened against the first.
 Has worked so far.
 the local cycle shop supplied the 4mm taps.

A very effective method of keeping the nut in place if you  have enough threads left to tighten the nut fully. I could not risk the full torque with two threads. I had seen something like it on a few Suzukis
However Yamaha Ireland supplied all the parts needed to strip and replace the shaft for half price. I could not complain really as the bike had covered 72000 miles

[Paul]

I haven't had this problem...yet.


However if I did, I would:


1) Grind off the lip of the nut so that when it tightened up it locked on the shaft before exerting any pressure on the sprocket and washer.


2) Use 'bearing fit' or similar on the threads when I tightened it up.


The nut is there to hold the sprocket in position, it doesn't really need to be tight against.


The old Hondas used to have a similar arrangement if memory serves.

[Timbollew]

I'm hoping I'll be alright as the thread looks OK. Won't know really until I screw the new one on, hopefully this weekend.

As I said I'm gonna take the oppurtunity to do the chain and sprockets.  I don't have a riveting tool, any recommendations? I was looking at this as I don't wanna spend a fortune http://www.ebay.co.uk/itm/161226315310 . Any tips for fitting chain and sprockets?

[His Dudeness]

I think taking the swing arm off and using a continous chain is probably easier than buying a riveter and riviting the chain and you can grease your swing arm bearings

[Timbollew]

I've already ordered the split chain now

[His Dudeness]

   the split chains add an extra 5hp so you made the right decision

[Timbollew]

Well that's good chuck in the fact it's silver and I don't reckon even Rossi can catch me.

[unfazed]

That because Rossi is on a slow blue Yamaha 

[Timbollew]

The good news is the threads fine. Fitted the nut and tightened to 80nm for now. Waiting for chain and sprockets to come