Help with Swingarm

[Beemeridian]

22

[CycleRob]

Help is here. I just got off the phone with Dave. He has 2 options:
1--Take it to a dealer with a potentially huge repair bill
2--Fix it himself.

While on the phone we got synchronized with both our computer screens, hundreds of miles apart, looking at the same exploded diagram on page 33.19 of the BMW CDR manual. I literally had to twist his arm to take option #2. The blow-up diagram shows it's not complex . . . . just a few big simple parts like the splines, pivot points and the driveshaft that need to be carefully, patiently aligned as they are assembled with minimal force.

The best way to repair any thread damage is with a tap. Lacking that unobtanium large bolt diameter fine threaded tap, removing the swingarm and threading the pivot bolt in from the inside will clean out both damaged thread portions with hopefully something less than minor damage. To be clear, . . . . Dave . . . , the internal female threads and the pivot bolt threads must be oiled up, then threaded in from the inside where the swingarm goes, the 10mm internal hex threaded end going in first by hand. Inserting the 10mm Allen from the outside and loosen the threaded pivot pin until it comes all the way out, "cleaning" both pairs of the slightly damaged threads as it's removed. When/if it starts going hard, a back-n-forth rotation may be necessary to expel the tiny thread fragments so they can be vacuumed or blown out. After a few harder effort turns, reversals and blow-outs, it should start going increasingly easier until it comes out.

Then, it's just clean it up, put it all back together . . . . . and Ride!

FYI, this repair may take "about 3 weeks" because of Dave's heavy employment load. If he was a lot closer than 8 or 9 hrs away, I'd be there after the rain stops.

[Beemeridian]

22

[CycleRob]

It just occurred to me about a possible error in your heating process that might explain why this routine adjustment had serious difficulties. The heat needs to be evenly applied to the massive Aluminum area around the pivot bolt, but NOT on the bolt itself.

If just the bolt was heated, it would expand, bind in the female threads and come out hard. It could even damage the threads in what must be a steel insert pressed into the Aluminum swingarm.

Even if my guess about an error in heating is wrong, anyone making this adjustment after this now knows what to do and what NOT to do, besides the general instructions in the digital service manual.

[ruddy]

If another bolt with the same thread is available, you could use it as a "thread chaser." Use a small triangular file to cut two or three slots perpendicular to the thread. Then do as Rob said. The bolt will act kind of like a tap and will clean up the threads. The slots will act like the flutes in a tap and give the shavings a place to go. Use lots of light oil (cutting oil would be good) and reverse the bolt occasionally when you're "cutting" the damaged threads. This is an old gunsmithing trick.

[Boxer]

anyone making this adjustment after this now knows what to do and what NOT to do

Color me dumb. I still don't know what or what not to do Rob. Should he have removed the screw with the bike on the side stand? Or maybe supported the bottom of the transmission case? I guess I don't understand how the swingarm pushed up on the bolt.

[towerworker]

Dave,
I will be happy to help whenever you're ready. I'm not real smart but I learn fast.

Wayne

[towerworker]

Dave,

I have a Craftsman tap & die set that goes up to 1/2" and possibly have access to similar metric sets at our shop with various sizes. I looked at the referenced BMW manual I have on my computer but didn't see the size of the bolt that is in question. Do you or anyone else know the size?

Wayne

[Airman]

Is this something that needs to be done? You guys are certainly encouraging me to stay up front tinkering on the valves where I know what I'm doing. Sounds like an unpleasant task.

[Beemeridian]

22

[markg]

You should try to get whats called a "bottoming tap" to clean up the internal threads. This is a tap without the taper on the end, and is made to finish off the threads in a closed hole. One uses this after the normal tap is used, and will clean up the threads all the way down.

best of luck

[Boxer]

David, Those notes are unclear but I think they are referring to the taper bearings of the swingarm, with the inner and outer races. I don't see in my Haynes manual a reference to "needle" bearings anywhere relative to this area you're working on. I think they're just telling you to make sure you line up the pivots with those inner races as you replace them in the swingarm.

I have scanned the pages in my manual concerning this project and will place them at the following location for you to download quickly: http://www.bmwmoga.info/booty

However you will need an ID and password to access that directory. I will PM those to you now. Look for them and let me know when you have downloaded so I can remove them.

If all else fails, take a deep breath, relax, go back inside and have another beer, then put it off until you have more info.
Good luck pal.

[CycleRob]

Boxer, My point was there are consequences when limited experience meets up with expensive equipment requiring proper techniques. Taken from movie lines, some say: "A man's gott'a do what a man's gott'a do". Others say: "A man gots ta know his limitations".


Dave, Looking at this pic I see female threads that are good in the inboard steel insert part (rear 5 threads), but messed up in the low strength Aluminum casting (front 5 threads) that contains it. Those Aluminum threads aren't critical to the holding power strength of the joint, but because of Aluminum's softness must be there merely for alignment. That means you are in luck and won't have to get a tap. Using my method described way above will straighten out those crossed Aluminum threads. You see little damage on the steel pin bolt's threads, but massive damage on the Aluminum threads it mated with. What was done can be UNdone. (text continues below)




BTW, I just keyed your hometown of Wingina, VA into my GPS and the 455 miles & 7Hr33Min route came out. That would be an overnite and I don't think you need me that bad. Towerworker is too modest about his abilities.

I see in-thread residues of the (Green) threadlocker the Germans have used. Ruddy is correct about creating a thread chaser from the part with an acute angle file. A really good chaser can made using a Dremel cutoff wheel making 4 equal spaced slots at a tilted angle so it "cuts & scoops" the material. BTDT for a sparkplug thread hole repair, using a sparkplug. Rather than weaken/destroy the pinbolt by making it a thread chaser . . . . and being the damaged portion is Aluminum, I'd try my oiled up reverse direction thread forging method first.

[Boxer]

That would be an overnite and I don't think you need me that bad.

I can vouch for his overnight accomodations. They are excellent! And free.

After reading through my Haynes manual I think I would have taken off the rear wheel and removed the lower shock bolt after placing some support underneath the swingarm & FD. The book also says to put a chunk of wood in between the swingarm and the transmission housing to keep it from dropping down on top of the drive shaft.

[towerworker]

I have said this before but it bears saying again:

We are all extremely fortunate (blessed?) to have CycleRob on this board.

His knowledge, experience and expertise (not to mention willingness to help) is a very rare thing indeed.

Again I am willing to help in any way that I can and I agree with CycleRob in that "a little knowledge is a dangerous thing". I vote with him that we should do this by his instruction and if I can help I will be most glad to.

Also -- maybe I am not up on all the recommended services and maintenance items.............this adjustment you were starting.........is this a necessary thing and what were the indications that had you think it was needed?

Wayne

[Boxer]

I think David may be at work right now and I can't guess his intentions, but it sounds like he was trying to check the play in the swingarm pivots and decided to just pull it off to lube the output shaft splines.

[towerworker]

Another note----Can I safely assume that to perform CycleRob's procedure the entire swingarm assembly needs to be removed so as to be able to run the bolt in from the inside?

I'm a little slow...........but I get faster!

Wayne

[Beemeridian]

22

[maduko]

Sorry if this has already been mentioned...

Invaluable tool for repairing internal threads is a nigfty thing called a thread file. I have two of them and one has ends that are made to chase internal threads. Thread files correspond to the thread pitch- the diameter is not a problem.

I think mine was made by Hazet or Wurth? Here's the only link I could find with a picture...

http://www.thepartsbin.com/cartools/spe ... nal-d.html

HTH

[Arbreacames]

there are a couple of things I do not understand after reading the shop manual;

• On page 33.5 (228) of the shop manual there is a Note "Note inner races of needle bearings"
  Anyone know what that means?
  
  On page 33.17 (240) it says ∆! "Make sure that the inner race never presses against the ends of the needles"

Dave,
The two odd-shaped bolts that you removed from both sides of the swingarm are the inner races, i.e., they are the surfaces over which the pins roll. The manual is telling you 1) to make sure that they are not indented by wear, and 2) to make sure that when you thread these "bolts" in, that you do not push against the end (point) of a needle or you'll destroy the bearing.

I don't understand why there was an "upward force" between swingarm and bolt. Could it be that you performed the operation without removing the wheel? Then the eccentric weight of the wheel would have torqued the FD until the bolt was out.