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Old 09-19-2012, 12:18 PM   #46
rebelpacket OP
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Originally Posted by disston View Post
Need new rubber pieces nobodies surprised there. The real question is do you feel up to removing the clutch for checking and then the flywheel to look at the rear seal. After you have the trans out you should be able to make a better informed decision. There are several extra tools to get into the clutch and install a rear seal but we'll cover all that if needed later.
I'm up for whatever needs to be done to get this bike into a reliable runner. I'm not bead-blasting the frame, or scrubbing the engine case, but I'll buy some tools and dive deeper if there is something wrong.

I agree with you that given the water rusty sludge, its worth checking and lubing the splines at the very least. Snowbum (http://bmwmotorcycletech.info/clutch.htm) also mentions that excessive lateral play in the transmission output shaft is worth checking as well, I guess. I don't think Kait will be too thrilled with me baking my transmission in our oven though... I'll buy her flowers.

So, my biggest question on transmission removal, is the pushrod. Is there enough clearance when removing the transmission that a good firm yank backwards and out through the kickstart side, and everything will clear? The manual doesn't really show how much the input shaft/pushrod protrudes.
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Old 09-19-2012, 12:38 PM   #47
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The rod doesn't protrude that much, very little in fact. Unbolt at four corners, try to keep bolts and nuts and washers together. Each corner is different and has a specific arraignment for attachment. Pull trans back and remove to left side. It's almost a natural movement. One person operation most of the time. You can use some painters tape on frame rail if it's handy or rags. Not a big deal. Most don't cause any damage. Before you put it back together touch up a little with black paint. This will look better than the rust spots after two weeks.

I have never been to the bother of repainting my frame or polishing the cases. But I try to keep rust off stuff and I clean a little now and then. It's more important to me how it runs. And I don't have any leaks. If I do I get to them when I can. That might be next Winter. But I've never had that many.

You have a 4 speed trannie? I'm a 5 speed guy. How many miles on trans? If you know. Transmission repair is usually something we recommend you send out although the more advanced and sometimes more maniacal of us do our own.

After you show us some fotos of the front of the trans and the area under the clutch/flywheel area we can tell you more.
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Old 09-19-2012, 03:46 PM   #48
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Well, I'm happy to report it looks like the input splines have been well taken care of.



There doesn't appear to be a nice puddle of oil under the clutch, or signs of drips.



The input shaft on the transmission had a nice thin coat of what looks (and tastes) like Honda Moly. There is a build up of what looks like clutch material and some of it is a little wet. It doesn't look like anything was leaking profusely, but I don't know.



Again, the splines look real good in my uneducated opinon:



The BAD NEWS came from the drain plug. I'm not too familiar with Airhead transmissions, but when a bronze paste along with some slivery chunky bits come out, I worry a little bit. Maybe a bushing and bearing are disintegrating? Maybe this is normal wear?


(Pencil screwdrive for scale)
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Old 09-19-2012, 04:11 PM   #49
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Everything looks really great till you get to the debris from the drain plug. Which drain plug? I guess you mean the transmission. That does not look normal in any fashion to me but like I said I'm a 5 speed guy. I don't know exactly what it might be. Some kind of bushing sounds like a good guess to me.

You have not ridden this bike yet have you?
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Old 09-19-2012, 05:34 PM   #50
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Dropped a note to Anton. I'm not sure if he's still rebuilding transmissions for customers or not.

Anyone have any /5 transmission experts they'd recommend for a rebuild. On closer inspection, its a half/half mix of chrome patches and tiny slivers of steel. I think the bronze color might be from oil? Either way, I'm not putting this transmission on the bike and riding into the sunset just yet.

Two steps forward, three steps back!
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Old 09-19-2012, 07:46 PM   #51
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Pretty sure Anton is doing transmissions.

You may want to pick up another trans also. I'm a proponent of the two transmission Airhead theory. Nothing wrong with having two so you can be riding one while the other is fixed. So you can use a 5 speed in the /5 if it is one of the Long Input Shaft five speeds. They are 1974 through 1980.
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Old 09-20-2012, 11:33 AM   #52
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I got real lucky!

I reached out to Matt Parkhouse, BMW tech extraordinaire here in CO Springs about rebuilding my transmission. I'm going to order replacement bearings, seals and gaskets and bring it over to him.

Hopefully I'll get to put on my student hat and watch him do his magic. Maybe understand more clearly how things in there work, and how they wear.
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Old 09-20-2012, 11:54 AM   #53
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Be interesting if you can photo and report what Matt says is the cause of this. Matt did a transmission rebuild article a couple years ago I think in the Owners News. I'm not sure but think that was a 5 speed so maybe he could do the 4 speed now?
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Old 09-20-2012, 01:02 PM   #54
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I got real lucky!

I reached out to Matt Parkhouse, BMW tech extraordinaire here in CO Springs about rebuilding my transmission. I'm going to order replacement bearings, seals and gaskets and bring it over to him.

Hopefully I'll get to put on my student hat and watch him do his magic. Maybe understand more clearly how things in there work, and how they wear.
He's very experienced and really knows his stuff. It's always a better idea to have a guy nearby do it for you.
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Old 10-04-2012, 10:56 PM   #55
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Good news! I met up with Matt Parkhouse with my transmission, and he went through it with me bit by bit.



A -huge- photo dump and a write-up of the experience is coming soon. I'm very grateful for Matt's time and work. He works very smoothly, like its walking, or breathing. I learned a tremendous amount in the three hours Matt let me watch him work.
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Old 10-05-2012, 09:20 AM   #56
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Can't wait.
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Old 10-05-2012, 01:56 PM   #57
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Warning: This post is fill with photos. I apologize if it gets lengthy.

Matt Parkhouse is a legendary BMW guy. I won't list all of his accomplishments in detail here. Suffice to say, he is what I would call an "Old Master". One of those guys that gives you 2 years of knowledge in about 30 minutes of talk.

I stopped by his shop with my /5 transmission securely bungeed into the sidecar of my Ural. After introductions and expelling the virtues of crappy soviet machining, we started work on the transmission.


Matt bolted up the transmission to his stand, and immediately got to work with two propane torches. What usually takes me 5-10 minutes with a heat gun, took him 30 seconds.


Actuating the kickstarter at about 40 degrees with some persuasive rubber mallot taps, and the cover comes free.


Having never seen one of these in the flesh, its nice and compact. Neato.


The bolt your are looking at in the center of the picture is the eccentric for the "top" shift fork.
The line on it indicates its current position. Matt noted this and drew a simple diagram recording its position.
He did the same thing for the "bottom" shift fork eccentric, before removing them. He marked the shift forks with top or bottom and kept the eccentrics with each one.


More quality time with propane torches. Again in about 30 seconds the housing was hot enough to remove the shafts


"No two forces greater than gravity and inertia" Matt said, as he picked the housing up and held it over the floor. Holding the side of the hot housing, suspended over the floor he gave the lower portion of the housing a couple solid whacks. The three shafts puked out of the gearbox like a college student on spring break.


Surprisingly, all the shafts looked very good. There are two bronze bushings under first and fourth gear on output shaft. Considering the color of the metallic paste I pulled from the drainplug, I expected to find them disintegrated. Matt used a handy press made from recycled railroad materials and popped off 1st and 4th gear, along with their bearings.

In another surprise, both bushings we're in good shape. No significant wear or scoring. One of the bearings on the output shaft was a little notchy, and a bearing on the intermediate shaft didn't feel 100% either. Matt pressed them off, and pressed on the new bearings.

Both output and input seals we're not leaking and in good shape. We took them out and replaced them with new ones. I'll file the old ones away for emergency spares.

Onto re-assembly.


This is a cut-away corner of an old transmission housing that matt uses to hold the output shaft into place while he aligns the shift forks.


With only the output shaft, and the shift forks in, Matt uses dental mirrors and a flashlight to align the shift forks on the shift sleeves. He turns the eccentric until they are "dead center" on the shift sleeves.


He snugs them up, and double-checks the alignment with the flashlight and dental mirror. He then noted the new position of the line on each of the shift fork eccentrics next to the original. The old setting was off by about 1/8th of a turn on the eccentric.


Next, Matt measured for the all important shimming. He heated the housing up again with the torches, and dropped in the output and intermediate shafts. Then he used two flat bars and a depth micrometer to measure to the bearings outer races in multiple areas, multiple times, recording his measurements.


Followed by measuring the depth of the bearing races on the transmission cover.


Then, he calculated the shims for the output and intermediate shafts. The spec is for .05-.10mm. Matt said that he prefers to stick to the loose end of the spectrum. We ended up with .08 on the intermediate shaft using two shims totaling .58mm. Got a solid .10mm on the output shaft using a .30mm shim.

This was always the worrying part for me, and Matt made it simple. Other than the tool needed to hold the output shaft in place while aligning the shift forks, I don't think you need any special tools (other than some flat bar and a depth micrometer). The way he did it was quick, accurate and simple.



This last part was a bit of wizardry I wasn't able to capture on film. It took Matt only two tries. I think it would have taken me close to 20. Each time, matt threw all three shafts in the freezer and heated up the housing.

Through some miracle of mechanical dexterity, he held the output and intermediate shaft together, as well as the shift forks in the shift sleeves, and dropped the cold shafts into the hot transmission housing. He mentioned that you have a "very, very small" window of maybe a minute to get them in before they won't go in. If you don't get it in, don't fight it. Put it back in the freezer, fire up the torches and give it another go in another couple of minutes.

With all the shafts back in the transmission, he heated up the transmission cover with the torches, and again depressing the kickstarter about 30 degrees, maneuvered the cover in place over the shafts and shims.

And that was it! His rate for the work was very fair, especially given all the questions he answered for me. If I ever need to break open my transmission, I won't hesitate to do it next time around. I know it'll take me much longer to do than Matt, but the aurora of mystery is gone. I immediately started scribbling down notes from memory when I got home so it doesn't fade.

This morning I put the transmission back into the bike and started putting the swingarm and rear end back on. I think I might just be riding in time for my 30th birthday after all.
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Old 10-05-2012, 06:13 PM   #58
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Thanks for posting that! Do you mind if I ask how much he charged?
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Old 10-05-2012, 07:18 PM   #59
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Rebelpacket,

That is a really good job of reporting. A great story and so nice to see a master like Matt Parkhouse at work doing what he likes and what he does so well.

But there was no answer to the question of what was the Bronze stuff that came out with the oil of your trans?
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Old 10-06-2012, 01:23 PM   #60
rebelpacket OP
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But there was no answer to the question of what was the Bronze stuff that came out with the oil of your trans?
Charlie,

Unfortunately, we don't have a "smoking gun" so to speak. The bronze coloring that was on the drain plug, was also seen on a bearing cages of two bearings that we replaced. My guess (and its only a guess at this point) is that the bearing faces we're in a state of semi-rust or something equivalent.

The flakes and coloring (I'm guessing) are from that, considering that the bronze bushings we're in such good shape.
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