R62 Project: The Beginning

[bmwmyplace]

Hey Peter as I have an R17 I am most interested in the answer, or was it anwsered somewhere else Regards Peter G

[schrader7032]

I searched the forum for "DM 175" and came up with these posts...

http://vintagebmw.org/forums/viewtopic. ... hlight=175

Kurt in S.A.

[bmwmyplace]

Thanks Kurt thats great ...Peter

[pierce7221]

Both the R12 and the R52 I've worked on had been pretty buggered up by the DPOs. (DPO stands for Darling Previous Owner.)
wowie. i thought i had trouble with my R50's DPO (made a thread on another forum just to complain about him), but it's nothing compared to this. i've always loved the style of those ancient models with the gas tank on the inside of the frame. good luck 8)

[VBMWMO]

As if I didn't have enough bike stuff going on right now.

I mean, I've got two complete Beamers apart in my garage. Well, sort of. The bottom end of the R12 is in Germany. And the R12 frame and the R51/3 frames are all out to The Frame Man getting straightened. (Yes, that was plural; I'm making one good frame out of two bent R51/3 frames).

So, when my friend Scott told me about an R62 drivetrain he was thinking of buying, and showed me the pictures he had, I was interested but secretly happy that he was getting it.

Then he told me he had bought it and it was being shipped. The story was that he got it from the former son-in-law of a guy who had bought the bike in 1954 to use to power a "wind boat". He had taken the drive train from the bike - the gas tank, motor, transmission and drive shaft - and thrown away the rest. I was horrified, but Scott had apparently already asked about the rest. Of course, in 1954, the bike was just a 25 year old bike that nobody wanted.





Fast forward a few weeks. Scott tells me that the boxes arrived. Then he mentions to me that he's sorry he bought the thing because he's got too much stuff and needs to unload it. He hasn't even opened the box with the motor yet. Am I still interested in it? Sigh. Of course I am. So we make the deal, and I carry home the boxes.

In one box is the gas tank. It's gray, mostly, and in pretty good shape, even including one chipped roundel. In another box is the gearbox, opened and with a bag of parts, the two heads from the motor, and the intake manifold, with an Ehrenfeld slide carburetor attached. The transmission turns, and by fitting the top with the shift lever, I can shift into all three gears and two neutrals.

The engine is a horror. None of the packing has been, what you might call, careful. But the motor was basically thrown in a box loose, with no care at all, and hardly any cushioning material. The case is cracked dramatically around the bell housing and both cylinders have big bites taken out of the outside fins, pieces of which I eventually find at the bottom of the box.





I spent about an hour doing the jigsaw puzzle, figuring out where the pieces fit in, all the while cursing the idiot son-in-law and imagining what the welding charge is going to be for this. What started out as a pretty darn good deal on the basis of a project has very quickly started to look like a mistake.




The motor itself was frozen, with the pistons at BDC and a valve on each side open. This is an annoying situation if the pistons are really stuck in the bores, because pounding on them won't really do any good and will just be beating directly on the crank.

So, I start in disassembling things to get an idea of what it's like inside. Remove the 4 cylinder base nuts on each side -- well, the 3 nuts on the right side. I wonder where the fourth went. Not all of the nuts are particularly tight, either. They're all the original style nuts, however. Oops, don't forget to remove the valve covers on top of the cylinders and remove the fifth base nut that's inside there!

Surprisingly, the cylinders both come off easily. But the crank still won't turn. I guess I have to go deeper.

I remove the 10 or 12 nuts that hold the engine cases together. I remember to remove the 24mm allen key plug on the top left side, under which is the oil pump quill shaft -- driven by a worm gear on the back end of the camshaft -- and remove it.

The cases don't want to separate easily, so I start tapping it with my plastic mallet. Slowly it comes apart.

Inside the crankshaft is revealed. Everything is covered with dried sludge. Now that I can put my hands on the flywheel, the crank will turn with a struggle. I shoot some TriFlow into the bearings and move the crank back and forth, but it doesn't loosen up.

So, I start to work removing the pistons. The pins come out with light taps on the end of a 1/4" drive ratchet extension.

While I'm working on the first one, I notice that a part of the skirt is missing, and a bit sharp. Also, both pistons are of a type that has the skirt split on one side. I've been told that these are not high quality replacements, because instead of figuring out the correct expansion, the split takes it up.

Suddenly, the crank moves freely in its bearings, and the end of my left ring finger gets caught between the sharp edge on the piston skirt and the case. Yow!! I have just grabbed a (clean) rag and am holding my hand above my head when my cell phone rings... It's in my left pants pocket... I manage to retrieve it with my right hand and flip it open... It's my wife, have I forgotten we're meeting a friend for dinner? "Well, I'm a bit tied up right now, Honey... I guess I'm going to miss it."

The bleeding slows and I finish up removing the pistons (while clenching the rag).

The crank now moves easily and smoothly. At last, there's some kind of success!

I unlodge the main bearing housings from the bottom crankcase half and lift out the crank and flywheel/clutch assembly. Actually, this looks pretty good. In fact, I can see that nobody has ever messed with this crank before! This is practically gold! Both the R12 and the R52 I've worked on had been pretty buggered up by the DPOs. (DPO stands for Darling Previous Owner.) But not only is the original crank pin visible -- because the face of the web and the pin were surfaced after assembly and the two locking pins that BMW inserted into holes drilled into the seam of the crank pin with the web are still there -- now I can also see that the crank web has the actual motor number stamped in it!!




Now, this isn't definitive, but in my excitement, I swing the connecting rods to one side of the crank, so their small end holes line up, and hold them, while trying to push and pull against them. I can't feel any movement. If that should prove to be the case once the bearings are cleaned, the crank won't have to come apart. That might balance out the cost of having all the welding done!

Here's a few more shots of the motor. Notice that the bottom case and both cylinders are stamped with the motor number. The pistons may not be original, but everything else is!









This is really great! I'm now very excited about this, but as I'm going to be out of town, I now will have to wait to do more work on the motor. I'll write more about this as I make progress.