BMW   K100RS

MotoCo Ducktail 



Another amazing K bike !   October 1987 K100 RS with MotoCo Ducktail has a recorded mileage of under 4,000kms. It is still wearing its original PIRELLI PHANTOMS, with muchos tread remaining.   It would have to be one of the least used K bikes now in existence.


I probably have the copy of the registration certificate somewhere for this bike, they will sometimes verify recorded mileage.. otherwise verifying mileage is a very subjective matter. The age cracked tyres are the original fitment PHANTOM +1's with next to no wear. The tyres are both date stamped 1987. All control operating surfaces are totally unworn, that is handlebar rubbers, gear selector rubber, foot peg rubbers and the diamonds on the rear brake pedal.. the usual wear points - zero wear. I have a graph of rear disc brake wear against mileage for K's very useful in getting a rough indication of mileage... the black K100 pictured at the bottom of the page had 85,000 kms on the clock and the disc was so thin you could almost shave with it. On the other hand this particular K100 has ZERO, no discernable wear at all.  

The MotoCo ducktail mono seat arrangement is a feature only found on a very few Japanese market K100's. I have had another K100RS in this configuration a number of years back but it is very rare to find one.I have only ever seen these two offered for sale over the years and I purchased both. The ducktail was a significant $1,500 extra cost item in 1987.

This combination results in a lower seat height... I am a tall person but I find this arrangement a lot better than the typical K series "plank".. not much use though if you want a pillion passenger. Behind the seat is a lockable rear compartment with plenty of storage room. This is also the location of the complete BMW tool roll for this bike. The ducktail simply unbolts and a standard dual seat can easily be fitted... it goes straight on.

Work very much the same as applied to my K75S  was carried out to this K100..  The fuel tank internals were replaced, that is fuel pump, anti vibration damper, intake filter, all fuel lines, internal submersible and external pressure lines to the regulator, and also the fuel level float and the sender unit. Pump was a genuine Bosch unit.

The forks and the triple clamp were removed so that the headstem bearings could be cleaned and regreased. All the injectors and the fuel rail were removed and cleaned, new o rings were fitted..  The original rear mirrors were knocked around during transport and I have replaced them with a brand new set.. I have left them in the undercoat white.   In summary nearly the whole fuel delivery system has been replaced.

  Engine oil and coolant were replaced. I haven't touched any mechanicals as there has been no requirement, in fact I have never ever had to touch any K bike mechanicals, apart from normal service and I've owned a lot of them.I did removed the plugs when it arrived and gave it a generous squirt of lubricant into the bores and turned it over by hand on the centre stand..


                                                   Tokyo Auctions 2010


I carried out this work over two years, ordering in parts when needed, mainly from the US but also the UK.  The fuel lever sender I found locally.  I had almost got it to the point of running but my fathers death in March this year brought work to a halt.  It is only recently that I have been able to complete the bike.  Recent work was focussed on the injectors and thoroughly cleaning the fuel rail and fuel line south of the pressure regulator. 

The bike rides is clearly the best  K100 I have ridden. The standout feature when riding is the total lack of driveline slop and precise gear selection and very very quiet mechanicals.  After all the work it's hard to describe how much I enjoyed that first ride..though I didn't forget I was on 27 year old rubber.  

Above is the K100 getting a new delivery fuel line to the pressure regulator, yes this practically what you need to remove to get to the pressure regulator,,,cooling fan bearings get lubed at this stage while the radiator is out. These fan motors have plain brass bushes back and front that need a drop or two of oil every now and's not optional either as they will get tight and may burn out eventually without this occasional attention..

 Looks like the tank and fairing got a coat of paint sometime over the years ....

My earlier K100 Ducktail above,, this one had 85,000Kms on the clock and was fitted with spacers that brought the bars further back, plus it had optional factory auxillary fuel and temp gauges fitted from new... a lovely bike, it rode beautifully and is still in the hands of a friend.




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