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[stargazerinwg]

My 2017 FX (purchased new in 2019) has about 14,000 miles.  I had the chain kit on it for about a year and then put the belt back on when the chain was worn out.  I heard some unusual noise, kind of clicking like, particularly when regen would kick in for a week or 2.  I checked belt tension and watched the wheel and belt with the bike on the track stand and the motor running.  Unfortunatley, I didn't see anything.  It failed on the way home the other day and I found that all the splines in the pulley were nearly gone.  You might be able to see it in the photo.  The shaft on the motor has a little damage but I think a new pulley will still work.  I was at the dealer today to order it for $101+ and was told it may take 2 or 3 weeks.

Just wondered if anyone else has had this problem.

[TheRan]

That's a very surprising failure mode, I've not even heard of the torquier R models doing that. Generally it's the belt that is the weak link. Interesting that you have the 20t and not the 18t pulley (which means even less load on it), I assumed the 6.5 would use the smaller pulley like the 7.2 models do. You could change your order and get a little bump in torque, presumably you have the dongle to adjust the speedo to the different ratio and you had the chain kit or you have the dealer do it.

[T.S. Zarathustra]

If I remember correctly the instructions say to use Loctite 620 on the splines when assembling. Maybe check before you put the new one on.

[stargazerinwg]

The dealer did tell me when he looked it up, that it called for the 18T.  The parts manual I have (think I downloaded it from here or from Zero) calles for 20T and the part number is stamped into the part.  I prefer the 20T and that is what I ordered.

I didn't know there was a dongle for adjusting the speedo. Back when I installed the chain kit, Zero told me to take it to the dealer to get the speedo correct; they wouldn't give me the password to change it in the interface when I connect a laptop to it.  I think someone did eventually post the password on this forum but I haven't gone back to try using it.

When I put it back on after the chain kit, I used the newer Torx screw (rather than the original allen head) and used blue loctite.  It was snug when I removed it and there was no evidence of it being loose, e.g., paint scraped off.

When I get the replacement installed I think I will check the screw every few thousand miles just in case.

[TheRan]

Even if the bolt were loose it shouldn't cause that sort of damage, it doesn't change the forces involved. What I do notice in your photo is it looks like there's still a fair amount of the splines left, which would suggest that the ones on the motor shaft weren't tall enough to take up the full space within the pulley. If they were worn down for some reason, perhaps if the chain sprocket was undersized and forced on or too loose and narrow and allowed to move side to side, then that would increase the load that each spline had to carry and could result in them shearing off. Or that amount of tolerance between the splines could be completely normal. If you could measure the diameter of the splines and someone else could who has a bare motor handy I'd be curious to see how it compares.

[T.S. Zarathustra]

The dealer did tell me when he looked it up, that it called for the 18T.  The parts manual I have (think I downloaded it from here or from Zero) calles for 20T and the part number is stamped into the part.  I prefer the 20T and that is what I ordered.

I didn't know there was a dongle for adjusting the speedo. Back when I installed the chain kit, Zero told me to take it to the dealer to get the speedo correct; they wouldn't give me the password to change it in the interface when I connect a laptop to it.  I think someone did eventually post the password on this forum but I haven't gone back to try using it.

When I put it back on after the chain kit, I used the newer Torx screw (rather than the original allen head) and used blue loctite.  It was snug when I removed it and there was no evidence of it being loose, e.g., paint scraped off.

When I get the replacement installed I think I will check the screw every few thousand miles just in case.

You put blue Loctite on the screw. But what about the splines? I believe the 620 Loctite for the splines, that I saw mentioned in some Zero instructions, is called "green".

[ESokoloff]

………Interesting that you have the 20t and not the 18t pulley (which means even less load on it), ……….

Actually the larger 20T will put greater torque on both its input & output surfaces (compared to a 18T)

I’m not seeing how the sheave clamps down on the splined hub.
On non splined shaft applications the hub has a thin slit that allows the diameter of the hub to decrease while being drawn into the tapered sheave via jack screws & this creates clamping force.

[stargazerinwg]

I'll try to measure the shaft splines and what's left of the pulley splines when I get the new pulley.  I still don't understand how this happened.  Maybe there was just a problem with the pulley.  I'll compare it to the new one and see if there is anything different.

My plan is to use a new torx 10mm screw (new from Zero) with the new pulley and torque it to 60 NM.  I don't have a torque spec from Zero for it.  60 NM is the torque spec for my KTM 350 10mm countershaft sprocket screw, unless anybody knows what the spec actually is.

I didn't use any loctite or anything otherwise on the shaft and splines when I put the pulley on.  What do others think?  When I removed it for the chain kit, it just slipped off and there didn't appear to be anything on the shaft or splines.

[TheRan]

If the pulley is wide enough that tightening the bolt clamps down on it (so it's not narrower than the splines on the motor shaft) then retaining compound on the splines is unnecessary, you're just making it harder on yourself the next time you have to remove the pulley.

The torque spec for the bolt is 72Nm, section 30-3: https://learnerresources.s3.eu-west-1.amazonaws.com/113502/learner_resource_uploads/40f7e0964aeb72b7aa6a9627c0/XMX%20Service%20Manual-AD.pdf?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAQZVLRHER6MLZQEAI%2F20241120%2Feu-west-1%2Fs3%2Faws4_request&X-Amz-Date=20241120T205030Z&X-Amz-Expires=5400&X-Amz-SignedHeaders=host&X-Amz-Signature=bd384cadfee05846df63f4c7c036975726eaa349a8c6fc50dde1dc5f1f274d44

[T.S. Zarathustra]

Sorry. My mistake. You're supposed to put Loctite 680 on the splines, not 620.

[stargazerinwg]

Wow.  I sure appreciate all this informnation.  Thank you very much.  I just got the Zero Service Manual.  I wasn't aware there was one and had been using the unofficial manual.

I got the new pulley and spacer and unfortunately I didn't read your helpful posts before I worked on it today. 

The new pulley slipped on nicely and doesn't appear to have any slop or play in it.  The spacer matches the back surface of the pulley but its I.D. is larger than the motor shaft O.D..  I used some red and tacky grease to get it aligned on the pulley for installation.  Otherwise, it could be tightened off-center.  This seems a little jankity to me but that is the way it is.  I didn't use anything on the splines - when I took the pulley off before installing the chain kit, it was clean, i.e., no evidence of any Loctite 680 on it.  It came off with no pressure or tools needed.  I wonder if the use of Loctite 680 is a new thing.  I used blue loctite on the T50 M10X25-10.9 countersunk head screw.  I was able to torque it to 50 NM.  When I trid to torque it to 60, it was too difficult to hold the pulley and I was concerned I might damage the torx fitting.  It is really awkward doing it through the swing arm pivot holes in the frame and difficult to hold the pulley.  I don't have an old drive belt to make the tool the manual shows for holding the pulley.  I think the drive belts are pretty expensive.

I'm going to take it for a short test drive tomorrow to check it out.  I'll get some Loctite 680 and work on a way of holding the pulley better and go back through the process of installing the pulley again.

[TheRan]

The fact the spacer is loose on the shaft really makes me think the splines are worn down, but perhaps someone else who has had theirs apart can share their experience. The only reasons I can think of that Zero would recommend putting retaining compound on the splines are to make the job hard enough that fewer people want to do it themselves, and to stop the pulley sliding off if the bolt should loosen. For the latter that's very unlikely if the bolt is properly torqued and has thread locker itself, and if you manage to miss the bolt coming loose personally I would rather have the pulley move and maybe that would be more noticeable.

[T.S. Zarathustra]

The reason for the Loctite is to prevent slop. Slop as in the sprocket moving slightly back and forth each time there is drive or brake forces from the motor. Since electric motors have high "engine braking" it is important that there is no slop. If there is slop it is like hitting the splines with a hammer each time you switch from one to the other. That deforms the soft aluminium, ending with the splines stripping.

[TheRan]

But the pulley isn't just loose on the shaft, it has the bolt clamping it in place. I don't believe an FX has enough regen to overcome that. And even if that was the case then I'm sure there are better gap filling compounds out there that don't also provide as much "stick" and require taking a blowtorch to the pulley to get it to loosen up.