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Thread: Buying a K75S on Saturday

  1. #1
    Registered User detbmw's Avatar
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    Buying a K75S on Saturday

    I'm am buying an '87 K75S with 55K miles on it this Saturday.

    Curious as to what engine & transmission/FD oil I should use?

    What tires I should buy?

    What air pressure I should run?

    Let the cage match begin!
    Rich
    Night Black 2000 R1100RT
    Marakesh Red 1988 K75S "The S is, by far, the finest-handling BMW we have ever ridden." Motorcyclist, November 1986

  2. #2
    Registered User kgadley01's Avatar
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    Mobil 1 20-50 Syn in the engine and Mobil 1 75-90 syn in the tranny and the rearend.
    AKA SNAPGADGET
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  3. #3
    Themason 42906's Avatar
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    Since the bike has a dry clutch and separate gearbox lube, you don't need an engine oil rated MA1 for wet clutches. Mobil-1 15W50 car oil is fine, cost less than the 20W50 motorcycle oil and is readily available in nearly any auto parts store.

    I use Mobil-1 75W140 gear lube, but I live in the Mojave Desert out near Death Valley where it's screaming hot in the summer and below freezing in the winter. I need the heavier rating when fully hot.

    Tire arguments start to get personal. I actuall did a paralever conversion on an old '84 K-100RS so I could access modern high performance radial tires. The K-75 wheels are too narrow for most rear radial tires out there any more, though there are lots of good 110/80ZR18 fronts to choose from. I was running a 140/80ZR17 Avon on the rear before changing to the wider wheels of the Paralever bikes.

    The Avon rear is the Azaro AV-46 ST 140/80ZR17. The Avon front tire is the Storm 2 Ultra Front 110/80ZR18. These are as good as you are going to find for your wheels. They are actually very good tires, nice and neutral and great on wet pavement. They are quite a bit more durable than bias ply tires so cost per mile is more than competitive. I just don't know how much longer Avon will make that Azaro rear. It's been around for quite a few years, and there is no matching size in the more recent Storm series tires. No one else makes a 140/80-17 radial rear tire any more. I remember pleading with the Dunlop rep not to discontinue the D205 in the sizes I used, to no avail. That is when I switched to Avons, but that deal cannot go on forever. Enjoy them while you can is all I can say. When that rear disappears you will be stuck with bias ply garbage, or you can convert the K-75 to Paralever, of which I have seen and ridden several.

    Btw, a 120/70ZR18 front will fit your wheel and not rub the forks. I found this out when a tire shop mounted that size by mistake. It steered a bit differently than I was used to, which is why I looked at the size. The shop agreed to take it off and give me the size I wanted, but that size is an option if you like how it steers. It will fit.

    I run 42 psi front and rear on radials, and that is as much about steering feel as it is to protect the wheels from damage on LAs worn out freeways.
    Experience is what you get when you don't get what you want.

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    Quote Originally Posted by kgadley01 View Post
    Mobil 1 20-50 Syn in the engine and Mobil 1 75-90 syn in the tranny and the rearend.
    Ditto


    Bridgestone BT45 V rated.

    Start with 36F - 36R. Adjust to your weight / riding style. They work better with lower rear pressure than other tires. The slightly higher than factory front pressure helps with initial turn-in, making the bike extremely clickable in the twisters.


    If the shock is original, it's probably worn out. Replacing the front springs with Progressive front springs with factory spec oil weight and amount and a new Progressive 412 shock will yield a VERY good handling bike. You can spend WAY more to get slightly better, your choice.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
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  5. #5
    Themason 42906's Avatar
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    I have a Progressive shock I ran on my K that is trash. The shock body itself wore out around the mounting eyes. There was vertical travel in the shock I noticed while washing the bike. I bought new spherical bearings from Progressive and installed them, but the holes they fit in were hogged out. This is the problem with using heim joints or spherical bearings to mount shocks on a street bike. The shock is not repairable and thus worthless.

    Works Performance can sell you a shock with urethane mounting eyes that will last a good deal longer that those miserable spherical bearings and do not damage the shock body when they wear. This is what you want on a street ridden bike. Price wise they are more than competitive with Progressive, made in Los Angeles, and a better quality piece. Works does not sell an off the shelf shock. All are custome made to your weight and riding style. Rebuilds are around $67 plus shipping and any parts that are found damaged or worn out. In general their service prices are extremely reasonable, and you talk to the tech working on your shock.

    Front springs can be had from Works Performance, Wilburs or Race Tech in addition to Progressive. If you buy springs from Works Performance you can have both ends tailored to your weight with spring rates that are compatible front and rear. Ditto Wilburs if you buy one of their shock, keeping in mind that Wilburs uses heim joint eyes that could be damaged by years of hard street use.

    I wouldn't spend the money on a Cartridge Emulator on that fork. Your bike has the good fork, from Fichtel Sachs. Use 7 or 7 1/2 wt fork oil and enjoy it. For such an old fashioned damper rod fork it works darn well.
    Experience is what you get when you don't get what you want.

  6. #6
    Mars needs women! 35634's Avatar
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    That could be one of the original litter, http://www.bmwmoa.org/forum/showthre...ghlight=litter


    Check if the serial # is between 150001 and 1500325

    I don't think these engines are too particular about oil, spend what makes you happy and is appropriate. I noticed a little easier shifting when I switched to synthetic gear oil.

    Bridgestone Spitfires are good economic tires, BT-45's are better.
    1987 K75S
    Original litter
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    2012 Ural Gear Up

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    Quote Originally Posted by 42906 View Post
    I have a Progressive shock I ran on my K that is trash. The shock body itself wore out around the mounting eyes. There was vertical travel in the shock I noticed while washing the bike. I bought new spherical bearings from Progressive and installed them, but the holes they fit in were hogged out. This is the problem with using heim joints or spherical bearings to mount shocks on a street bike.
    You are talking about the higher priced Progressive 465 shock ($495). The rubber bushed 412 lists for $299 but can be found for around $225. Front Progressive springs can be found for around $70. The combination is very well balanced (front to rear balance is more important than all out control at just one end).

    Works rear shock is $539. They don't list a front spring for a K75S. The springs for Cs and RTs go for $149. I've ridden several Ss with Works suspension and did not prefer the handling over the Progressive 412/Progressive front spring setup.

    Wilbers, YSS, Ohlins, etc. will cost multiples of that. The improvement to handling may be noticeable, might not. The cost vs the price you paid for your bike will be noticeable.

    This is a new bike to you. You might want to see how it suits you for a year or two before you start throwing BIG bucks at it. For $500, you could have new tires AND suspension that I KNOW will be a good handling combination to start with. Down the road, if you want to "personalize" it with high dollar parts at least you will have a solid place to be starting from.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

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    Quote Originally Posted by 42906 View Post

    I run 42 psi front and rear on radials, and that is as much about steering feel as it is to protect the wheels from damage on LAs worn out freeways.

    Detbmw,

    That high of a pressure is only necessary on the flexible side wall radials (radials are NOT recommended for the stock rims on your K75S) . High pressures are not needed to protect your Y-spoke wheels from damage. Only the later 3 spoke rims have bending issues (which is what 42906 has).

    You don't have a paralever (but you could install a new tranny, driveshaft, paralever swing arm and final drive and a few other parts like 42906 did). The recommendations don't apply to the bike YOU are buying.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  9. #9
    Old man in the mountains osbornk's Avatar
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    If you decide to use synthetic lubricants, keep an eye out to leaks and seepages. I tried it on two older BMW that were both newer and had less miles than the one you are buying and they both had seepage problems. The 85 K100 leaked at the rear seal and the R80 seeped at the push rod tube seals. When the seals get old, they harden and are more apt to leak. Both of them quit leaking when I returned to a conventional 20W50 Castrol. I had no problems with a newer oilhead and with newer cars.
    'You can say what you want about the South, but I almost never hear of anyone wanting to retire to the North.

  10. #10
    Themason 42906's Avatar
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    Quote Originally Posted by 98lee View Post
    Detbmw,

    That high of a pressure is only necessary on the flexible side wall radials (radials are NOT recommended for the stock rims on your K75S) . High pressures are not needed to protect your Y-spoke wheels from damage. Only the later 3 spoke rims have bending issues (which is what 42906 has).

    You don't have a paralever (but you could install a new tranny, driveshaft, paralever swing arm and final drive and a few other parts like 42906 did). The recommendations don't apply to the bike YOU are buying.



    1988 K-100RSs came with Dunlop radials stock. There used to be a number of good radial tires that fit the stock narrow rims and I have probably used every one of them over the years.

    At various times the original rims saw radials from Michelin, Avon (AM22/AV23, great tire combo), Dunlop (D205s for about ten years) then a short stint on bias ply Michelin Macadams when Dunlop ceased making D205s in sizes for those rims (tossed those particular Michelins before they were worn out) before going back to Avon radials.

    The stories people tell that you aren't supposed to run radials on those rims? Uninformed nonsense. I did for over 15 years before the Paralever conversion. Most of these tires returned in excess of 10K miles front and rear and that was on a heavier bike with more power, better than any bias ply tire ever did. Dollar per mile radials are superior, and they handle better too boot.

    The Michelin Macadams were actually scary tires, they would slide before I even touched a peg in a corner. One of the worst tires I have ever used, and I usually love Michelins (I run Pilot Road IIIs on the bike now as well as on the Street Rod). I had some hairy slides on the Macadams. The Dunlops and Avon radials stuck well enough to scrape pegs and stands without the bike doing anything scary. Both give better steering feel than a bias ply tire, and ride a bit better.

    Btw, I have bent both the three spoke rims and the original K bike Y spoke rims on LA chuck holes. The one that got the Y spoke rim was a piece of missing pavement in the fast lane of I-5 at one of these funky old interchanges where the exit to another freeway was from the left lane. Caltrans used to think that aided traffic flow. I hit the hole at about 70, knocked my hands right off the grips, but I kept it up. I found the dent later when I got to work and inspected the rim. I didn't use to run such high pressures until the techs at Martys BMW wagged a finger at me over that wheel and told me to run 42 psi in LA to protect the wheels. I have bent the suspension of my car on LA freeway chuckholes too. LA is tough!
    Experience is what you get when you don't get what you want.

  11. #11
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    My point is: your recommendations don't apply to Detbmw's bike.

    His is a K75S. Yours is a K100RS.

    His is monolever. Yours is Paralever.

    His bike specifies bias-ply. You have had lots of experience trying to find a radial that works on your bike. Some good some not so much.

    His primary concern is not the chuckholes of LA. One of your primary concerns is.


    He asked for recommendations on what would work well on HIS bike (a 1987 K75S). I have 4 K75Ss (1 '87 and 3 '88s) and have been doing work on primarily K75Ss, getting them sorted for their owners. The combination I suggested WILL yield a solid place to start from at minimal cost. The more "other" combinations I ride, the more I like this one.

    To suggest that he START by experimenting with non-recommended radials or high dollar suspension before he even learns the strengths or weaknesses of the bike and the way it's supposed to handle may be premature. When the K75S came out, the motoring press hailed it as the best handling BMW to date. Better than the K100s, better than the airheads, way better than the K75C.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  12. #12
    Tom Mieczkowski mieczkow's Avatar
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    I have the setup on my '87 K75S as described by Lee (Progressive 412 rear shock/Progressive front springs). Excellent combination for the money and it has given me years of good service.
    Tom Mieczkowski
    1987 K75S

  13. #13
    BMW uber alles! Zagando's Avatar
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    +1 more recommendation on the Bridgestone BT-45s from my actual experience as well.

    I respect both 42906's and 98Lee's advice however what Lee said above is 100% on target, IMO---and his recommendations really pertain that the bike you are getting tomorrow (most important!)

    Congratulations and a big Yippeee! to you on your new K75S, Hope you are totally stoked!
    ---Jeff '94 K75S Berlina

    ex: R100GS/PD , K100RS , R75/5 , R60/2

  14. #14
    Registered User detbmw's Avatar
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    Thanks for all the advice. I've been working and today driving up into Oklahoma to get the bike so I haven't had time to digest everything that ya'll have posted.

    I meet the owner, who is trailering the bike 150 miles to get here, in about 14 hours (11 a.m. Central on Saturday); I can't freaking wait! I saw several up close at Sedalia this summer, but I've never ridden or even sat on one. But the more I read about the K75S, the more I want one of my very own.

    I'll have a six-hour ride back down into Texas tomorrow afternoon. I plan to check/lube the drive splines in the next couple of days, then change all the oils this next week. The bike has only been ridden 600 miles in the last two years, so I figure a full service is in order.
    Rich
    Night Black 2000 R1100RT
    Marakesh Red 1988 K75S "The S is, by far, the finest-handling BMW we have ever ridden." Motorcyclist, November 1986

  15. #15
    What, me worry? GILLY's Avatar
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    The best tire combo I came up with was the Metzeler Lazertech up front and Metzeler Marathon in back, both bias ply, stock sizing.
    87 K75S, bought new, now sold
    07 K1200GT Bought new, now traded in
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