The bike has 40K miles on it and is running great. I will change all the rest of the fluids I haven't already changed, and was wondering if I should change the fuel pump. How does a fuel pump going bad manifest itself on one of these? 85 K100RT...

"Running great" is the key phrase. You could change it, but why?

It's not a part that is routinely changed - only if it's giving trouble. 

If you have doubts, remove, clean and replace the pre-screen filter at the bottom of the pump, replace the in-line filter inside the tank if you don't know when it was last replaced. Otherwise, "if it ain't broke . . . "

Bill

It may well be true that it's not a part that is routinely replaced but, truth to tell, it does have a finite lifespan.  A catastrophic failure on the road can be damned inconvenient.  After market pumps are available for not so much money, so why not change it out if it has some miles/kilometers/years on it?  I did just that, for no other reason than peace of mind. 
My K100RS is running GREAT!  At 40K miles, I'm prepared to believe it's just hitting its stride! 

My pump crapped itself last week on my way home from work.

Symptoms? The bike just stopped. Engine died and I coasted to a stop.

Speedo says 105,000k's.

My 2 cents worth...would be get a spare pump and just have it ready if (when) you need it.

I think I'll just replace the filter and clean the screen this weekend (tomorrow) and buy the new pump and keep it in the pannier just in case. I carry enough of the correct tools to swap it out on the road if I get hung up

At 40k its unlikely there'll be anything wrong with the pump but age will deteriorate things like the vibraton damper leaving black bits in your tank which will prematurely clog the filter.

It's been my experience that the in-tank pumps will die without warning. It's happened twice in my old truck and once to my buddy's oil head when we were far from civilization.  When something like this:
http://www.ebay.com/itm/331387290009?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

is so cheap, and can stowed in the little cubby of the K-bikes, it seems like prudent, economical insurance if the installed pump is old.

Changing them out on the road is simple only if you have one to replace it!

The inside of the tank looks brand new. I am unsure if the original owner replaced the pump but will ask if I ever see him again.

brickrider wrote: When something like this:
http://www.ebay.com/itm/331387290009?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
is so cheap, and can stowed in the little cubby of the K-bikes, it seems like prudent, economical insurance if the installed pump is old.

This is really cheap but ..... an OEM pump push 66PSI and this one is only rated for 43PSI.
It will work, but the pressure of the pump is near the operating pressure for the EFI (36PSI). If this pump lose 15% of its power, it will be near the end of its life.

Still good to have a cheap unit for emergency.

I just decided Ill change it out and keep the one in the tank for a spare. Better piece of mind. I am also going to replace the filter and packing. Is it as easy as it looks to remove and replace everything>?????or are there things / tricks I should know? Anyone done a write up with pics or a video?

It's not difficult at all. But you do need the tools.  Screwdrivers of good quality are essential. You'll need to remove the fuel filler cap without stripping those four screws, and the work inside the tank itself can be a bit puzzling at first.  At least it was for me until I finally discovered that the plastic ring that supports the pump has clips of different sizes.  I tried for the longest time to get it to seat in the support without success before I turned it 180 degrees and it slipped home without more drama. Depending on the replacement pump you select, you may need to change the wiring connectors.  Some use ring connectors on the posts, others use spade-type connectors.
If I recall correctly, YouTube's collection of videos by Chris (?) Harris details the steps to replace the pump.  In any case, it's helpful as a new owner to have a look at his videos - which are numerous - viewing with a critical eye, of course and occasionally trying to ignore his "colorful" language.

I think that 43psi refers to a 3 bar operating pressure. It refers to a PRV at 15-90psi a bit further on.

brickrider wrote:It's been my experience that the in-tank pumps will die without warning. It's happened twice in my old truck and once to my buddy's oil head when we were far from civilization.  When something like this:
http://www.ebay.com/itm/331387290009?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

is so cheap, and can stowed in the little cubby of the K-bikes, it seems like prudent, economical insurance if the installed pump is old.

Changing them out on the road is simple only if you have one to replace it!

I have carried that same pump everywhere I go since last spring.  I can replace it faster than the Triple A can get to me with their emergency truck.

Only advice is to have a couple of spade terminals and crimpers in the toolkit to make the electrical connections.  The pump is useless without them.  This winter I am thinking of putting the spades on with short pigtails to the ring terminals so changing doesn't require any wiring work.

Is the stock pump 52mm in diameter?

yes indeed 52mm is the number

sometimes the length of the pump ...from the retaining ridges that fit in the vibration isolator (rubber ring thing ) can make a difference to when you run out of fuel ... nothing dangerous or suspicious ...just be aware
if your going to store it on the bike ....seal it in a pres seal bag or something to keep out small particulate matter that might lodge in  the roller cell area of the pump ...as they have very close tolerances to operate properly , and any muck can really affect the reliability etc
good luck

When I had a non running K at the end of November I was suspicious about the fuel pump. Anyway decided now was the time to be having a spare and found an OE brand new old stock for about €40, ring connectors etc. Also got the filter. It was about 2 weeks before I could get time to get at sorting the problem and check fuel pressure etc. Anyway turned out to be the Hall sensor which I replaced.

I am inclined to agree about changing out the fuel pump as a precaution, its one of those components that WILL fail and will fail suddenly. Not if. Away from home is not what you want. Toss the old one behind the workbench as a known good spare.

I found one that is rated at the same as stock, same size exactly same look for $85.00 US here so will buy it and swap it in. However I'll keep the stock one since it continues at this point to work perfectly in the pannier in a sealed bag. Cheers all!

Kev