Countershaft sprocket nut

Hello all;

After a few changes of the countershaft sprocket my nut has about had it. I see that the F model uses a tabbed lock washer behind a standard nut 90179-18001-00 . I wonder why the R uses the "dented collar" style locknut 90179-18010-00?

Has anyone found a non-Yamaha nut that will work?

I believe they're using the nut they're using on the WR-250R because, once the nut is staked in place, it's a more secure way of locking it in place.

A WR-250F does use a locking tab that gets bent over the flat of the nut, but you need to have the shaft splines sticking out past the sprocket a couple milimeters for the locking tab to engage with.
I don't remember the WR-250R having that design feature, especially since the back side of the WR-250R nut is flat, while the back side of the WR-250F nut is specially relieved to clear those couple milimeters of spline sticking out past the sprocket.
Also, you need a new locking tab each time because they're not meant to be reused.

You're also supposed to use a new nut each time you remove it on the WR-250R, by the way.

To sum it up, don't reinvent the Yamaha wheel and just go buy a new nut made for the WR-250R. :)

So if I change spockets twice on every ride to my ORV park, how many nuts do I need for one year of riding? 40?

You might.

The thing is, the part of the nut that gets staked down into the shaft cutout gets tweaked from staking it down and then bending that part back up when you need to remove the nut.
Odds are, that same part is going to line up with the cutouts in the shaft if you want to reuse the same nut, and that part won't be as strong as it was when new.
This is why the Service Manual says to use a new one - so it won't loosen and come off when riding the bike.

I guess it's ultimately up to you.

At least they're cheap. :)

Well, I guess if it's up to me then, I'm going to engineer a differant way to lock it, so it is quick to remove and replace. I'll keep you posted.

I'm going to drill the nut for tie-wire.

Wrote this on another thread too, but what's the best way to stake down that nut once you have it back on? Is there a specialized tool?
Thanks!

Also, are other people taking off their chain when they swap out the front sprocket? What a pain in the ass that was with the chain on. Just not much room in there

The tie wire worked fine.

granite4brains wrote:

Wrote this on another thread too, but what's the best way to stake down that nut once you have it back on? Is there a specialized tool?
Thanks!

Also, are other people taking off their chain when they swap out the front sprocket? What a pain in the ass that was with the chain on. Just not much room in there

Did you loosen the rear axle and slide the entire rear wheel assembly as far forward as possible?

I ended up finding something that was the perfect size of the indentation on the shaft. Just used that with a hammer and it staked the nut perfectly. Still seems sort of quirky though especially compared to my buddy's bike which had what I think he called a snap ring?

Captain Midnight wrote:

The tie wire worked fine.

Any chance of a pic of how you did it please? Did you drill through both nut and sprocket?

Can't quite see how it works - sorry

Brian

I don't stake the nut at all. I put a little locktite(blue) and make sure to torque it right. 8000kms and not a hiccup.

I bet your front sprocket is worn a bit its really hard to see the wear unless you have a new one to compare it to. They only cost about 15 bucks dont put a new chain on the worn sprocket, it wears the chain fast.

Not sure how much torque, I just tighten stuff like that to 30-40 ft/lbs.

I'd just stake the nut down, you can do this a bunch of times before the nut wears out. The nut is the same as the nut on the end of car axles, no one ever buys new nuts for those, or even thinks about em lol.

torque spec for the front is 90 Ft LBS.
Would link you the service manual but Moderators asked not to because of copy issues.

Waking up an old thread..

How're you guys removing the lock ring? Do I need to get in there with a fine tip and try to bend the metal outwards? Or hammer a screwdriver in the middle?

Thanks

I drive a small flat blade screw driver that's about the same size as the slot in the shaft straight into it or like you say hammer a screw driver in the middle.

I've been through a 4-5 sprockets now and will be getting a new counter shaft nut next time as the lock ring is getting weak.

Thanks Biglake, that worked just right, new sprocket on and torqued

For all of you that cannot get the little aluminum nut tabs bent up that are staked down against the indentations in the output shaft. I could not find a tool small enough and gave up and removed the nut WITHOUT bending up the stakes. This was on a new bike with 1000 miles and original nut. It was a little hard getting off, but the soft aluminum nut did not harm the steel output shaft threads in any way. So it can be done if needed. What tool do you guys use to get under the staked nut? How many times do you reuse the countershaft nut? Also it's hard to measure the torque on a wrench when your balancing the bike, holding down the rear brake pedal and trying to apply 70 ft lbs. with the opposite hand. I hope I got it tight enough but will check again. I got PAST the previous indentations so maybe the new OEM sprocket is slightly thinner or I got it tight enough.

I used a small screwdriver to open up the tabs.

The tabs are too soft to sustain multiple extractions and insertions; I used a new nut when I changed my sprocket. Some people reuse the nut without re-engaging the tabs, relying on blue thread locker instead; I am a bit paranoid, so I used both thread locker and a new nut.

You may want to consider this tool next time: it makes sprocket change much easier.

Aluminum nut?

Correction - the nut is definitely ferrous material (not alum). I checked it with a magnet. But if is softer material compared to the output shaft. Not as soft as aluminum though.
Aluminum threads are too weak I am sure to hold up to 70 ft /lbs. or torque and maintain tightness. It's very lightweight and doesnt rust so I am not sure what material it is?
I've seen a few posts about worn splines and damaged output shafts though...so I will be closely monitoring this.

Yes, torque that new nut down correctly and stake it to the shaft correctly, and I doubt you'll have a problem.

The only way I believe the shaft splines can get damaged is by a nut not properly torqued down and/or not providing sufficient tension on the sprocket (too loose or missing the washer or the wrong washer or wrong nut or the wrong front sprocket) and allowing the sprocket to rock back and forth on the splines.

Personally, I don't see the point in messing with this setup and installing the front sprocket any other way than the way it came off.