thicker sprocket nut worth a check

[bandit]

I would just keep a eye on it & change with sprocket when required.

[vinnyb]

cool, ta

[fazersharp]

cool, ta

Some say that the age of the bike does not matter, others say that the output shaft was done to the wrong spec - too small but then that fault only started after 98 (my theory ) but some time later torwards the last ones the shaft issue was noted and changed with the correct size and every one else has to make do with the wider nut, which will not harm to use when the set is changed and in the meantime keep a close eye on it.
If it is nice and clean in there then you can see it if you lay down with a tourch, if you cant be arse to take the cover off, maybe best to take the cover off to see properly.
     

[vinnyb]

Thanks again Fazersharp. Given all that information, I think for the sake of a few quid versus the damage it causes, should shit happen, I'll just buy the thicker nut and washer and get my friendly neighbourhood bike mechanic to swap them over. He'll have an air wrench and a socket big enough to fit. Does the new nut guarantee against future failure?

[mogster]

they are not  tight :eek

[fazersharp]

they are not  tight :eek

They started off tight at the factory but due to an undersize shaft they can work loose, have a search on here and you will find loads of stuff about it.

[Panthor]

Mines a 2003 and the nut started to loosen so I changed it for the upgraded one.
By the way Yamaha dealer is cheaper than eBay for it.

[vinnyb]

Doh... Just bought one from Ebay. Just out of interest and to piss me off. How much cheaper? But do I really want to know? Yeah go on then, how much cheaper?

[Panthor]

Bought mine last year and it was £2.92 for the kit which was nut and washer.

[vinnyb]

Bugger :'(

[daviee]

lol dont worry i paid ebay price aswell still cheaper than a wrecked engine

[Adam2201]

I put the thicker sprocket nut on mine not long after I bought it in 2015, having read through all the woes on here. The old 9mm nut was still on foccing tight when I took it off, no sign of any issues.


Came to change my chain and sprockets yesterday and when I bent back the lockwasher the nut was loose!  I don't think it would drop off mine due to being the older model with the thicker sprocket cover, but it's annoying to find it like that after replacing the nut.  Can't see any damage to threads, so I'm really not sure what's happened - I read through a few posts on here when I fitted it and torqued down to 80nm dry, so will try 90 with threadlocker this time and keep a better eye on it this time.


Bonus picture of old vs new sprocket just to shame myself - as you can see the old one is an advanced model with special bent teeth for chain retention  [size=78%].  Surprisingly, chain was still within spec when I measured it properly, and didn't seem to pull off the back sprockets excessively.[/size]
[/size]
[smg id=2953 type=preview align=center caption="20170317 233943"]

[fazersharp]

Kind of also backs up my theory and the reason that every time a 98 says they had the issue I always have to ask. Had it been replaced previously or is is an original factory fit one.

I think the proper way to get the correct tourque is that all settings are done with engine oil and not dry. But if you do that then you cant use locking compound, so I gues locking compound talso takes the place of engin oil to get the correct tourque 
How many miles did it take to get your teeth like that

[Adam2201]

I honestly don't know if it's original - I can't find the advert from when I bought the bike now, but would assume it had been changed before I bought it.  Did the original ones have any distinguishing features? It's at 30k miles now and I should have changed it 6 months ago when I did the clutch cable as I could see it was going downhill.


My experience is from pushbikes, and before reading the threads on here I would have said that loctite was classed as a lubricant when you're doing something up (just like oil or grease), but I'm no expert.  Will be going belt and braces on it tonight when I put it back together (taking the opportunity to regrease swingarm and shock bearings/bushings), so hopefully I won't see any issues with it after.

Reading some of the earlier comments now, I don't think I'd got the lockwasher spread right accross the nut flats last time, so it may well have vibrated loose from that - it makes sense that I did something wrong as it didn't have any issues before..


Edit: not sure why the font size keeps going down to 1pt!

[Kenbob]

The mechanic that does the work on my bikes said to me about the sprocket nut issue on my 600, Yamaha may have brought out a bigger sprocket nut but not everybody knows how to fit sprockets nuts properly.
I have a 2002 600 and it has the thinner  nut still on it, I have faith in my mechanics ability to fit the nut correctly after He fitted a new chain and sprockets and I'm quite sure he wouldn't allow me to ride the bike knowing the he was the last person to refit it.
I guess it's yamahas way of saying hey guys we've addressed the issue with a bigger nut but if you can't fit it then that's your problem.

[Fazerider]

I can well believe that is the original sprocket. It certainly looks like it has 30,000 miles of wear and has the plastic cushioning to reduce noise… these are normally quite pricey (until Ognibene started offering them recently) so it’s not likely to have been changed.
My 12mm nut did the same thing a few months ago, it was still prevented from rotating by the lock washer, but appeared to have jumped one thread so the sprocket was able to slide slightly on the splines.
I don’t think you should beat yourself up about it. I torqued mine up correctly with threadlock too, the problem is nothing to do with undersized shafts (at least, not until they’ve been battered to death by a completely loose sprocket). Yamaha focced up by designing it with a completely unsuitable thread pitch, it’s far too fine for the sort of loads it experiences.
To get round this they applied a threadlock compound that was at the superglue end of the spectrum, hence the need for a 6ft breaker bar and the rifleshot sound effect when the original nut is undone. I suspect Yamaha had enough complaints about this from dealers that they switched to a weaker compound for later production.
Despite the extra turns of the deeper nut, the strength is marginal so it will eventually come loose. For most people the C&S will need changing before that point occurs provided you use a strong threadlock compound on a scrupulously cleaned thread.
I’d be interested to see a pic of the inner side of your sprocket, I noticed mine has heavy wear on that side so it is possible that a slight misalignment of the front and rear sprockets causes a sideways hammering effect on the front which might explain the nut getting bumped outwards.

[Adam2201]

It might be original then - 30k seems like a lot though!  Will get a pic of the other side when I get back home.  The chain has 5DVN Japan printed on it and definitely has a rivet link though, I think the originals were endless?I remember it being fairly difficult to undo the 9mm nut - I had to put a pipe on my breaker bar and lean on it, and when it let go I got the shotgun effect you mentioned (not as bad as the nut on the clutch adjuster though!).
 
I think the bike had a Scottoiler at some stage, as when I got it the vacuum cap on #1 carb was missing, so it might explain the longevity if it is original.  I use spray lube once a week or so, but I've not been fastidious about cleaning it so it's done well really. 

[mtread]

Could explain it. A Scottoiler would easily mean 30K +