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Thread: Buying used 1991 K100RS with 50K miles: what to look out for?

  1. #1
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    Buying used 1991 K100RS with 50K miles: what to look out for?

    Hello, folks,

    I'm thinking about buying a 1991 K100RS 16-valve "flying brick" with about 50K miles on it. I'd appreciate any advice on mechanical issues, etc., that I should be looking out for.

    I'm not all that familiar with these models. My one and only bike was a 1971 R75/5 workhorse that I sold to my brother-in-law last year.

    Thanks.
    Last edited by larrytepper; 05-29-2013 at 03:55 PM.

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    The Flying Bricks are pretty tough bikes. Built well and they seem to run "forever". Only issue I had was final drive. Can't think of anything else "mechanical" at 50,000.

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    Quote Originally Posted by EMSimon View Post
    The Flying Bricks are pretty tough bikes. Built well and they seem to run "forever". Only issue I had was final drive. Can't think of anything else "mechanical" at 50,000.
    Thanks, Mike.

    Greater Cleveland? I grew up in Parma and Middleburg Heights, graduated from CWRU. I live in Boulder, Colorado now.

  4. #4
    still running...somewhere lostbearings's Avatar
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    Rear engine seal...

    The only issue is the rear engine seal. It can fail and leak slowly and be an annoyance. It can also fail and mess up your clutch cause a replacement of clutch. There is a drain hole in the housing between the engine and the transmission at the bottom. If there is oil there, you have a leak and the seal needs replacing. It is a big job but there is information on the internet and you can do it yourself if you take your time. It takes a mechanic about 4-5 hours labour to replace the $30 seal. Once it is done, you are good for another 10 or so years.

    I sold my 1988 K100RS and still miss it.

  5. #5
    Kbiker BCKRider's Avatar
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    larrytepper - I own one and like it a lot! (Great power - 100 hp, much more than earlier K100's; gas mileage always above 50 mpg; RS fairing is wonderful - protection but not too hot in the summer; little vibration - about like my previous K75; no "engine heat" issues for the rider. Fewer final drive issues (Paralever) than earlier K-bikes.)

    THINGS YOU DIDN'T MENTION: price, appearance, maintenance records, luggage, shocks, seat, tires - both tread and age, does the ABS work, battery age, and your mechanical ability. I would think $4000 - 5000 is fair IF ALL THE FOLLOWING APPLIES; looks great, all gauges and ABS work, records of maintenance - especially clutch spline, which should be done around every 40K and is NOT simple or cheap, luggage cases in good shape, an after-market rear shock (original usually toast in 25K miles,) an after-market seat (mine came with the original and it was pretty bad. Substituted a Corbin I had saved from my K75,) tires which aren't too old (more than 5 years) a battery which still works.

    In short, if the bike has been used recently, still runs, has been serviced with some regularity - probably worth a very close look. BTW, if it HASN'T been run for a year or more, don't start it! You (or a mechanic) will need to go through the bike very thoroughly, change all the fluids, etc. so you DON'T damage it. Price drops to $1000 - 1500 if it is clear the machine needs a lot of attention. This is where your mechanical aptitude comes in. If (with the help of a Clymers and Haynes manual, and a lot of advice on this forum) you figure you can fix any problems, these bikes are worth saving. We all need more information on the bike to give you better advice.

    COMMON FAILURES I've EXPERIENCED:
    1. ABS failure. Can be hard to diagnose and, sometimes, expensive to fix. Not uncommon on these bikes either. I've learned to live with no ABS for a couple years.
    2. The exhaust pipes to muffler connection is prone to failure; more so than on earlier K's I understand. I had a specialist welder fix the one broken connection, and so far it has held. Advice from others on this forum was not encouraging when I encountered the problem. Check to see if the bike you are looking at has an after-market muffler/exhaust system. The replacements were expensive but apparently solved the problem. My understanding is that they are not currently available new.

    Do get back to us.
    Doug
    1992 K100RS

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    Quote Originally Posted by larrytepper View Post
    Thanks, Mike.

    Greater Cleveland? I grew up in Parma and Middleburg Heights, graduated from CWRU. I live in Boulder, Colorado now.
    Small world, Larry! I live in North Royalton. Have you been back the last 20 years?

  7. #7
    Registered User argent brick's Avatar
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    You might want to also ask around on the motobrick.com website. They focus on the flying brick K bikes. Lots of good info.
    Lynn
    MOA #57883
    Current Ride: 1995 K75 Standard
    Past: 1978 Yamaha XS 750, 1976 BMW R60/6

  8. #8
    2-up and havin' fun sugarhillctd's Avatar
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    Larry,

    I have a '92 K100RS (had a '93 K1100RS but sold it for an '09 Kawi Concours in a moment of true stupidity)

    Listen to the advice about the bell housing "weep hole". My previous '93 developed a rapid leak and the clutch started slipping quickly. But I did the entire R&R over a 3 day period. It was easy.

    Yeah the ABS can give you occasional fits, but my current '92 has been faultless.

    BTW, it had 40K miles when I bought it. Zero problems.

    Overall, these bikes are really reliable and are very hard to kill. There are brick engines out there with a couple hundred thousand miles on them.

    Pretty soon Paul, Don &/or 98Lee will contribute here.

    Best of luck...let us know how this turns out.

    Another good source of K bike knowledge is http://k11og.org/forum/index.php

    John
    John & Cathy
    '92 K100RS (gone- '04 R1100S Boxer Cup)
    '12 Suzuki DRZ400
    ("kid's" bikes) '02 Kaw ZX6R- Jen's '07 Duc 800ss- Johnnie's

  9. #9
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    One thing to always do when considering any early K; Open the gas cap and remove the four screws that attach the cap assembly to the tank, and remove the cap assembly. Now you can inspect the inside of the tank.

    Look for ANY discoloration to what should be shiny bright aluminum. If you see any brownish tinge, it could be from a dissolving rubber pump damper. Try rubbing your finger on the rubber of the damper. It should be hard, like the consistency of a tire. If it's soft or gooey, it needs changing before any gets sucked into the fuel pump.(Very common on bikes that have sat a lot).

    Look along the inside lower seams, especially on the left side just behind the fuel pump. If that area is dull and corroded looking, that is a sign that water has been accumulating there and instead of rusting through, it is starting to corrode through. (Very common on bikes that have sat a lot). Bubbling paint on the outside in that area indicates leaks are either present or just weeks away.

    During your test ride, look for any unwillingness in down shifting (especially from higher gears). That could be a sign of dry or worn clutch splines.

    Look for any coolant or oil out of the front weep hole. ( Sign that the oil/water pump needs to be rebuilt).

    Look for any oil out of the bellhousing weep hole. (Sign that at the minimum, the O-ring on the flywheel nut or the rear main seal needs replacement).

    If you can, see if the fan spins freely, with little drag. Then let it idle for 10 min. To see if the fan comes on BEFORE the overheat light comes on.



    If you buy it, you want a baseline so you KNOW the maintenance condition of YOUR bike; you should go through all the fluids ( including coolant and brake), lube the barrel on the clutch cable, check the valve adjustment, check the brake pad thickness, check and probably replace the crank case vent hose, check the hose between the radiator cap and the overflow bottle for ANY cracks. Check the compression (with throttle wide open), put in the correct new spark plugs.

    Get a Clymers manual.

    Get a spiral wound binder and start a log book. Put the date and mileage and what you did ANYTIME you do ANYTHING to it. Write in the valve adjustment numbers when you first check it and the compression numbers. Part of the problem with these bikes is they run so long between a lot of the maintenance items, it's hard to remember when you did them last so it helps to have it all written down.


    Most important, RIDE! Rides lots! Ride far! Ride often! And try to keep the grin on your face from getting too big (your wife will start to wonder what your up to).


    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

  10. #10
    RS MotoBrick
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    greetings larrytepper...

    if it were me i would be looking for some ethyl and some twisty roads...

    j o

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    Quote Originally Posted by EMSimon View Post
    Small world, Larry! I live in North Royalton. Have you been back the last 20 years?
    Yeah, I was back home last December. I still have siblings and lots of cousins there, plus a lot of friends from high school and college I'm still close with, even in-laws who ended up there by total coincidence.

    When I moved to Colorado people were making fun of Cleveland because of the Cuyahoga River burning. Every time I'd respond with something unique and great about the area, things like the Metro Park system, how we had actual ethnic food, rye bread cooked in neighborhood bakeries. Before long they were calling it the Center of the Universe.

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    Quote Originally Posted by larrytepper View Post
    people were making fun of Cleveland because of the Cuyahoga River burning. .
    Only those who didn't have the facts....

    Reason I asked whether you had been back, I am living there for 22 years now and in that time, the southern suburbs have changed so much, I can hardly believe it.
    Parmatown Mall is basically dead, the area south of there, right along Ridge Road has been developped with a Target, an Outback and several other places added, and the rush hour traffic on Ridge in both directions has become a nightmare.

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