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Recon for BMW K100 motor

Discussion in 'Bling and Appearance' started by temcee, Dec 14, 2007.

  1. Hi everyone,
    I am wondering if anyone knows if there is a kit available to recondition a motor in an old BMW K100?

  2. Try these guys.


    No "kits" that I'm aware of, but if your bike's done less than about 500,000 kms, I'd be surprised if it needs more than a camchain and new rings.

    What makes you think it needs a recon?
  3. Just to follow on....

    If a K100 lump does need more than camchain, rings, bearing shells and maybe an oil/water pump and a set of exhaust valves, I'd suggest that rebuilding is probably not your best option economically.

    Anything more than that can easily get you into the price territory where you could buy a complete bike with a good motor and have all the other bits as a bonus.

    A need for more could also indicate a badly abused or neglected machine. Much as I love the 2-valve K (and all other BMs for that matter), a dying one could very easily turn into a money pit.
  4. re k100

    thanks for your reply, this old girl has done just over 200,000 ks, has anoisy bearing (?) in the bottom end. A mechanic friend of mine said rather than only replacing this and associated bits , he would rather renew all bearings, seals etc so that I get lots more troubl free ks. My mechanical knowledge is limited -a female thing- but I am learning. I would only be paying for parts.
  5. Fair enough.

    I would be mildly concerned regarding a noisy bottom end on a K. There is at least one fault which can develop (allegedly) in the region that cam be hideously expensive (allegedly) to repair. Can't say for sure as mine hasn't done it in 250,000 kms so I've no direct experience, but output shaft problems are spoken of with fear and trepidation on internet BMW fora.

    While your mechanic friend has the bike apart, make sure he/she pulls the final drive unit off the end of the swingarm and slaps plenty of moly grease on the drive-shaft splines. Neglect of this little chore (doesn't take long) has cost more K100 owners more money than any other single cause.

    Oh yes, and then make sure he torques up the rear wheel retaining bolts exactly as specified in the manual. Failure to do so can result in the rear wheel attempting to depart at speed. Ahh, memories :grin: .

    Cracking bikes, but elderly ones do require a little familiarity.
  6. I'd honestly look at NOT rebuilding at this stage. No K100 is worth more than about $4500, especially not with a high miler. You could easily tear up $2000 with absolutely no return unless you plan to keep this bike for life. Pranged ones are cheap and while the valve and/or bottom end covers will be rooted yours will be fine. At the moment I know of a smashed K100 with about 90,000km on it. The owner was offered about $200 for the whole thing, but if you made an offer above $500 he might be encouraged to move it.

    There are a few things that do become noisy with age as PatB mentioned.

    One source of noise is the rivets that locate the shock absorber on the output shaft. In early bikes 6 rivets were used, and they eventually flog out. This causes a bit of a rumble that annoyingly takes an awfully long time to escalate to the point that the becomes a rather large garage ornament. In later bikes they used 12 that lasted longer.

    One of the wreckers I use, Discount Motorcycle Wreckers in Coburg, tell me that they have NEVER sold a K100 engine because they are generally the last thing to stop. Bikes become unviable to maintain because final drives, gearboxes, clutches and output shaft splines pack it in through lack of maintenance or mileage. However the biggest cause for decommissioning a K100 will be accident damage - especially the faired ones.

    Not to discredit your mechanic mate, but unless he's intimately familiar with the K Whiner motors, I'd take it to one of the specialist BMW workshops for them to assess if you really think it's noisy.

    Mine sounds very rumbly and knocky when cold, but once it's warm it runs like a sewing machine. It sounds odd, but espcially at idle, lack of proper synchronisation of the throttle bodies can exacerbate any mechanical noise. I recently sych'd mine with a home made manometer having done the valve shims and it made it SO much smoother.