I have a rather splendid K75RT in excellent condition but like its owner it is getting on in years. The fuel lines seem intact but they are pretty hard after aging for 18 years. I don't see any replacement interval in the Clymer or Haynes manual. How long are they really good for? Will they eventually rupture? Can I just leave them alone as long as they don't leak, then replace them when I'm doing something else to the bike, e.g. I replaced the internal hose when I did the fuel filter. (Ouch! $32.00 for a one foot piece of submersible fuel line!) 

I take long rides across the U.S. And like to feel that everything is in A1 Condition.

Hi Tomnel
most of our bikes are at least 20 odd years old and who knows when the lines were renewed. I thought my 85 RT's lines looked ok, but when I took the tank off and removed the connecting lines I could see that they were all coming apart around the ends that go over the fuel tank/rail spigots. Would've a matter of time to get a leak
in the middle of no where.
I changed mine, Auto supermarket 5/16th internal from memory at cheap prices, but must be "fuel Injection" rated.
If you change them go the whole hog and replace the line from the end of the fuel rail to the Fuel pressure
regulator (have to take the airbox bottom off for this, looks hard but even I have managed it about 4 times so far)
If you get in there you may as well replace the vacuum hose from the last Throttle body to the bottom of the fuel pressure regulator, easy job once the airbox is out of the way. Then you can ride with confidence.

So find about 1 1/2 hours one day and do it. Don't forget to ask questions if you're not sure.(get all the hose first)
Good luck
RT

BMW are quite cheap for the genuine fuel line, I bought a length for €19 which I think is about $15. Replace them all as you say, they do perish where they go over the spigot and while you are doing it make them a little longer so you can lift up the tank to access the electrics and coolant without taking them off. If the bike has been sitting they will harden and then a few tank off services will leave them very prone to failure. A fuel leak under pressure near the engine and exhaust is no fun.

92KK K100LT 193214 wrote:€19 which I think is about $15.

More like $25

the.postman wrote:

92KK K100LT 193214 wrote:€19 which I think is about $15.

More like $25

True. We have funny yoyos over here but my mistake. I have 2 lengths of the stuff in my shed. Replaced them on LT and forgot there was enough left to do the RT. Bought another one for the RT along with service kit and a load of bits then when putting the left over bit from the RT in its place there was the leftover from the LT looking at me..

Know how you feel after years of fixing bikes/cars (but not chain saws or mowers) I have almost 2 of everything.