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Thread: My 1974 R90/6 never-ending project, with plenty of pics.

  1. #1

    My 1974 R90/6 never-ending project, with plenty of pics.

    If any of you out there put 2 and 2 together, Im the one who wrote the My Turn on the January ON. I wrote the article in Like October, when work was still progressing on this bike, but a year later, I havent had much time to get things further.

    I figure its time to put together a thread about my second BMW, the R90 project. This is a mechanical pursuit, cosmetics will come years (haha) later.

    This will bring you from the beginning up to now.

    For those of you who dont feel like finding the old issue, Im 22 years old. Ive been with the same lawncare business for 10 years, and owned it from April 2004 to August 2008. I just sold it to my brother, one of the original owners, as I have moved off for Missouri University of Science & Technology (after taking 89 credit hours at the community college) for a major in Aerospace engineering, and minors in Explosives Engineering and Math.

    One of my lawncare customers is/was a great guy, real talkative, real smart.

    In 2004, I noticed these two strange motorcycle shapes in his garage, hidden behind some boxes. Turns out, BMW makes motorcycles.. and we worked out a deal on his wifes bike. It had been sitting since about 1981, with gas in the tank, covered in cat urine, and all kinds of little demons here and there. I don't have any before pics, because I'm an idiot, but here is how she looks after a bit of money and work:

    Here's where I rescued it from:

    ..and ever since the day I got the R75, I had been dreaming of the R90 still sitting in there (YES, there IS a motorcycle in this picture):

    I kept mentioning to him that I REALLY wouldn't mind taking on another project.. but he was very reluctant, after all this was his personal bike. His excuses included that he couldn't be in the BMW clubs if he gets rid of it. But, he hadn't ridden the thing since ~1981, so I was a bit anxious.

  2. #2
    Well after 2.5 years of consistent reminding, on June 11, 2007 he came outside while I was cutting his grass. He asked if I was still interested in it.. I lit up.

    Sadly for me, he said that the guy who just remodeled his house said he'd buy it for $1200 cash.

    Ugh. That's a bit high of a price for the condition, I thought. I got to thinking about it, and I figured what-the-hell..

    I told him I'd give him $1000 that day. He said $1100, (which he needed as downpayment on his new BMW R1200RT)!). I told him I'd get it to him by next Monday.
    He said he wanted the bike gone, out of sight, so when the remodeler comes around, the bike wouldn’t be there any more.

    I decided to cut my work day short, so 2 hours later, and:

    Here are some detailed shots:

    ..and here's the loot:

    The bike, the bags... fairing lowers, 2 complete headlight assemblies, the stock gas tank (in great shape), new-in-box bulbs and filters and oil pan, extra mirror, extra turn signal housing, BMW crash bars, random old motorcycle literature, and some other odds-n-ends.

    I reunited the two bikes:

    The happy new owner:

    Its new home:

    A mini-tear-down begins:

    I started doing a minor tear-down/preparation. Whilst performing the last step of the day - an engine oil change – the old style rubber o-ring that goes between the filter and the 'cap' (which on newer filters is now built in) slipped out of my oily fingers and down into the block/pan. Well, what do I do? I was talking to my moms... boyfriend-guy-whatever, and he said he'd just go on with the project and start 'er right up. I personally didn't think it's a good idea.

    So, fearing what I might find, I dropped the pan and cleaned things out a bit.
    Last edited by crazydrummerdude; 10-02-2008 at 04:37 PM.

  3. #3
    After waiting months(?!) for a damn oil pan gasket to arrive, it showed up and it was time to put together my R90 and see if I could get it to turn over. It needs a full overhaul, but I am a broke(!) dumb kid and I have too many other projects going on right now.

    Well, I decided to actually follow the recommendations of people who dont know these bikes, and used gasket sealer. I really didnt need to.

    The Clymer said to tighten the bolts "securely." Well, what does that mean? I like actual numbers, so I guessed and made corrections to a torque wrench to get to a "secure" feel. Right as I approached it.. THWACK! There goes one of the bolts. ARGH!

    I freaking took all the 13 other bolts out, dropped the pan, but ah ha! Good luck, a lot of the bolt was still sticking out, and even better... I could unscrew it with my fingers. So, it all went back together.

    I filled it up with oil while I was installing the carbs.

    I hooked it up to a battery charger, and got the starter button to work finally. But, I heard crackcrackcrackcrackcrack when I press it. Hmm.. did it seize up? I am pretty sure I could turn 'er over with the kick start. So, I try the kick start. It's not going ANYWHERE. Damn it. So, I pull the clutch and try the starter button. Now it's just bogging down instead of crackalacking. It's still not turning over. So, I pull the clutch and the kickstarter can swing down now, too.. but that doesn't turn it over, and there's little-to-no recoil. Damn. Transmission problems too. So, I figure I'll just bite the bullet and remove the transmission. A nut holding down the battery box is so stripped and rusted, I have to remove that mount with the box. I use my own judgement, and a little bit of the Clymer, on how to get the transmission off. In the procress, I also noticed this crack. It doesn't actually turn right again (as the picture looks); it just runs along the "grain" for an inch. Damn.

    I was trying my tools on those output bolts, but they weren't budging.

    Well, it was getting late and I had reached a stopping point on my project, so I looked for something else to do for a bit.

    Ah ha! Why not make my own modified 27mm swingarm socket? Screw buying one.

    I turned this:

    Into this:

    I made a boo-boo on my original mental design, but I knurled it just for show (and screwed that up, too, haha).

    ..and it (barely) fits!

  4. #4
    The next time I worked on it:

    I went for the transmission. I was pushing a little beyond my comfort level, but I got it disconnected.

    At the time, this was the furthest I've ever gone with one of my BMW's.

    Ignore the dirt/grease.. the splines are good.

    What cracked the back panel is the fact that the u-joint mount on the output shaft is totally wobbly. It ground away at the inside of the circle area. Shavings/etc can be seen.

    ..and caused this (to the swing arm where the driveshaft goes):

    We got to looking more closely, and we nocited the transmission case had been welded, and machined down around the kickstarter.

    So, next step is to get to the real engine dirtywork.

    At this point, I started to think that the previous owner forgot to mention a few things... but, honestly, I don't really care.. it could be a lot worse for a barn find. I will just learn a lot more with bringing-back-to-life this R90 than I did with my R75 (which is my daily driver).

  5. #5
    Ok, so the way I understand it the u-joint mount is pressed onto the output shaft and secured onto it by one nut.

    It is this nut that has come loose, causing the u-joint to fling around and mess everything up.

    Since the u-joint is no longer secured to the output shaft of the transmission, the back wheel can roll regardless of whether the engine is stuck and/or the transmission is in gear or neutral. The resistance I felt when the bike was in gear was that of the u-joint grinding into the housing.. not the engine turning under compression.

    So, the diagnosis was: Stuck engine (which we (my brother and myself)) should be able to free, and a transmission/rear end that needs a going-over/rebuild (the transmission, I will probably take to a shop). This is what you'd expect from a barn find.

    (What the outside of the transmission case was telling me: Someone rode it for a (hopefuly short) time with the u-joint being so loose. I believe there's little to no chance that just trying to popstart it would have caused all the grinding/flakes, the break/crack, and the nut to back off so far. Thus, I believe this bike came to a rest (for 2 decades) seconds before disaster.. when the driveshaft (with u-joint and flange) actually could have disconnected during a ride and destroyed everything.)

  6. #6
    I removed what I could of the exhaust (thank God I had that exhaust nut wrench handy).
    I took off valve covers.
    I removed rocker arms/push rods.
    I removed both heads.
    I removed 1 cylinder.

    Bad news:
    1) I had to remove the front upper cylinder stud on the right side. There was plenty of "wiggle room" but when I would pull the head out to the threads, it would get stuck on that 1 stud. WTF?
    2) I was able to scoot the exhaust on this right side almost out of the head, but it's not coming out. I've tried tapping, pulling, turning, etc. So, I have a head sitting here with a part of the exhaust still attached. WTF?

    Good news:
    1) Right hand cylinder bore looks very good. Some crap (carbon?) was sitting in it, but there is no real rust or anything.
    2) Left hand cylinder (the stuck one)... something must have made a little nest inside. There is all kinds of crap (looks like a big pile of salt & pepper)... but, most of the surface rust can be rubbed away just by touching it. The bore feels pretty damn good as well. I think it could be freed relatively easy. The cylinder wanted to be pulled off, it was just stuck to the piston. I sprayed more stuff around the piston.
    Pics of the project at that state:

    The corner of the dungeon:

    Disassembling heads:

    The bore of the left cylinder:

    Crankshaft spins, though:

    The series of confusing events:

    Had to remove that stud to get the head off (WTF):

    ...and the exhaust just wouldnt come off.

    ..all kinds of purple dust came out of the exhaust. I thought I got a picture of it, too, but I can't find it.

    I put the left head back on, and filled up the cylinder with various things. I let the stuck piston soak.. for a long time (and it freed up some of the junk in/on the head/cylinder). I wanted to make sure I did as little damage as possible when I eventually freed it. Also, I fabricated some universal tools for the job.

  7. #7
    Piston is free and looks pretty good (cleanable/useable), besides the stuck rings. Cylinder looks better than expected.. haven't even tried to get the exhaust off/out.

    The wrench was not in the original design of the tool I put together, but I needed a tad bit more torque..

    The stuck piston says "89,975"

    I can only assume those circles are from an earlier attempt of mine to free the piston.

  8. #8
    Well, school was getting in the way more and more, along with a couple other projects, and just trying to keep my other bikes running.

    But, I took my heads to the "local" airhead shop to get "reconditioned," since that guy knows what he's doing.
    Time passed..

    Got the heads back. Got new Black Diamond valves, seats, guides, springs, etc.

    I was still, slowly cleaning the pistons.

    I was hunting down the holy connecting rod tool... Advance Auto didn't have one because "we're a car store," Ace Hardware didn't have any, but I found an 8mm at Napa. I thought it was the wrong size, and I found out it was. So, I was searching on advrider, and found post #51 in "Airhead Tips & Tricks". I went and picked that ("OEM Industrial" set, part # 25015) up on 11-27-07 for $12.99 like he said. A HELL of a deal compared to the other places I looked.

    I finally had some free time to work on the bike. So, I did a little research and dug right in. I went to take off the first connecting rod bolt, and "KKKKKKKK" and the ratchet almost flies out of my hand. MOTHERFU...

    The POS tool killed itself:

    Thankfully damage to the teeth on the inside of the bolt is minimal.. but there's now an infinite amount of metal flakes everywhere.

    I sat there, staring at it, pissed off, for an hour.


    A day later, I took it back to Autozone.
    “I’d like to return this tool that broke.” - me
    “Ok, [balhblahblah]. Here’s your mon--- wait a minute, this things broke!” – worker 1
    “Oh, just give him his money.” – worker2
    Last edited by crazydrummerdude; 10-02-2008 at 04:43 PM.

  9. #9
    On 09-12-08, after a few false starts, I finally was ready to button the engine back up.
    I called up Anton. He walked me through the process, to make sure I hadn't forgot anything in the mean time.

    I went to my shop and got to work.

    (Well, this post is worthless without pics. Unfortunately, after taking many detailed shots with my sweet new Canon EOS XTi Rebel, I got a "Card Error" message, and it didn't show any of my pics. Contrary to the threads title.)

    I've got to move to a town with a reliable airhead shop with the parts on hand, because this assembly required a lot of modification.
    -The pushrod tube seals were too loose on the pushrod tubes (My fault). (They will be monitored and replaced if they leak. (Very likely.))
    -The head gaskets dimensions were off (no, not at the pushrod holes) (not my fault).
    -Most annoyingly, the rings. The cylinders were measured to be straight and true with less than .002 over the diameter (according to the Clymer). After I got reamed over the rings online in terms of quantity and price, the end gap was significantly larger than expected. Larger than a +.002 diameter would cause. The end gap isn't incredibly awful, just on the outside of the recommendation. So, they'll do.

    Apart from that, everything measured up pretty good.

    Cliff-notes: So, the engine is back together. After 9 months of it sitting in parts in the corner of my shop, that is a gooooood sight.

    The transmission is the only thing keeping me from taking it for a spin around my field. My plan for that is to find a replacement rear panel and have it rebuilt. This should happen before it gets too cold.

    Unfortunately for the project, I now live 110 miles from it. So, (efficient) work will be done roughly every other weekend until I get a house here and can bring it down with me.

    We are now up to speed.

    I'm currently accepting donations paypal to

  10. #10
    BeemerBoy terham's Avatar
    Join Date
    Feb 2005
    Exit 31, PA TPK
    Current rides R75/5 R100RS R1150RT
    Past rides K100RS R1100S
    My Smugmug

  11. #11
    --Tony AnnapolisAirhead's Avatar
    Join Date
    May 2007
    Watkinsville, Georgia/Annapolis, Maryland

    Thumbs up

    Great post! Looks like the 90/6 I bought with my R100T (including the find-the-airhead in the grarage pic...could've been my PO's garage). Sadly, stupidly I sold it, running but I needed the cash. Damn, I think I had the same seat! My Krausers were white, so I kept them...uh, why? Not sure but I did.

    One thing I learned after snapping a few bolts is that when tightening into aluminum without torque specs it defaults to the "snug-it-til ya fart rule" that a fellow airhead, um, enlightened me with one project or another. "Yeah, that oughtta about do her".

    Look forward to more...great project.
    1971 BMW R75/5 | 1975 Moto Guzzi 850T Cafe | 1983 BMW R100RS | 1988 BMW R100GS
    1988 BMW K75 | 1998 BWM R1100RT | 2000 Moto Guzzi Quota 1100ES |2002 Moto Guzzi V11 LeMans

  12. #12
    You got big balls taking on project like that. I love picture of your bike and stories, keep them coming. Someday I also would like to get project going like that, to learn a lot in the process and be pround of your new baby when done. Problem is, everything you touch, parts wise, is very expensive and sometimes hard to get. But maybe someday...

  13. #13
    --Tony AnnapolisAirhead's Avatar
    Join Date
    May 2007
    Watkinsville, Georgia/Annapolis, Maryland
    Quote Originally Posted by 04r1150 View Post
    Problem is, everything you touch, parts wise, is very expensive and sometimes hard to get. But maybe someday...
    What the hell else are ya gunna do with the money? Braces for the kids? Mortgage? New appliances? Jewelry? The take on a project like this at 75 or 80 years old? Rubbish...dive in head first. Haha

    I wish I'd not waited until I was gray haired.
    1971 BMW R75/5 | 1975 Moto Guzzi 850T Cafe | 1983 BMW R100RS | 1988 BMW R100GS
    1988 BMW K75 | 1998 BWM R1100RT | 2000 Moto Guzzi Quota 1100ES |2002 Moto Guzzi V11 LeMans

  14. #14

    Moral Support from the Deep South

    Comrade, we work for the good of the Fatherland and all that is good ......Katarina Witt.....and BEER!!!!

    Now I understand where you got the experience to help out on my R100T project. And I must say that your 90 may give the Renegade a run for your money.

    Hang in there and keep posting and I will do the same. Remember, it's not a race and nobody gets out alive.

  15. #15
    Great thread! Thanks for sharing. Will eagerly await next post and next set of pic's.

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