CVT rebuild time (again)

So my dash let me know that it was CVT belt inspection time again and so I pulled the covers off and then removed the front (half of the front) sheave to have a look. This setup has been in place for quite a while as this (link) was my last belt and CVT rebuild. I strongly recommend that you go read that too (if you haven't already) as that contains a bunch of other helpful information too.

note the bolts inserted into the rear  (secondary) sheave to "de-tension the spring" which is a needed thing if you haven't done this before and don't have a manual.

Belt looked good but I didn't waste any time gazing at it in situ because my first quick measurement of it showed it was close to tolerance.

So I put it flat on the bench and sure enough, it was close...

and so yep it was getting changed.

The astute may have noticed a crack in the belt between the callipers and so that is something that I'd be keeping an eye on anyway ... Indeed this belt has been on this bike since the above mentioned service and that was at about 100,000km on the bike Odo (actually I'm thinking more like 95,000 but meh).

So with now 162,332 on it I've replaced the belt and rebuilt the CVT with new weights. 100,000km on the belt and same weights, that's not bad (and I'd like to see you get that out of a chain and sprockets).

The Yamaha inspection interval is built into the dash (and you have to reset it when the service is done) at 20,000. This means I've done four prior inspections on this thing including this "inspection" at 130,000(ish)km for replacing a sealon the big end bearing. Everything was within spec so it all went back in. Now the guidance from the 2002 model was to "inspect" the belt but that changed in the 2007 manual to "replace" ... I'll assume this is because of inadequate skills in inspecting staff or just that at $100 it wasn't worth their while even inspecting. 

The weights

But I always disassemble the sheave, inspect everything; replace as needed. 

as you can see, some of the roller weights were starting to show flat spots, this is bad because then they become sliders, and that's another company. The sliding effect is not what was desired by the designers (although an after market one does this) who wanted those weights to roll (or at least I expect that was what they wanted). Once a flat spot has started then it is going to pretty much get stuck in that spot ...

...as it will  get "caught" on that by the pressure of rolling past the lower height. This is bad for a number of reasons (not least will be uneven pressure on the sheave parts). 

This seems like a good time to go back to the last time I did this (here). On that occasion I found that:

 

... except when I weighed them (on a scale that is only reading in grams) I found they were some 18g and some 17g ... when I weighed the bunch they were 143g (or 17.8g on average).
... Interestingly the Yamana ones were on average 19.37g (or 155g for the lot) which as a whole mass acting on the variator is about 12g heavier ... which will mean that it takes a higher RPM for the mass of these to overcome the spring (in the secondary sheave) and mean a higher RPM before the "front" is fully engaged..

This is something to think about so lets look at what the ones which I put in then weigh and what the ones I bought to replace them weigh:

During weighing the (now) old weights I had a few strange situations so I reweighed a second time. Interestingly the sum of all weights was basically identical and the new weights are very close to what the ones I'm replacing now started out as. 

Shouldn't be too surprising when you consider the shavings apparent in the sheave side. Also the new roller weights are now a different material than earlier, and aren't as dark, which I hope means they'll be somehow improved.

I don't know what the material is but I expect that its a polyurethane. I was tempted to rub some graphite into the surface to perhaps help with "sliding" but I read that there is an interaction between graphite and polyurethane as Google AI suggests:

Yes, graphite physically interacts with polyurethane when used as a filler to form a composite material, which modifies the polyurethane's physical properties. There is generally no significant chemical reaction between the two in standard preparations, but strong physical interactions (like adhesion and hydrogen bonding) are formed. 

 so I left it off for this first operation ... I'll inspect and report at the next 20,000 inspection.

So with it all cleaned 

I lubed the interior of the shaft and the nut and assembled it.

torquing the nut on  to the correct amount. The tool I have works nicely by just using the bike's weight and the lever of the arm onto the ground to hold the crank (cos that's what the nut is on) steady while you apply the right (160Nm) torque.

At this point I always start it and check that it operates well before I put the covers back on.

Oh, and I replaced the air filter that's over the rear sheave air intake ... 

Job done