#4 - R90S Powered /2 Conversion Period Hot-Rod

Discussion in 'Airheads' started by Solo Lobo, Jun 17, 2020.

  1. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    Lacking any inspiration for a witty title, this is simply going to be called #4

    This follows my previous project threads following my R80G/S, R65LS and R100RS, and this one very much follows in the same vein as the LS and RS.

    To start, I'll quote both the LS and RS threads:

    My list the qualities that would identify the perfect project bike include:
    #1 BMW Airhead
    #2 One of my list of 5 models; R90S, R69s (any /2 really), R100S, R65LS and a non-airhead a K1
    #3 Local bike
    #4 Known History (1 owner?)
    #5 Stored for some time (longer the better) and needing to be put back on the road

    This next project hits one, combines two bikes from 2, misses out on 3, I am working on 4 and hit 5.

    Backstory -

    The G/S was as finished as I was going to make it, then I found the LS which had the Luftmeister catalog thrown at it.... got that as done as I am going to make it, then found the RS which had even more of the Lufty catalog used on it. The RS is in it's final stages now (at least I hope so), and will be getting sold (as much as I love it) as I just can't use three bikes that do something similar and my wife really prefers the R65LS.

    Knowing the G/S was getting sold, I put up a general wanted add on the /2 conversion Facebook page, and was pinged by an inmate here who I have been chatting with for years. He said he had a 1966 R60/2 with a 1975 R90S engine that had reportedly been assembled in Austin TX years ago. He had another /2 conversion, didn't need this one and a deal was struck.

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    The R90S engine had a number of period hot rod things done: Briel sump extender, welded intake stubs, lightened flywheel, dual plug heads, intake porting, etc.

    Here are some of the first pictures I received:

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    So, last week I rented a van and tackled the 2,100 mile round trip

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    Played hooky on Monday and put the bike back together to see what I was missing. This is step #1 of the dry build

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    Some things I discovered along the way:

    Luftmeister "high performance" clutch friction disc... well used I would say

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    Holes for a blanking plate I am assuming

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    Some of that period hot rodding

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    Given the wear here, I am guessing that there wasn't as much engagement here as would really be ideal... I have the recent Vintage BMW Mag on conversions that details options to address this

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    More hot rodding

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    What's next? Well I am ordering parts from lots of different sources and will have quite a few boxes coming in shortly.

    Next, I am sure is more parts orders.

    My plan is to do a 100% dry build, including wiring and plumbing, then have any fabrication and repair done, tear down and paint (already have two possible colors picked out, and the options are not red nor black).

    Following the dry build and fab, while the paint is being done I'll tackle the engine and wheels - more correction I will have the wheels addressed. I need the change away from the 19" front and want to use matching alloy high shouldered rims on both ends.

    I will probably insert getting the motor running in there before paint in truth.

    For now the plan is to maintain the character and history of the bike, with the exception of new paint. I will be keeping the ATE calipers and (gasp) the under tank master cylinder as well (double-gasp).

    The engine and drive line will be cleaned and refreshed as needed (I have a Matt Parkhouse freshly rebuilt trans on the way now) and I will run the /2 final drive and swing arm for now as well.

    There is also a decent sized list of used /2 parts I will need, so if you have a stash please reach out to me and let me know.

    This bike really spoke to me. I am really happy to own it and am looking forward to this journey.

    *Update*

    A bit more on this bike's history - I purchased the bike from CA, the CA owner got it from a friend who had it in the NE, and that owner had purchased if from a guitarist in Nashville. The owner trail dies there as the guitarist didn't want to share the earlier owner's name.

    I also tracked down the builder of the bike who had an independent shop in Austin up until 2000. He built the bike, then bought it back (after the Plumber had an accident on it I believe) and then "rode it around Austin for years". He sold the bike in 2000 when he closed the ship, and it toured the country from there but the title never got out of his name, so I believe it toured as a project and not a runner.

    The builder said the bike came together in the early 1980's for a customer who was a plumber. The builder had purchased a large lot of R90S parts from another local racer (the builder raced an R100RS, and also won a race at Daytona on a Japanese 2-stroke of some kind). In amongst all the R90S stuff was Reg Pridmore's Daytona winning R90S, which he put back together and only recently sold it to Udo Gietl.

    The bike had the script "The Plumber's Bike" on the tank, and was at the 1984 BMW MOA rally in Missoula, MT and several members here remember the bike.

    The tank was loaned our by the Nashville owner and lost, but he still has the fairing. As much as I would like to have (not mount) the fairing, the cost of shipping isn't good. I'd also like to have that original fiberglass tank. IIRC, the tank was for sale on Craigslist years ago and I think I traded emails with the seller and only passed because it was fiberglass.
    #1
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  2. cwroady

    cwroady Broken Arrow Moto

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    Looks fun, I am looking forward to watching your progress. I am deep into a '55 R50 refurbishment myself currently. Bike components out for work (those beyond my confidence/competence level) from CA to PA, and other parts coming in from Mississippi, Germany and The Netherlands. Good time to have a significant project to work/play with! Enjoy and thanks for taking us along.
    #2
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  3. Kiwiabbo

    Kiwiabbo Long timer

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    Definatly looks like a fun project, relatively complete ish.
    #3
  4. tennessee thumper

    tennessee thumper Long timer Supporter

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    Sure you'll have some challenges but that's why you do these. Problem solving then reaping the rewards of your work.

    Enjoy!
    #4
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  5. 2WheelTraveler

    2WheelTraveler backinthesaddleagain Supporter

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    :lurk
    #5
  6. bmwrench

    bmwrench Long timer Supporter

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    That Luftmeister clutch probably escaped the update of hardening the pressure plate and ring. Before this was done, a number of sintered bronze plate (and the other plate) were destroyed.
    #6
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  7. sprouty115

    sprouty115 Long timer Supporter

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    :lurk
    #7
  8. tennessee thumper

    tennessee thumper Long timer Supporter

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    SL,

    You probably know this but with your 90S engine, check the VIN and note year/month of production when ordering parts.

    I've got the Ian Fallon R90S book. And while it may not be all end all on all that, it is helpful. Happy to verify, from there for you, if needed.

    Throttle cables, neutral switch, flywheel bolts, engine casting, master cylinder o rings, caliper pistons (yours look like 40mm with the grey color) are just a few of the things that changed over the production span that I had to catch up on quickly when ordering.

    As a first time 90S owner, I missed a few things on mine this past winter, even though I knew to verify parts specific to my VIN and date of build.
    #8
  9. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    I've accumulated some /2 parts in the last few months in prep for this project... unfortunately I also sold a few (that I could use now, LOL) when I was rebuilding the RS to years ago.

    Already on the shelf - rear solo seat (rack mounted), rear luggage rack, headlamp bash bar, new Hella bar-end turn signals, etc.

    Here is something cool - this is a 1977 5-speed transmission that Matt Parkhouse rebuilt as part of a 3-part series in the BMW MOA news letter back in 2005 in his "Keep 'em Flying" column, and hasn't installed on a bike yet. The transmission has the Ed Korn repair to the output shaft and 5th gear, a new input shaft, K-bike roller, bearings and seals...

    The transmission that came with the bike (5-speed as well) shift smoothly, had no metal on the drain plug, the oil was clean and looks to have been rebuilt before... but I budgeted for a rebuild and this trans became available. I may sell this the trans that came with the bike.

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    #9
  10. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    I learned from the PPO, that the PPPO was going to move from Dellorto's to Mikuni's. Wonder why?

    Never worked on Dell's before, but since I have the carb kits, and am still waiting on lots and lots of parts, why not jump into some cleaning?

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    The accelerator pumps are rock hard, the idle speed screw was all the way in...

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    I'll pull out the old "can o death" (Berryman chem dip) and see how these turn out.
    #10
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  11. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    I am still waiting on lots of parts to be able to tackle the dry build, and to identify any fab work needed.

    Impatience got the best of me and I decided to take a quick peak in to the cylinders using my borescope

    This is the left side, I tried the 45 degree angle attachment for the scope and the light wash made it really hard to get a decent shot

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    Clearly I picked the left side to start with and I was pretty hopefull... then I checked the right side... the engine did turn freely and smoothly

    Not too bad here

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    then I looked at the bottom of the cylinder

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    I'd say the exhaust valve was hanging open and water was introduced.

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    That meant I needed to pull the head and have a closer look, so I did

    Looks like a trip to the machine shop may be in order. I may hit it with my ball hone for fun, but am really think not to in this case

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    Here's the next point of interest... valve contact with the piston crown

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    Still working on cleaning the valves, but I don't see any witness marks on the valves... may need to pull them out to check thoroughly

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    I am not an R90S expert, but these pistons are unmarked, and look like high-comp replacements... very much like Oshmo sells

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    But no arrow on mine, here are Oshmo's which are 9.5:1

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    I don't think I want to run high-comp pistons on this set-up.

    Plan from here - get the cylinders to the machine shop to figure out of they need to be bored beyond the rust (have to think they will require is) and then figure out pistons from there.


    *update* just spoke to Autosport Seattle, and I am going to take both cylinders and pistons down to them next week to check out.
    #11
  12. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    So, not Oshmo, but Venolia

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    Same issue with the left side valve pocket

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    Garbage lifters

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    Garbage to the right

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    Doubled up valve springs

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    Rods were marked, and appear to be slightly polished

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    The big ends don't look so bad

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    Left

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    Left crank

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    Right
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    Interesting mark on the right ord

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    #12
  13. sprouty115

    sprouty115 Long timer Supporter

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    Ouch!
    #13
  14. eight90eight

    eight90eight Been here awhile

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    I saw yer bike in 1984 at BMWMOA rally in Missoula, MT. Got a picture if you want it, PM me with yer address. It had a zoomy fairing of some type, different seat, dels, etc. There’s some history alright. Had a big big Heinrich tank too. Good luck.

    The bike was sitting outside Bavarian Cycle Works barn/display. Good times.
    #14
  15. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    Thanks eight90eight, sending you a PM now!
    #15
  16. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    Just got the Cycleworks tool for the front shocks...

    Never seen this Koni logo before

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    #16
  17. bmwrench

    bmwrench Long timer Supporter

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    The interference between valve and piston is interesting. Does this piston set have the same valve relief for both intake and exhaust?
    #17
  18. Pokie

    Pokie Just plain Pokie.

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    Make sure that before you thread in the new shocks that you grease/ anti seize the threads in case you ever have to take them back apart. I've seen a lot of folks trash the old shocks just taking them apart.
    #18
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  19. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    [​IMG]

    the reliefs are not symmetrical, the larger one is ~2mm wider at the flat end

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    And the reliefs are vey different. I’ll add photos soon
    #19
  20. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    what is the trick to unthread the old damper? Strap wrench?

    anyone know of a rebuild kit for these old Koni’s?
    #20