Variator Issues

[monkeybongos]

During a ride, scooter lost its zip.  Less acceleration and top speed, plus a squealing noise.
Took off the cvt cover to find the drive face fins scuffed. 
Drive face came right off, but had a heck of a time removing the drive boss, which has a burr on the far end that
probably made its removal so difficult  (crowbar w multiple applications of PB Blaster)
Had to muscle ramp plate over/past what felt like a ridge near the base of the shaft before it would slide off.
No marks or damage anywhere on the ramp plate.  Maybe the ridge was caused by the burr on the boss?
 
The drive shaft has a groove running the length of it.  Is it supposed to, or did the drive boss burr cause it during removal?

In playing detective, wondering if the variator nut got loose, allowing the drive face to rub against the cvt cover, and some of the metal shavings got between the drive boss and ramp plate, causing a burr on the boss and ridge on the shaft?

2000 miles ago I replaced the rollers, guess it's possible I didn't torque the nut on tight enough and it vibrated loose.
Will be replacing the boss. Main question is should the shaft have such a groove?  And will the ridge-like imperfection near the base of the shaft be a problem?  It'll take some force to get the ramp plate and new boss flush to the end of the shaft.

Hoping some of you more knowledgeable and experienced wrenchers have some thoughts...

Here are pics:

[monkeybongos]

Couple more pics showing the base of the drive shaft and scraping on the inside of the cvt cover by the drive face fins.

Hoping to only need a new boss, but concerned about the markings near the base of the drive shaft.

Btw I did not know to apply any grease to the drive shaft when installing new rollers, but I'll be putting some graphite powder on it from now on.  New rollers went in at 20,000 miles, currently at 22.5K.

[Iahawk]

well that's not a fun thing to find. The groove on your variator shaft (it's actually your crankshaft) is not normal. I wouldn't be too concerned with the fan blades or inside of the cvt cover...and the boss needs to be replaced, as you're planning on doing.

That crankshaft...that should be perfectly smooth with no burs.

I'm sure you'll need to somehow file down or smooth out the bur on your crank to make this all work correctly.

[Iahawk]

looking more closely at the crank...it that a mushroomed out part at the base of the crank? Is that what was keeping your boss on tight?

Looks like your splines are a little boogered up, too, but as long as the outer drive face slides on it shouldn't be a problem.

[Ruffus]

@MB, like Iahawk wrote already, your crankshaft has to be as smooth as possible and without any groove.
Groove was caused by pulling the boss off forcefully.
This sleeve/boss has to rotate/ move on the crankshaft freely with minimal axial play.
(1/10th of a mm or less)

To achieve this smoothening:
- take off as much as neccessary upheaved material on this shaft by a very fine file
(key file/diamond grid like a nail file)
- measure with a caliper all the time
- when most of this groove is planed
- start the motor, let it idle and smooth the crankshaft with 200-1000 grid sanding paper
- just hold it there
- replace your CVT boss
- cure the crankshafts teeth ...
- put a new fan and nut or best a whole new CVT in there...
It's a repair and MIGHT last. Torque for this CVT nut is 90nm. A minimal smear of copper or ceramic grease helps with assambling.
And wear good gloves during grinding.

[monkeybongos]

Thanks for chiming in guys. Appreciate it, even if it's not all good news.

Iahawk, the damage you see at the base of the crank made it difficult to get the ramp plate off, but pretty sure it was the burr on the boss that made it so tough to remove.  Shavings from the scraped fins are a prime suspect for that crank damage, but I'm puzzled by how any shavings got in there, as the ramp plate and boss seemed to be flush against the end of the crank.  Maybe if the nut loosened up enough to allow the fins to scrape the cvt cover, the boss could have slid up enough to make room for shavings to get in and scar the base of the crank?

Ruffus, your mechanical knowledge is extensive and invaluable, so I kinda cringed when you said any repair done MIGHT last.
Don't want to even think about having to replace the crank.
Two questions:
1)  how do you "cure" the crankshaft teeth?
2) any reason the fan in the photo wouldn't function properly? (if it easily slides on to the crank)
Not opposed to a new variator kit, but aside from the scraped fins every other part looks unscathed.

[Stig / Major Tom]

Yes, you might get away with removing any burr in that groove on the shaft, and smoothing it all.
Maybe the bit of grease will just ride in there without migrating .....?

I'd replace the boss and the nut.
I use a new nut every time - both front and rear, when working in the CVT. They are not expensive and you'll have a better chance of properly torquing a new nut with fresh threads.

Yeah - you've lost a very little bit of cooling with the damaged fins - but it surely won't be a big deal...and could be reused if it slides on easily and if there is no 'play' in it over the end grooves of the shaft.

good luck!

Stig

[Iahawk]

I'm just throwing this out there....but absolute worst case...as Ruffus said, if it doesn't work? It is not difficult to crack this motor and take it apart. I'm in that process now. $50 USD worth of gaskets and o rings plus a flywheel removal tool ($12?) and a starter clutch nut socket ($20+) and then another $150 (?) for a crank and $6 in 2 crank oil seals.

I'd sure give it a try to first file off the burr and smooth things out...these are tough little motors that are routinely abused around the world and live to fight another day. 

[CROSSBOLT]

This sleeve/boss has to rotate/ move on the crankshaft freely with minimal axial play.
(1/10th of a mm or less)

Hate to ask this but isn't the rotation of the sleeve/boss the real CAUSE of this damage? The ramp face is the thing to slide on the sleeve, ain't it?

[Ruffus]

@MB,
 YOUR Two questions:
1)  how do you "cure" the crankshaft teeth?
2) any reason the fan in the photo wouldn't function properly? (if it easily slides on to the crank)

ad1) take this mushroom slighty off with a file or DREMEL tool (cover the oil seal) to fit this M12 x1.25 nut without roughness until the crankshafts thread.. not too much, just make the nut fit.

ad2) yes, this fan could fit again, but check its tight seat on the crankshaft, otherwise same game again... keep us posted.

Looks to me as this knob (in your sixt pic) was formed during mounting your new rollers 2000 mls ago. Then pulling off the boss grooved in, or that kind of thing...not easy to say from distance.
 The groove, properly smooth would not cause a prob. It's more the danger of starting wobbling.
Like sayed, I would bite the bullet, and buy a new CVT.

[monkeybongos]

Replacing the nut is a good idea, Stig, one I wouldn’t have thought of.  Hoping Ace or Lowes will have em.

Good reminder hawk about these being tough motors as yes, they are regularly abused. 

Karl, not sure I understand your question. If you’re thinking the burr on the boss damaged the crank, maybe, but then what caused the burr to form?  As for the ramp face, believe that slides on before the boss. It definitely doesn’t fit over it. 

Rufus, I’m a bit confused about filing off the mushroom so the nut fits smoothly.  It already threads on smoothly, as the marred areas are all below the threads where the nut doesn’t go.
As for the knob in pic #6, how would it get formed from mounting the new rollers?  I ask as I don’t want it to happen again. 

Could sure use a dentist or oral surgeon for a neighbor right now

[Ruffus]

Rufus, I’m a bit confused about filing off the mushroom so the nut fits smoothly.  It already threads on smoothly, as the marred areas are all below the threads where the nut doesn’t go.
As for the knob in pic #6, how would it get formed from mounting the new rollers?  I ask as I don’t want it to happen again.

Could sure use a dentist or oral surgeon for a neighbor right now.

@MB,
A) if the nut (preferable new one M12x1.25) already fits on smoothly, OK, no further action required.

B) for this "knob" within your boss: IMO was caused by mounting the CVT assambly 2500 mls ago. Either material fault or too hard locking the nut....or, or...

EDIT: my theory on how this knob happened (after I watched your very first picture [fan and nut] again closely) is: when you mounted last time your new rollers, a piece of this nuts inner thread (see demaged thread inside nut) broke off and was pushed with the boss along the driveshaft causing groove and knob.
As I said, only my theory.

-anyway, the boss should move smoothely on your crankshaft (degrooved),
-both CVT alu parts (fan and other) should move without any significant feelable resistance, both lateral and axially on your boss..
(copper or ceramic paste on the crankshaft)
-mount your rollers with your right hand behind this ramp which holds them in place to avoid collapsing and causing trouble again

-drivebelt in between
-new fan on it
-put this big toothed (kickstart part) shim on
-thread a new nut, torque wit 90NM, deal done..

Pics from a 200i (176 ccm) motor for llustration, what I meant.

[monkeybongos]

Thanks for the Master Class in variator repair, Ruffus!

[monkeybongos]

Sanded the shaft w 1200 grit while idling the motor.
Groove on shaft still there, but edges smooth, and mushroomed area at the shaft base also smoothed over.
Carefully slid the new boss on and it fit flush!  (see pic)

However, the drive face wouldn't go on over the buggered splines.  So ordered a new drive face, not
knowing if it was the splines or drive face teeth that was the problem.
The new drive face wouldn't go on either.  Got a diamond file kit for Harbor Freight, applied about
3 strokes to each side of the splines, and it fit, feeling pretty secure!  Put everything together (used dry graphite lube on the boss)
and torqued a new nut to 64 ft lbs.

Rode 200 miles past couple days and it seems as good as ever.  Might have a little more judder at low speeds (could be my imagination) and acceleration at high mph as good or better than before.
Got to 70 wot (closer to 65 actual) and it seemed to be still gaining speed but had to slow for a red light.

Initially when I put the new rollers in, they didn't appear to have a heavy side, so I just put em in randomly.
Upon closer inspection the second time around, it looked like one end had slightly thicker metal--subtle difference b/t the heavy and lighter side, had to look hard to see it--so I placed all 6 rollers w what appeared to be the heavier side facing left.  Does it make sense that this would have the effect of using slightly heavier rollers (vs when randomly placed, where a couple would likely be reversed), leading to a bit slower takeoff w stronger high speeds?

Anyway, thanks all for the suggestions, hoping this repair holds for the next 20K miles.

[Ruffus]

@mb, this is good to read, congrats to your success!!
This sleeve looks very good to me. The groove inside should not give any trouble as long the nut is properly tight.
Check once in while, methinks this nut loosening was the culprit.

I would not see a plus or minus to interwave the rollers alternatively.
Only heavier (+1-2 grams) rollers might give a more decent acceleration and at high speed lower revvs, ergo less consumption.