2002 YZ426, threaded shaft, flywheel/stator side...busted


17 replies to this topic
  • regger

Posted March 08, 2011 - 01:00 PM

#1

Sooooo, I was trouble shooting the lighting on my 2002 YZ426 last night....It's street legal, with a Baja Designs dual sport kit, and an external E-Line stator. Blaa blaa blaa...I pulled off the external stator, and the flywheel nut was loose. Gee, I wonder why the lights weren't working, since the flywheel weight was just spinning freely. I'm guessing that maybe I didn't get it on tight enough when I installed it a few years back?? I mean, there's no reason why it should come loose right?
Anyway, I loaded the bike up on my Joe Hauler and took it over to my buddy's house to tighten it up with his impact wrench, and don't you know that the end of the threaded shaft snapped. Not good right? &!@*&%@$%.

I've been searching through posts, looked through the manual and Googled the hell out of this, trying to figure out if the threaded shaft is actually part of the crank or is it connected some other way. From what I can tell, it is part of the crank. I haven't done a bottom end on this bike, so I don't really know for sure. My guess is that I'll have my engine spread across my work bench this weekend right? Do I need to replace the whole crank...and various other?

I'm the original owner, and the bike isn't beat up, so I wasn't really expecting to do a bottom end quite yet. I've only just gone through my first set of tires (and a paddle), 1/2 way through the first set of brakes, and the valves are still in spec from when I bought it in 2002. I've checked the valves 6 times, just last weekend being the most recent? Pretty low miles, just blasting around in the dunes a bit, and Ocotillo Wells. I've always had an extra bike or two to beat on, and figured I'd kind of take care of this one since I snuck it in and got it street legalized back at the end of 2002 if you know what I mean?

In summary, I'm looking at a bottom end huh? Just thought I would toss it out there for a few opinions before I went crazy ripping it apart. Thanks in advance for your comments.

  • grayracer513

Posted March 08, 2011 - 02:10 PM

#2

If you mean the shaft that extends through the OEM stator plate and includes the taper on which the stock flywheel sits, that is indeed the crankshaft.

You can buy just the left axle, but good luck finding one. At TT OEM, the left axle is $295, while the complete new OEM crank is $425.

  • regger

Posted March 08, 2011 - 02:57 PM

#3

Hmmm, that's exactly what I mean. Well, well, well, I guess I'll be crankshaft shopping. Thank you very for the confirmation. Let the games begin as they say. :thumbsup:

  • StoneRacer

Posted March 12, 2011 - 10:19 AM

#4

you need to torque that nut:thumbsup:

  • regger

Posted March 12, 2011 - 02:16 PM

#5

I know, I did actually torque it. The instructions that came with the external stator say 12-15 ft lbs. Which is what I torqued it to when I installed the external stator several years back. Not sure why the flywheel nut came loose. As examine the threaded end piece that broke off it, looks like it may have been weakened from spinning around for quite a few rides - it was kind of dark and weak looking where it snapped. Just a semi-edumacated guess, since this is not the first thing I've jacked up in my life. Oh well, live and learn I guess...at least try to anyway.

Whatever, what's done is done. I'm ripping the motor out as we speak. Got my tusk crankshaft puller and a new crank on order, and I'll be splitting the cases this coming up week. It is what it is. Just need to get this b*tch back together within the next week or two (of course depending on what the top end looks like and any other b.s. I spy while it's apart), so I can squeeze a few more rides in before it gets to flippin hot out in the desert. Then Gorman, Kennedy Meadows and Pismo during the summer. Standard!

  • StoneRacer

Posted March 12, 2011 - 07:07 PM

#6

If you lap the stator to the crank less likely to loosen up, you did use an aftermarket stator right ?

  • brentn

Posted March 13, 2011 - 01:58 AM

#7

Did you say that you tightened the flywheel nut with an impact wrench? As in an impact wrench that has 200ft pounds of torque?

  • 02WR426Cali

Posted March 13, 2011 - 08:32 AM

#8

Sorry to hear about your crank! Wow that is the worst feeling when something breaks like that. But it sounds like the bike has low hours so the good news is your top end should be looking nice still. Just measure all the parts and make sure they are in spec and slap it back together. If your valves clearances are still good and you have never had to adjust them, they are still good.

  • regger

Posted March 13, 2011 - 08:55 AM

#9

I originally used a torque wrench when I installed the external stator a several years back, but this time when I broke it, I used an impact wrench (3/8" with adjustable air pressure, 0-150 ft lbs) and back off the torque to about 10 ft lbs. We tested it on another nut before I used it on the flywheel nut, and checked the torque with his torque wrench. Obviously 12-15 ft lbs isn't that much, so it felt about right actually. When I was tightening it, of course I was sort of feathering the trigger and it pretty much just popped off immediately...I'm pretty sure before I reached 12 ft lbs.

Anyway, I got the motor out yesterday. Nice and smooth, no issues and only took about two hours. As I wait for the flywheel puller I ordered to come, I've been wondering how this thing actually pulls the flywheel off (I mean I know how it works but I guess it didn't really hit me). I've analyzed this in my mind all week and it just ocoured to me this morning...the outside of the flywheel removers needs to thread into the inside threads of flywheel, and it basically pushes out from the middle of the threaded shaft (the end of the crank) and pulls off the flywheel. Makes sense. Well, I just took a look at my flywheel (still attached to the engine of course), and it looks like the threads are gone. Yup, no threads. My guess is that the outside of the flywheel nut ground them off from spinning around, since it was loose. Any suggestions on how to get the flywheel off? Any old school methods? If I heat it up, the heat will transfer to the crankshaft right? Do I need to go to Napa and get a different type of puller with claw type arms that pull it off from the outside of the flywheel (there's a lip on the outside of the flywheel, so it seems like that would work)? Of course the inside part that pushed up against the end of the crank would have to be skinny enough to push into the middle hold of the flywheel as the flywheel come off right? Or is there a flywheel remover than anyone knows of that works to pull off the flywheel from the outside, sort of like how the case splitters work - long bolts that basically press up against the case? Or fire up the flame thrower (just kidding) and nuke the whole flywheel and everything, since the crank and the flywheel are toast? Any suggestions or insight will be greatly appreciated.

In answer to your question StoneRacer, I didn't really ever think about lapping it, only because I never took the stock flywheel off. In other words as it sits, this is how it came from the factory, so the tapers on the shaft and the flywheel should be mated properly right? Since I've never had the flywheel off, there really shouldn't be a reason to consider lapping it right? I reckon the this time around we'll need to check it out since it looks like it will be a new crank and a new flywheel eh?

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  • regger

Posted March 13, 2011 - 10:29 AM

#10

Sorry to hear about your crank! Wow that is the worst feeling when something breaks like that. But it sounds like the bike has low hours so the good news is your top end should be looking nice still. Just measure all the parts and make sure they are in spec and slap it back together. If your valves clearances are still good and you have never had to adjust them, they are still good.

No kidding huh? My big thing was "IT'S NOT EVEN BROKEN" how did I break the crank? You know what I mean? I mean, I've been thinking into the future sort of anticipating dealing with the bottom end at some point, like we all do as our bikes start getting older, but never imagining having to deal with it for such a mickey mouse deal like this. The art and zen of motorcycle maintenance right?

Yes the top end should be fine. I only have one intake valve that is just barely, and I mean just barely outside of the range (loose) that I noticed when I checked the valves three rides ago. I'll suck it back into range since I now have the engine sitting on my work bench and it will be apart soon. Easy enough to deal with obviously.

  • SXP

Posted March 13, 2011 - 02:57 PM

#11

I know, I did actually torque it. The instructions that came with the external stator say [COLOR="Red"]12-15 ft lbs[/COLOR]. Which is what I torqued it to when I installed the external stator several years back.


There's your problem right there. Per the factory manual, that nut needs 35 ft-lb of torque, not 12-15!

And, without being harsh or unsympathetic to your current plight with the crank, what on earth possessed you to try and tighten something to 12-15 ft-lb with an air impact wrench:eek: How could you possibly guess at what the right amount of tightness was? 12-15 ft-lb is not going to snap the tip, nor for that matter would 35 (it had better not) - that wrench was generating waaay more torque then that.

My rule of thumb: air impact wrenches for LOOSENING ONLY. Torque wrenches for tightening only (to specified values).

Edited by SXP, March 13, 2011 - 03:17 PM.


  • grayracer513

Posted March 13, 2011 - 05:23 PM

#12

I can normally tell you with uncanny precision (it's not bragging if you can do it) how tight I make bolts and nuts with the 3/8" Snap-On impact I used professionally for so many years. Often, it just comes down to how far the nut turns after it lushes up. However, tapers introduce another element to it, and you have to be a lot more careful. As the part is tightened over the tapered shaft, it moves inward, and in excess, this can cause several different kinds of damage. For those with less experience, a torque wrench is highly advisable in this case.

And the point about the torque being 35-40 ft/lb is a valid one, too.

  • SXP

Posted March 13, 2011 - 08:28 PM

#13

I can normally tell you with uncanny precision (it's not bragging if you can do it) how tight I make bolts and nuts with the 3/8" Snap-On impact I used professionally for so many years. Often, it just comes down to how far the nut turns after it lushes up. However, tapers introduce another element to it, and you have to be a lot more careful. As the part is tightened over the tapered shaft, it moves inward, and in excess, this can cause several different kinds of damage. For those with less experience, a torque wrench is highly advisable in this case.

And the point about the torque being 35-40 ft/lb is a valid one, too.


Gray - I consider an air impact wrench a potential weapon of mechanical destruction and treat it with due respect. Don't ask me how I arrived at this conclusion:busted:. But, in my defense I was much younger and a shad(ier) tree mechanic back then.

  • regger

Posted March 14, 2011 - 07:29 AM

#14

Indeed the taper introduces another element. Not being a master mechanic by any means, I can certainly admit to not being quite so wise to the ways of the taper, and will never disrespect it again.

I gotta say, was a little skeptical when I installed the external stator, as I was quite aware of the torque specs laid out in the manual. The instructions that came with the external stator specifically state 12-15 ft lbs. I still have them and reread it a few times before attempting to tighten the flywheel nut on this time around. I even called Baja Designs (they made the external stators for E-Line from what I understand) when I was getting ready to torque on the flywheel nut the first time a few years back, just to double check, since it seems like a fairly significant gap in the torque specs. Plus I was sort of friendly with a few of the guys there from going in the purchase my dual sport kit and a few other items at the time. I suppose I figured why should I second guess Baja Designs, right? Here's a scanned copy of the instructions that came with it for your reference:

E-Line External Stator Installation Instructions

The only thing that I can think of at this point is if that wave washer behind the flywheel nut has anything to do with it not needing as much torque. So should I still apply 35-40 ft lbs per the manuals instructions this time around? Still a little confusing. As I fast forward in my mind having that torque wrench in my hand tightening the flywheel nut to the new crank, I'm a little concerned...ya know?

Not that I'm going to dwell on this forever, but I'm still questioning whether or not I snapped it off because I applied too much torque with the impact wrench (even though I understand now that I should have been using a torque wrench solely) because I tested the torque settings on another bolt before I used it on the flywheel nut.

So, my question still remains...are there supposed to be threads on the inside of the flywheel for the flywheel remover to thread into. I still can't quite tell from the pictures I've seen online if there's threads or not? Can't really see how the tool is supposed to pull it off if there isn't threads.

SXP, I couldn't care less about harsh or unsympathetic. I'm a big boy, I can handle it. Isn't that what this life is...bumping around screwing stuff up, fixing it and hopefully growing from it...and talking a little sh*t while we're at it? I'd just like to proceed forward and get this thing running again without too much drama. Any advice or guidance I can scoop up along the way to help matters is greatly appreciated. I'll keep at it until I get it, that's one good thing about me. Even if I have to stare at it for a month, I'll figure it out. Air impact wrenches for LOOSENING ONLY. Torque wrenches for tightening. Check! :thumbsup:

  • StoneRacer

Posted March 14, 2011 - 10:19 AM

#15

Dont know on the 4 stroke on the banshee there are threads and i dont see how it being loose could have damaged them. Do you have a pix of what you add to the stator ?

  • grayracer513

Posted March 14, 2011 - 10:31 AM

#16

Here is where I think the situation went wrong (speculating):

The E-Line instructions appear to assume that the stock flywheel is correctly installed, and remains undisturbed for the purposes of their installation of the external stator. So in effect then, the OEM flywheel is torqued to 35 ft/lb, the nut removed, and the external is then bolted down over an already seated OEM flywheel. That would be entirely different than installing the OEM flywheel, stacking the E-Line on top, and giving the whole set 15 ft/lb of torque.

But even then, 15 ft/lb seems far from adequate.

  • regger

Posted March 14, 2011 - 10:50 AM

#17

I know, I've seen a million of them with threads, but can't find a close up of mine to make sure. It's sort of hard to see on the pictures I took, even if you zoom in, but you can just barely, barely see some faint indications of thread like lines that follow the inside of the flywheel all the way around it. Only really though about half way out towards the outside of the bike.

Here's a few pics of the stator and the flywheel etc etc....

https://picasaweb.google.com/dunesbra

I don't really see how it being loose would damage it either, because it doesn't seem like it would really be moving side to side enough to even touch the flywheel...only outwards towards the cover. Right? It was still tight enough to where I couldn't pull it off with my fingers, but clearly not tight enough for it to be...well, tight enough. The outside of flywheel nut is nice and smooth.

  • regger

Posted March 14, 2011 - 10:53 AM

#18

Here is where I think the situation went wrong (speculating):

The E-Line instructions appear to assume that the stock flywheel is correctly installed, and remains undisturbed for the purposes of their installation of the external stator. So in effect then, the OEM flywheel is torqued to 35 ft/lb, the nut removed, and the external is then bolted down over an already seated OEM flywheel. That would be entirely different than installing the OEM flywheel, stacking the E-Line on top, and giving the whole set 15 ft/lb of torque.

But even then, 15 ft/lb seems far from adequate.

Makes sense. I will be installing it all at the same time this time around, so I will follow the manual's recommendation. And lap it on.





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