So, how does this happen?

[maverick2076]

So, someone want to explain how this happens?

 

[maverick2076]

And yes, the other bolts are missing too

 

[MFP]

So, someone want to explain how this happens?

Bolts must have been somewhat loose to begin with and then they were vibrated all the way out.

 

[Paul466]

So, someone want to explain how this happens?

Friday afternoon assembly line worker enjoining some sake?

 

[barkingllizard]

at the very least, it's an easy fixable issue... not like some other brand's total final drive failures.....

 

[maverick2076]

Are they bolts that come through the pumpkin? Anyone know the size and thread on them, or can look them up for me? I don’t have a service manual on the trip.

 

[Sierra1]

The HOW is easy, my immediate concern would be for how LONG. And, "damn this is tough bike, who needs bolts!" Had a HONDA dealer put anti-seize and not enough torque on the wheel bolts of my RT-P. Got wiggly at about 80mph; felt like the tire just went flat. Bolts were hand tight. And yes, that was the last time we used that dealership.

 

[Dogdaze]

Something to be said for dual-sided swingarm....... Could have ended up with a unicycle.

 

[Boris]

Here is a link to the drive shaft fiche. https://www.yamahapart.com/oemparts/a/yam/53306febf870024560f03e5a/drive-shaft

Looks as if the studs have come out complete with the acorn nuts and the washers. Very odd!

 

[Cycledude]

Wow that seems pretty incredible !!! How many miles on the bike ? Has the final drive ever been removed for any reason ?

So, someone want to explain how this happens?

 

[Longdog Cymru]

Something to be said for dual-sided swingarm....... Could have ended up with a unicycle.

Or a BMW........!

 

[gv550]

Did the studs come loose and fall out? Or did they break off inside the housing?

 

[maverick2076]

21k on the bike. I bought it with 18k. I haven’t had it off yet myself. The previous owner did his own services, which, given this event, is not exactly confidence inspiring.

 

[maverick2076]

So, just heard from the shop. Studs won’t come out of the differential, so it has to be replaced. In addition, the broken bolts wallowed out the holes in the swing arm, so it has to be replaced. Total bill from the Yamaha dealer to repair it: $2970.

I’m not about to pay that. Found a swingarm and differential on EBay for $320. Gonna have a buddy pick it up and we will replace it ourselves next weekend.

 

[OldRider]

So, just heard from the shop. Studs won’t come out of the differential, so it has to be replaced. In addition, the broken bolts wallowed out the holes in the swing arm, so it has to be replaced. Total bill from the Yamaha dealer to repair it: $2970.

I’m not about to pay that. Found a swingarm and differential on EBay for $320. Gonna have a buddy pick it up and we will replace it ourselves next weekend.

Please explain a little better......Did the studs break off in the final drive or just back out? Holes in the swing arm wallowed out just a little shouldn't be a big deal.

 

[EricV]

Sort of sounds like the previous owner left the acorn nuts snug, but not torqued and when they worked loose, the whole assembly moved around until it snapped off the studs. That would explain the wallowed out holes in the swing arm and the pieces of broken off studs in the Diff.
I've seen a similar failure on auto wheels. The area of the wheel, with loose lug nuts, wore the studs down until they snapped off. There was so much damage to the hub that you wouldn't have been able to get the studs out if they were not pound out to the rear, as wheel lug studs are. Ended up replacing the hub rather than trusting the amount of contact left where the studs came thru the hub.

 

[maverick2076]

So, the best they can figure is that the nuts came off at some point, and that movement caused the studs to break off in the final drive. They can’t get the studs out. The movement of the studs in the swingarm has ovaled out the holes in the swingarm enough that the nuts wouldn’t be able to keep it from moving on the final drive, so they would probably need to be tightened up daily or so to keep them tight. They said they could tell the two inside studs broke a long time ago. One outside stud broke at some point in time ago, but more recently than the other 2, and the last one was a fresh break.

 

[Squibb]

The acorn nuts were probably over-torqued IMHO.

Given the way the pumpkin mounts to the SA I would have thought a repair could have been effected here. You would need a good quality stud extractor kit & matching drill to remove the broken studs from the FD.......... .

The SA could be sleeved out if necessary, but I suspect it would be OK without.

 

[EricV]

The acorn nuts were probably over-torqued IMHO.

Given the way the pumpkin mounts to the SA I would have thought a repair could have been effected here. You would need a good quality stud extractor kit & matching drill to remove the broken studs from the FD.
The SA could be sleeved out if necessary, but I suspect it would be OK without.

We will never know, not being able to see the damage first hand.

As a retired machinist, part of doing a job like that is being able to jig the diff so you can drill a strait hole into the remnants of the studs. And how much material was damaged on the diff at the threads for those studs. I've done plenty of extraction jobs, and used an EDM to burn out the broken bits, even carbide. But it can be a very time consuming task.

Sleeving the SA is easy, but again, jig to hold it correctly so you can drill/bore out the holes to prepare for pressing in the sleeves. Ideally you want to bore the holes oversize w/in .001" of the sleeves so the sleeves press in nice and tight. That also means keeping the sleeves to the same size too.

With the right equipment sitting around, it's still a time consuming job and if you can't do it yourself, but are paying someone else's billable hours to do, it's cost prohibitive. Then examine the liability aspect of it. I doubt the dealer had the desire or ability to really do a first rate job and accept liability for it.

Sure, free hand drill the studs and hope you are able to extract the broken bits past the damaged threads w/o snapping the stud extractor tool. Then, if you managed to get that lucky, clean up the holes, if there is enough undamaged threads. Then install new studs with a thread bond/filler like 263 Loctite or perhaps 609.

Even if the thread damage is excessive, it's still possible to TiG weld them and re-drill/tap the holes. Of course, you really should strip the diff down to the bare housing to do this. (and it has to be CLEAN) And again, it's really going to need a proper jig to do this right and hold the diff perfectly solid and square to drill and tap.

And you can get away w/o sleeving the SA, but at the end of the day, doing a DIY repair is very likely going to produce an end result that you may have to keep an eye on and hope doesn't fail. It may never fail. Or, it may break again because the studs were not well supported. Sloppy holes in the SA might contribute to other issues over the miles. It becomes a "pay your quarter, take your chances" type of job.

With a good, well equipped shop, all this is pretty strait forward. The dealership is not that place. And the cost to have a machine shop do this work would be significant. At the end of the day, it's still a repaired set up. Liability again. If it fails, the customer is going to go back to the dealer, not the machine shop.
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Good job on finding some used parts for a reasonable price. I hope the swap goes smoothly. Gives you a chance to see what the SA bearings look like and do a proper grease job before installing the new parts. Read up on that task before you dive in, there are some aspects of the bearings that can catch you if you're not aware of them.

 

[maverick2076]

Ike is all back together and running more smoothly than it has since I’ve owned it. 150
Great miles home this afternoon and we are back in business!