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Old 02-21-2009, 05:42 PM   #1
mark1305 OP
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A Tale Of Two Transmissions - Airhead Style

OK, I promised/threatened to start this thread with the catchy title a couple of weeks back. Time has come to get it launched even though there is still some work to be done.

Background: In November, 2007 I bought a very nice 1983 R80 ST. Paid a somewhat premium price (not unreasonable) for a low mileage (34K miles) bike in very much unmolested condition other than a good quality repaint in the original red color and the tank had been professionally cleaned and relined, all by the second owner most likely. I bought it from the third owner who had bought it in Ohio, flew up and rode it back to the Tampa area in Spring of 2007. He was selling off a collection of BMWs as part of a lifestyle change. I test rode the bike thoroughly and was happy with it. An interesting side note: one of the POs had compiled several 3-ring binders full of every airhead tech article and airhead mailing list message all sorted by topic - just no receipts or notes as to what may have been actually done to the bike.

I rode it for many more hundreds of miles, including entering it into the Riding Into History show in St Augustine in May 2008. Soon after that I started to hear the dreaded gear whine from the transmission in all 5 gears.

After consulting much of the collective wisdom here and a few other well known internet sources, there was nothing to do but park the bike until the gearbox could be opened. That drug out through the summer of 2008 until I could fabricate a flange puller and block out the time to do it in the Fall. Probably early October I opened it up and immediately noticed tell tale signs that the transmission had sat with water in the oil for some period of time. The net result was that several matched gears were pitted halfway round their circumference indicating the bike was merely sitting for a long period not racking up miles. NOTE: So much for low mileage bikes - there can be demons lurking in that low mileage status.

I contacted Anton Largiader and had several productive discussions with him about what I observed in the transmission. In the end, I sent it to him for a more experienced opinion. At first it looked salvagable, but as Anton got deeper into diassembly and cleaning it became apparent that fixing the transmission to anything near satisfactory would likely be economically not feasible. Dealing with Anton was a great help, as I had opened and inspected the transmission myself. Then getting his insights into what I saw and what we had to deal with was as good as taking a vo-tech class. We ended up agreeing to send all the parts back to me for my continuing education in 5-speed boxes. Dealing with Anton was a pleasure and a real learning experience for me.

Next step was to gamble on an Ebay 5-speed from an established BMW parts breaker. Scored one for a reasonable price that was supposedly from an '84 R100 with nearly the same mileage as my R80. It looked good. Was a bitch getting the output flange off compared to the first tranny, but that's material for another whole thread sometime.

Got the flange out and my heart sank - a big spot of bright red rust on one spot where the output bearing and shims sat. Not another water damaged transmission I thought to myself. Actually, not. I pulled the rear cover and found only one more small spot of bright red rust on one gear cluster inside the box. It appeared all of it was new flash rust that had occurred from a small spash of water that probably got in through the speedo drive after the bike was stripped for parts. It all cleaned right off with no pits.

Checked all the bearings and found just what I expected for a 34-35K mile transmission - output shaft bearings very loose, one or two others headed that way. Good news! the first gear and fifth gear were in great shape on the shaft with very little axial play compared to the original transmission.

Nothing to do but the standard bearings and seals R & R and put it back in service after a thorough cleaning.

Oh yeah, the circlip issue. This transmission did not have a circlip, but had the groove in the shaft. Hallelujah!


So ends the first installment of this tale. Pictures are to be uploaded shortly and added in here soon.

Once again, full credit to Joerg and his excellent page on the 5-speed overhaul and also to Anton for taking the time to go over what we both observed in this transmission.

Stay tuned.
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Old 02-21-2009, 06:16 PM   #2
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Anton really is great to work with.

And I hope I have a long way to go before I find out as much as you now know about transmisisons
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Old 02-21-2009, 07:26 PM   #3
datchew
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Anton really is great to work with.

And I hope I have a long way to go before I find out as much as you now know about transmisisons
+1 on the first. On the second, I've resigned myself to endeavor to NOT learn anymore about gearbox internals. I think i'm at that point where I'll just send stuff like this out for now. Good man Mark for diving into the guts at that level.
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Old 02-21-2009, 08:09 PM   #4
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I've uploaded some pics to Smugmug, but I'm calling it a night for right now.

But one of the pics I want to show is how simple the transmission looks when laid out in the order everything goes together - that's the key. I dabbled with Ducati transmissions on a couple of bikes. They are a lot easier to shim, but you really don't want to disassemble the gears & shafts because of more internal shims and spacers than the BMW box ever dreamed about.

More BMW pics tomorrow. Promise.
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Old 02-22-2009, 06:55 AM   #5
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Back To The Tale...

I wanted to keep the bike a "roller" for moving it around my crowded shop (one car garage holds 2 BMWs and a Town Car every night).




Home made flange puller from 5/16" plate with the tab on one end for a 1" pipe to slip on as a handle.

It worked great - this time. More on it later


Doesn't look too bad, so far...



The oil was clear of water when I bought the bike, and I changed it out myself when I brought it home. But look what is visible deep inside the box:


Looks like high-water marks, don't it? Not surprisingly, several gears had pitting halfway round their circumferences just about matching the oil/water level marks.

Good side:


Bad side:



Hhmmm... Low mileage, high corrosion transmission.
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Old 02-22-2009, 07:46 AM   #6
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But Wait; There's More

I've played around with a few Ducati transmissions, which are pretty robust and almost never see corrosion or pitting, so I'm in unfamiliar territory now. I give the pitted areas the old skool fingernail test. I can feel them, which is a bad sign. I also feel more wobble on the shaft at the first gear than I'm comfortable with. Thus started the dialog with Anton and my transmission winning an all expense paid vacation to Virginia.

At first we thought the box was repairable, but as Anton began completely stripping and cleaning parts he found too many bits that needed attention or replacement. We kicked some ideas back and forth, until I decided to cut my losses on that transmission and find a replacement. I gladly paid Anton for the bench time spent on it and had him send it all back to me. The knowledge I gained just working with him over the phone after havng inspected the box myself was worth the price of admission.

So, Ebay to the rescue. Picked up what was listed as a box from an 84 R100 with roughly the same 34K miles as my R80 ST. Cheaper by more than half of what just parts would have cost for the original transmission.


The flange puller revisited - The first time, it worked a charm. On this "new" transmission, the sides just bent up like butter when I put the pressure on the 2-jaw puller. A few minutes flattening it ans squaring it up again on the hydraulic press and it looked good as new. Then a little beef added to make it better than new...

The zip tie holds 4 eliptically ground washers that stand the puller off the edge of the case where the drive shaft boot goes. If I ever get around to making a face plate for the lathe, I'll just cut a relief on that side and be done with keeping trackof the washers.

First peek inside. You can see the spot of rust on the output bearing that scared Hell out of me when I first popped the flange out.


The rust turned out to be relatively fresh and mostly confined to the shim stack - the edge of the bearing was hardly etched at all.

Always label your shims as you pick them off the bearings.


Look Ma! No high water marks, like before! You can see the only other rust spot - bright red and very fresh looking on just two gear teeth and no pitting underneath. The condition of the gasket and green Loctite on the shifter bolts makes me believe this box has never been opened for service.


Weird aluminum oxide deposits around the drain plug indicate there has been at least some chemical intereaction between the ferrous metal fuzz on the drain plug magnet and surrounding aluminum. Easily cleaned.

Notice anything missing?



Everthing laid out in its general order and ready for the basic overhaul - bearings and seals and a good cleaning.




Overall all the components in this transmission look fresher and less worn than the original. However the time is just right for overhauling. Both output shaft bearings can be wobbled a few mm, with the 6403 being really loose, as can be expcted. All the others are just loose enough that you woudn't want to leave them in even though they probably have more miles left in them.

My BMW dealer couldn't get me the gasket/seal set complete for the "older" models like mine, and the paralever kits are about $20 more beause of the output seal mainly. I got the gasket set from Hucky's down in Vero Beach. Hans is a great person to deal with. Bearings came from my local bearing jobber, and I ordered the "1.00mm Cover" from BMW - it's the one that if your press blocks slip while pulling the bearing from the input shaft, it gets a little dinged. I could have reused the one I dinged, but best practice is simply put a new on one under the new bearing.

Lastly, a couple gratuitous shots of the shim tool coming together...





Today's agenda should include cleaning all remaining parts, pressing bearings off and back on, and maybe getting as far as discovering which one single shim I'll need but not have on hand


Stay tuned.
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Old 02-22-2009, 08:16 AM   #7
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Originally Posted by mark1305
Lastly, a couple gratuitous shots of the shim tool coming together...


Is this your HF mini-lathe?? Looks like you are still receiving satisfaction, eh? I was reading up on lathe's last night and one of your old posts sent me flying through the web on a magic carpet of information. Thanks for that.


Nice write up + pics mark. What causes the gear wine in the first place?
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Old 02-22-2009, 08:43 AM   #8
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Thanks BW. The HF 5980 is working out OK. The more I play with it, the more I understand tooling and setup is about 90% of machining operations.

The lathe side lacks thread cutting capabilty (no power feed), but 99% of thread cutting can be done using a tap or die holder in the tailstock or milling head and feed with one hand while rotating the tool or workpiece by hand. End result is still accurate threads.

For production work, it lacks some features. But for one-off dabbling and precision repair stuff, it's very handy.

Using the thick Lexan stock for the shim tool was poo-pooed by some as not rigid enough. It is very easy material to mill, so I gave it a shot and found that the finished plate takes several lbs of pressure in the center to deflect .001" on a dial indicator. I don't think my depth guage will exert more than an ounce at most. The real learning curve centered around the fact that the milling head is not height adjustable. So a set of stackable spacers to go under the milling vice (with perfectly parallel surfaces of course) cure the problems with thin workpieces that the quill won't quite get the end mill to reach. On the other hand, I wanted to true the edges of that shim tool with end mills, but it is too wide in any dimension to fit under the end mill. The future cure for that will be a tooling plate that can be mounted directly to the cross slide and stand vertically for workpieces to be clamped to it. That gives the capability (hopefully) to fit a workpiece in using all the space between the top of the cross slide or even hanging it off the edge of the slide to use the space right down to the ways.

The more I read machinists handbooks, the more I feel like I have weaker problem solving skills than I ever realized. There are so many solutions that are so simple, yet so genius.

Oh yeah, almost forgot. In addition to the shim tool, I milled a huge depth guage stop for the depth end of my digital caliper. I have a couple more cuts to make on it. But it will effectively be a big bridge of a known height that spans the gasket surfaces of the trans case and will read the height of the bearing directly, then do the same for the recesses in the cover. I want to compare the measurements between the two types of tools. Maybe I will have created a simpler shim tool with as good accuracy - or not. But it will be an interesting experiment.
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Old 02-22-2009, 08:09 PM   #9
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I am a little lost, but loving this, I dont know why.
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Old 02-23-2009, 03:22 AM   #10
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Great thread. Thanks for sharing. Love the lexan idea.
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Old 02-23-2009, 12:24 PM   #11
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Sorry, but no update yet today. Yet...

Yesterday cleaning the case & cover took longer than I anticipated and I had to knock off to clean up and sacrifice some steak and shrimp on the grill.

Today as I was just about ready to finish cleaning gear shafts and swap out bearings I got sidetracked helping my neighbor out of a mechanical dilemma. He was addressing an oil leak where the 90 degree oil filter adapter on his Jeep Cherokee mated to the crankcase. The dealership explained to him that normal procedure is to jack the engine up off the mounts to fit the huge Torx bit into the adapter. But the mechanic described to him how to cut down the Torx bit and weld a handle on it to avoid raising the engine. So not only was it the neighborly thing to drop what I was doing to help out, I love a challenge that involves metal mangling.

Long story short, the tool mod worked a charm and my neighbor discovered some knuckle head before him had installed the adapter without the outer o-ring Another problem solved.

With luck I may get to the gear shafts this evening, if not, then tomorrow. I'm itching to get this thing back together and practice some shimming skills.
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Old 02-23-2009, 04:41 PM   #12
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Yea, we need more blood and guts!!!!. Love those internal picts.


I don't know if i am more jealous of the fact you can make stuff out of metal, or that you had BBQ when its 25 degrees up here.
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Old 02-23-2009, 04:55 PM   #13
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Learning a lot

Mark:

Love your thread and the pictures. Being a visual person I have to learn what's going on by seeing it. Your pics are outstanding. Will watch this to the end.

Tom
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Old 02-23-2009, 05:43 PM   #14
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Yea, we need more blood and guts!!!!. Love those internal picts.
+1

Mark, I've always wanted a tour of the gearbox guts. Great idea on the lexan and it sounds like you tested the deflection enough to convince yourself. If it works, it's a solution. Maybe i will take a poke at my gearbox someday afterall.

Watching with great interest.
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Old 02-23-2009, 06:06 PM   #15
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What I would give to be an apprentice

...of some of you guys. Man, the knowledge/skill I see out there is phenomenal.

Keep it up! Very inspiring. Cool project.
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