Front Sprocket (with photos)

[Wookee]

Just thought I'd put this thread on as I had to search around a bit for info when looking to change my chain and sprockets on my 03.


This is what a knackered front sprocket with the old 9mm nut looks like:-





You can see that there is a small bit of the output shaft protruding past the end of the nut. Mine wasn't loose (far from it ), but I sought to change it anyway for safety sake. The new nut and washer cost me a total of £2.25 from a Yamaha dealer. The correct part number is 90891-10124 and it comes as a nut and washer kit. The old part number is
90179-18020 and comes as just the 9mm nut which is what another Yamaha dealer tried to sell me (for twice the price of the correct part )




The new 12mm nut on a new sprocket looks like this:





As you can see there is no shaft protruding past the end of the nut and I can tell you there is a lot more thread on the shaft on the inside.


The two nuts side by side to show the difference:





I couldn't find any photos etc online to show the difference hence this post.




You may have watched many Youtube videos telling you all sorts of different things to do it, as a home mechanic I thought I'd share a few tips for those about to tackle this for the first time. It's not a How To Guide, just some tips and info that might help someone else out


I bought my kit from M&P for about £105 and as a heavy duty chain it is a rivet type so you will definitely need a heavy duty chain tool to rivet it together. (I borrowed one from one of the guys at work as we're all bikers.)


The first thing you want to do before cutting the chain is to get the front sprocket nut off. If it isn't loose due to the 9mm problem then you are probably going to need something heavy duty to get it off. The torque settings in Haynes say it should be 70nm, but something clearly happens to them with heat or whatever because it is easily the hardest nut I've ever had to get off, this includes the hub nuts on my 40 year old car . When I couldn't budge it I checked the torque and it was more than 150nm which is as far as my torque wrench goes!


It is quite easy to get it off if you have the right equipment. I wrapped a crowbar in a cloth and laid it across the top of the swingarm through the rear wheel. This keeps the wheel from turning and there is no need to stand on the rear brake. I then made sure the tab washer was as flat against the sprocket as I could get it and used a good quality 32mm socket with a hexagonal face so it fit the nut perfectly. With a normal socket wrench on this I could stand my full 16st on it and the nut won't even move. You need physics to help here and using a 3ft breaker bar does the job quite easily . Note that this nut tightens up quite quickly as I originally had to re-use the old nut while I rode to the dealers to get the new one, a total journey of 6 miles and the nut was back on solidly.


Loosen the rear axle bolt and adjust your rear wheel as far forward as you can which helps when you put the new (shorter) chain on. Then I put my foot on the chain below the swingarm to hold it taut and cut it with an angle grinder.


 I know all the videos a say that when you put the new chain on you need to attach it to the old one to feed it through easily. Not really needed on the Fazer as it's quite an easy path and you can just do it by hand saving a lot of faffing connecting and breaking again.


 When you are connecting the new chain I put the link in above the swing arm then rotated the wheel so that the link is on the rear sprocket as it helps with grip and stops the chain twisting when you're applying pressure to connect it with the chain tool.


 To tighten up the front sprocket nut I just moved the crowbar to below the swingarm and rest it across the chain and torque arm to stop the wheel turning.


 The rest of the process is quite straight forward and the rear sprocket is nothing like as difficult to get off as the front, nuts are torqued to 60nm according to Haynes.






Google links


FZS600 front sprocket nut
2003 FZS600 chain and sprockets
removing front sprocket nut

[Dead Eye]

Nice write-up and covers exactly how I did mine last time round

[pilgo]

    its threads like this one that i hoped to find when i joined you bunch of foccers,cheers mate.

[Ruby Racing]

The first thing you want to do before cutting the chain is to get the front sprocket nut off. If it isn't loose due to the 9mm problem then you are probably going to need something heavy duty to get it off. The torque settings in Haynes say it should be 70nm, but something clearly happens to them with heat or whatever because it is easily the hardest nut I've ever had to get off, this includes the hub nuts on my 40 year old car . When I couldn't budge it I checked the torque and it was more than 150nm which is as far as my torque wrench goes!

Excellent write up and photos.


I had a job getting mine off as well and resorted to the method you described.


Mine is a '98 model with the 9mm nut. As yours was torqued up over 150Nm could this be the actual cause of the original 9mm nut problem? Maybe they were overtightened at the factory knackering the thread on shaft and nut leading to the nut coming loose? When you replace with the 12mm nut maybe it's relying on the good thread that's still there on the end of the shaft? I'm new to this bike, so just throwing this in as a possible cause of the problem.

[fazersharp]

I always thoughtthat you canot properly measure torcque on un-doing
And tourque wrenches say that they may be damaged if you un-do with them

[Wookee]

Excellent write up and photos.


I had a job getting mine off as well and resorted to the method you described.


Mine is a '98 model with the 9mm nut. As yours was torqued up over 150Nm could this be the actual cause of the original 9mm nut problem? Maybe they were overtightened at the factory knackering the thread on shaft and nut leading to the nut coming loose? When you replace with the 12mm nut maybe it's relying on the good thread that's still there on the end of the shaft? I'm new to this bike, so just throwing this in as a possible cause of the problem.

It's not the cause as I torqued mine correctly and then rode it briefly and ended up with it tight again. It's physics, blame Newton not Yamaha :-)

[Wookee]

I always thoughtthat you canot properly measure torcque on un-doing
And tourque wrenches say that they may be damaged if you un-do with them

I didn't undo it, I started at 70 nm to check it then increased by 10's up to 150 with no movement of the but.

[Dead Eye]

The first thing you want to do before cutting the chain is to get the front sprocket nut off. If it isn't loose due to the 9mm problem then you are probably going to need something heavy duty to get it off. The torque settings in Haynes say it should be 70nm, but something clearly happens to them with heat or whatever because it is easily the hardest nut I've ever had to get off, this includes the hub nuts on my 40 year old car . When I couldn't budge it I checked the torque and it was more than 150nm which is as far as my torque wrench goes!

Excellent write up and photos.


I had a job getting mine off as well and resorted to the method you described.


Mine is a '98 model with the 9mm nut. As yours was torqued up over 150Nm could this be the actual cause of the original 9mm nut problem? Maybe they were overtightened at the factory knackering the thread on shaft and nut leading to the nut coming loose? When you replace with the 12mm nut maybe it's relying on the good thread that's still there on the end of the shaft? I'm new to this bike, so just throwing this in as a possible cause of the problem.

I believe the official line from Yamaha was a manufacturing fault where the output shafts were cut too thin causing the binding of the teeth on the splines to be too loose - or something to that effect. It's documented around here somewhere including the correct diameter that the shaft should be and at the limit at which you should contact a dealer and have them replace it

[fazersharp]

And it dosent affect 98s - only after, thats what yam told my local dealer and I have tryed to find others with a 98 (on origional untouched) sprocket and nut and canot find any with the problem 
 
Here http://foc-u.co.uk/index.php/topic,9920.msg101956.html#msg101956