Author Topic: sprocket nut (Read 11886 times)

snakeyprince83 · « **on:** 13 July 2015, 12:22:49 am »

Hi guys, i have recently heard about the problem with the sprocket nut not fititng properly and falling out, i have an old 98 fazer, 4'600 miles, i'm a bit paranoid now and want to go check it out, what am i looking for?, is it easy to check myself or would taking it to the garage be the best bet? Cheers.

darrsi · « **Reply #1 on:** 13 July 2015, 06:46:19 am »

Get a torch and point it into the front sprocket cover from behind, following the chain.
You should be able to see a couple of threads sticking out in the middle of the nut, or if it has the new nut fitted the nut will be totally flush with the end of the shaft with no threads showing at all.
There has been a discussion that '98 models remain unaffected, although that's not 100% proven or guaranteed yet, but saying that no '98 owners appear to have come forward with the issue either.

Or if you want to look properly you need to take the gear change lever/mechanism off, scratching or marking which position the lever is on the spline, then take the sprocket cover off.
You will highly likely damage the gasket on removal, although a lot of us haven't bothered replacing it without any bother.
Then you can check the nut properly, and clean the sprocket cover out of any built up chain lube.

No point in paying out good money for such a simple job.

If you do a bit more searching on here you'll find pictures and more tips as well.

darrsi · « **Reply #2 on:** 13 July 2015, 07:01:28 am »

There's a few discussions listed on here plus a few pictures.

http://foc-u.co.uk/index.php/topic,16751.msg193040.html#msg193040

Paul · « **Reply #3 on:** 13 July 2015, 07:04:21 am »

As far as I know you can only do it by:

1) Remove gear shift pedal
2) Remove sprocket cover
3) First try and rotate nut by hand
4) Get a decent adjustable open ended spanner and fit it over the flats of the nut that aren't covered by the tab washer, and try and rotate it backwards and forwards.

If it doesn't move it's probably O.K.
If it does move it's probably not.

It's a known fault, I suppose you could call it a 'common fault', except it's not that common.
So you're bike can suffer from it, but it's more likely not to.

Yamaha do actually make a slightly bigger nut, to assuage the worry.
But in reality that's all it's likely to do, because it doesn't address the cause of the problem really.

Oddly enough I reckon you can probably solve the problem (assuming the threads aren't shagged) with the original nut if you want to.

This involves grinding off part of the the lip on the nut, so whilst it tightens on the shaft, it doesn't tighten against the sprocket, it simply fits flush with it. After all, there is no specific reason why it needs to 'tighten' against the sprocket, it only needs to prevent it moving laterally.

If memory serves some Honda sprockets used to be 'loose' in the 1970's.

darrsi · « **Reply #4 on:** 13 July 2015, 07:31:29 am »

Quote from: Paul on 13 July 2015, 07:04:21 am

As far as I know you can only do it by:

1) Remove gear shift pedal
2) Remove sprocket cover
3) First try and rotate nut by hand
4) Get a decent adjustable open ended spanner and fit it over the flats of the nut that aren't covered by the tab washer, and try and rotate it backwards and forwards.

If it doesn't move it's probably O.K.
If it does move it's probably not.

It's a known fault, I suppose you could call it a 'common fault', except it's not that common.
So you're bike can suffer from it, but it's more likely not to.

Yamaha do actually make a slightly bigger nut, to assuage the worry.
But in reality that's all it's likely to do, because it doesn't address the cause of the problem really.

Oddly enough I reckon you can probably solve the problem (assuming the threads aren't shagged) with the original nut if you want to.

This involves grinding off part of the the lip on the nut, so whilst it tightens on the shaft, it doesn't tighten against the sprocket, it simply fits flush with it. After all, there is no specific reason why it needs to 'tighten' against the sprocket, it only needs to prevent it moving laterally.

If memory serves some Honda sprockets used to be 'loose' in the 1970's.

Not that common????

I beg to differ.
If you look at much earlier posts on here there was a bloody long list of people who's nut had failed, or even vanished, some more than once!

Paul · « **Reply #5 on:** 13 July 2015, 08:13:23 am »

To Darrsi

I've met and talked to quite a few Fazer owners over the last fourteen years, probably twenty or more.
But I've only met one Fazer owner that actually experienced the problem.

So from my point of view.... yes it's a known fault, but you're more likely to not have it, than have it.

And whilst there may be a long list of people that have experienced the fault.
There isn't a list of those that haven't
Because there's little point remarking on a fault the bike hasn't actually got.

Sadly I have to go to, work beckons, but the weather doesn't.
In any event, hope you have a good day

BBROWN1664 · « **Reply #6 on:** 13 July 2015, 09:35:37 am »

Quote

98 fazer, 4'600 miles

With that low a mileage, I wouldn't worry too much.

snakeyprince83 · « **Reply #7 on:** 13 July 2015, 12:22:13 pm »

Cheers guys, helpful advice. I will have a look after work.

snakeyprince83 · « **Reply #8 on:** 13 July 2015, 02:37:11 pm »

Also where can I order, or what parts number is the new nut?

Val · « **Reply #9 on:** 13 July 2015, 02:43:01 pm »

Quote from: snakeyprince83 on 13 July 2015, 02:37:11 pm

Also where can I order, or what parts number is the new nut?

The nut comes with a washer:

http://www.ebay.co.uk/itm/141276105948?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

THE KIT CONTAINS:

90179-18006 UPGRADED NUT

90215-21290 WASHER

unfazed · « **Reply #10 on:** 13 July 2015, 03:00:03 pm »

Just to put your mind at rest.

The problem rarely manifests itself before 12000 miles and for some reason the 2002 to 2003 foxeyes seemed to be the worst affected as were many other Yamaha 600s from 2002 to 2006 which used the same type of 9mm nut.
The new nut and washer comes in kit format which includes both and part number is 90891-10124

The problem is cause by the tolerance allowed by Yamaha meant the shaft could be machined too small and the nut could vibrate and the threads fret causing the threads to wear away, losing all thread and then falling off.

Yamaha produced an uprated nut 12mm thick instead of 9mm and recommended a new torque on the thicker bolt of 90Nm.
Do not torque the 9mm nut to 90Nm as you are likely to strip the threads in the nut, there is insufficient thread in the nut to take the 90Nm safely.
This solution works as long as the threads had no damage.

Unfortunately the first time it happened on mine the sprocket fell on to the threads slightly flatting them, exacerbating the problem. After much communication, (I am being nice here) Yamaha finally relented after 72000 mile when the threads of the shaft were almost completely gone to supply the all the parts to repair it (all the gaskets, shaft, bearings, seals and other items) at half price, because they were supposed to have repaired it at 15000 miles when it first happened.

I documented my fix for the problem and uploaded it to the download section. This fix has over 150000 miles on it without problems. I just replaced the Chain and sprockets recently and the fix seems to be effective.

snakeyprince83 · « **Reply #11 on:** 13 July 2015, 05:44:36 pm »

Brilliant, thanks. I have had a look with a torch and I can see some thread, it's not flush but if I'm not going to have a problem because of the bikes low mileage I will get it done at the garage when I take the bike in for its yearly service in a few months time

Panthor · « **Reply #12 on:** 13 July 2015, 07:08:51 pm »

Easy to do yourself, did mine the other week and did this video:
http://youtu.be/QrC0P-VtOmE

unfazed · « **Reply #13 on:** 13 July 2015, 07:18:25 pm »

The video is very good, but he did not torque up the nut properly.

sinto · « **Reply #14 on:** 13 July 2015, 08:04:35 pm »

Here's a couple of recent pics of my nut, ooh err missuss, but it's been on my '98 27500 miles bike I guess from new, but I'm really not in any rush to change it although I've got the new nut and washer to do it, as I think if it was going to come off, it would of by now surely?
I'm waiting till I get a new chain and sprocket set, then I'll do the lot together.
Just thought I'd show it for comparison.

snakeyprince83 · « **Reply #15 on:** 13 July 2015, 08:09:50 pm »

Yeah that is what mine looks like, i can see the thread like that on mine when i shine a torch down on it, i will get it done sooner rather than later just for peace of mind, if it came off and wrecked anything i'd kick myself and my missus would rip my other nuts off over the hefty repair bill haha

snakeyprince83 · « **Reply #16 on:** 13 July 2015, 08:12:21 pm »

Great video Panthor, very helpful, i'm thinking after 4600 miles mine would take a lot more work to get the nut loose than yours? Got the confidence to do it myself now though and will do so soon enough, cheers!

sinto · « **Reply #17 on:** 13 July 2015, 08:12:22 pm »

Everybody makes their own mind up about how they feel about their nuts

I don't have a missus, so it's my shout

darrsi · « **Reply #18 on:** 13 July 2015, 08:50:37 pm »

Personally I prefer the old "prevention is better than cure method".

My 9mm nut fused itself on and my mechanic had trouble getting the thing to budge at all.

sinto · « **Reply #19 on:** 13 July 2015, 08:58:54 pm »

Quote from: darrsi on 13 July 2015, 08:50:37 pm

Personally I prefer the old "prevention is better than cure method".

My 9mm nut fused itself on and my mechanic had trouble getting the thing to budge at all.

I understand darrsi, but I'm saving up for a complete set of sprockets and chain, don't think it'll make any difference now if I wait a month or two to change the lot together, and I'll probably now wait till winter then I can strip the whole back end down including swingarm and then can get an endless chain instead of an open one

Panthor · « **Reply #20 on:** 13 July 2015, 10:25:14 pm »

Quote from: unfazed on 13 July 2015, 07:18:25 pm

The video is very good, but he did not torque up the nut properly.

Can you explain as to how it wasn't torqued properly??
Also just for info my bike was on 16k miles

fazersharp · « **Reply #21 on:** 13 July 2015, 11:28:02 pm »

Im still saying that I have not seen a single 98 owner who has had this issue with an untouched factory fitted nut.
My personal theory is that the 1st bikes came out of one factory and then when the sales took off more outsourced factory's were needed and that is why later models suffer from the wrong spec size shaft being milled from the other factory's.
My 98 17k miles no problems yet although I do have the new nut and monitor the oem one and will change when i do the sprocket and chain

darrsi · « **Reply #22 on:** 13 July 2015, 11:38:09 pm »

Quote from: fazersharp on 13 July 2015, 11:28:02 pm

Im still saying that I have not seen a single 98 owner who has had this issue with an untouched factory fitted nut.
My personal theory is that the 1st bikes came out of one factory and then when the sales took off more outsourced factory's were needed and that is why later models suffer from the wrong spec size shaft being milled from the other factory's.
My 98 17k miles no problems yet although I do have the new nut and monitor the oem one and will change when i do the sprocket and chain

You're all 'special'.

sinto · « **Reply #23 on:** 13 July 2015, 11:51:11 pm »

Quote from: fazersharp on 13 July 2015, 11:28:02 pm

Im still saying that I have not seen a single 98 owner who has had this issue with an untouched factory fitted nut.
My personal theory is that the 1st bikes came out of one factory and then when the sales took off more outsourced factory's were needed and that is why later models suffer from the wrong spec size shaft being milled from the other factory's.
My 98 17k miles no problems yet although I do have the new nut and monitor the oem one and will change when i do the sprocket and chain

Quote from: darrsi on 13 July 2015, 11:38:09 pm

You're all 'special'.

unfazed · « **Reply #24 on:** 14 July 2015, 08:48:15 am »

Quote from: Panthor on 13 July 2015, 10:25:14 pm

Quote from: unfazed on 13 July 2015, 07:18:25 pm
The video is very good, but he did not torque up the nut properly.
Can you explain as to how it wasn't torqued properly??
Also just for info my bike was on 16k miles

The old fear of 90Nm recommended and 80Nm used.

Mine failed originally at 15682miles, a friends failed at 17100miles, but I have come across one on a Thundercat which failed at 12750miles.

I have tighten all I have worked on to 90Nm withou issue

The Fzs1000 is 85 on a 9mm nut, granted the threads are coarser.