1 Throttle Cable Repair and Custom Manufacture Fri Apr 05, 2019 8:59 pm
redrockmania
Silver member
I am in the final stages of an upgrade to the front braking system of my 1983 K100. The system is a little hybrid but I think it will be a big improvement on original. I purchased 2 new Brembo Gold P4 30/34 callipers and machined an aluminium billet adaptor plate to fit onto the original fork legs. I found what others had discovered, the standard front brake master cylinder (12 or 13mm) has too small diameter to exert the necessary pressure and after looking at the complexities of fitting a non-BMW larger diameter master cylinder abandoned that idea in favour of fitting a K1100 or R1100R 20mm diameter Magura M/C. These take the K100 right side switch gear. If you use non-BMW switchgear you are in for a major rewiring job.
The 20mm master cylinder housing has a different throttle cable mechanism. The earlier K100 throttle cable will not work with it. I purchased used K1100RS and RT throttle cables but the longer of the 2 cables was still too short. I botched shortening the outer black plastic/steel cover on the cable, cutting several strands of cable wire while "carefully" using a Dremel-type tool. What to do? The key parts required to home make a suitable replacement cable are the plastic end mouldings on the K1100 cable - the top bent plastic moulding that locks into the throttle/front brake master cylinder mechanism and the bottom plastic flange/tip that fits into the cable bracket on the throttle body. On my metal lathe I machined from brass a copy of the plastic flange and at the thickest outer part drilled and taped a M3 thread through to the internal hole the cable fits into. I fitted a M3 grub screw and after tightening have a strong and secure bottom cable flange. The flange will not come loose, and, because it can easily be removed, then refitted, it is possible to easily adjust throttle cable length, or, build a new cable. I looked online at throttle cable repair/making kits and was horrified at their price (I'm also horrified at the price of new cables and listed second hand cables). I had an as new Renault tailgate cable on hand. It was long enough to make a replacement cable - the wire was of suitable size and the cable outer has a plastic liner allowing the steel cable to move smoothly without lubrication. After machining up two cable end BRASS nipples to K1100 size I soldered them on and have refitted my new custom cable - works perfectly.
I did an online search for "motorcycle throttle cable kits" and "Motorcycle Bowden cables" and was horrified at the prices being asked. I've found an alternative source for affordable suitable stainless steel cable. Bicycle gear change cable is correct specification and available at a fraction of the cost. Hope this helps and inspires - not for everyone.
The 20mm master cylinder housing has a different throttle cable mechanism. The earlier K100 throttle cable will not work with it. I purchased used K1100RS and RT throttle cables but the longer of the 2 cables was still too short. I botched shortening the outer black plastic/steel cover on the cable, cutting several strands of cable wire while "carefully" using a Dremel-type tool. What to do? The key parts required to home make a suitable replacement cable are the plastic end mouldings on the K1100 cable - the top bent plastic moulding that locks into the throttle/front brake master cylinder mechanism and the bottom plastic flange/tip that fits into the cable bracket on the throttle body. On my metal lathe I machined from brass a copy of the plastic flange and at the thickest outer part drilled and taped a M3 thread through to the internal hole the cable fits into. I fitted a M3 grub screw and after tightening have a strong and secure bottom cable flange. The flange will not come loose, and, because it can easily be removed, then refitted, it is possible to easily adjust throttle cable length, or, build a new cable. I looked online at throttle cable repair/making kits and was horrified at their price (I'm also horrified at the price of new cables and listed second hand cables). I had an as new Renault tailgate cable on hand. It was long enough to make a replacement cable - the wire was of suitable size and the cable outer has a plastic liner allowing the steel cable to move smoothly without lubrication. After machining up two cable end BRASS nipples to K1100 size I soldered them on and have refitted my new custom cable - works perfectly.
I did an online search for "motorcycle throttle cable kits" and "Motorcycle Bowden cables" and was horrified at the prices being asked. I've found an alternative source for affordable suitable stainless steel cable. Bicycle gear change cable is correct specification and available at a fraction of the cost. Hope this helps and inspires - not for everyone.