Heavy smell of fuel yesterday so I’ve stripped the airbox out to investigate. 
2 questions if I may gents?
1/ the line going into the top of the regulator swivels as if on an o ring seal, is this correct
2/ I assumed the system would or should remain pressurized even when not rumming. I took the lines off of the tank and no pressure or fuel spray and this could possibly be why it takes a few cranks to get it started ie building fuel pressure. 

thanks all, john

ok got my own answer to question 1, fuel lines loose on both supply and return on the regulator.
Still wondering if the system should stay pressurized though.

If that is lose then I would strongly recommend replacing all the fuel lines. They are probably 30 years old.

That’s the plan Rick. Should it maintain pressure, ok not 36 but atleast some residual?

In theory they should hold pressure for quite some hours but I have found that even 10 minutes will cause the pressure to fall away significantly.
Usually when starting from cold tap the start button, this will make the pump to run for 1.5 seconds and will prime the system then hit it to start and it will usually fire very quickly. My K100 and K1100 always needed priming but the K75 usually doesn't need it if the engine is the slightest bit warm  it will fire almost instantly.

Frustration is just not a big enough word! 
Replaced all fuel lines and now the bike will hardly idle and tries to die if I open the throttle. If I feather the throttle I can get it off idle. It’s worse now than before. Flow meter door is working, no fuel leaks. Return to tank side of the regulator is flowing fuel. Can these injections get air locks? Any idea fellas?

The fuel lines you chose, do they have FI pressure rating? Are there any sharp bends that may be collapsing, restricting the fuel flow? This was a problem for another member here. https://www.k100-forum.com/t13394-collapsing-fuel-return-line

pressure rating is 10 bar so more than enough. no kinks. removed injectors and will check them tomorrow. Will try another fuel regulator I have tomorrow and a different ecu.

nobbylon wrote:Frustration is just not a big enough word! 
Any idea fellas?

How about Exasperation? It has five syllables, two additional vowels and an additional letter.

Give the clamps another tightening, too.

_injectors are all 16.6-7 ohms. will check the spray tomorrow. Fortunately I have the other K to try bits from.

nobbylon wrote:pressure rating is 10 bar so more than enough. no kinks. removed injectors and will check them tomorrow. Will try another fuel regulator I have tomorrow and a different ecu.

question ...you do have the correct orientation of the fuel lines at the tank ?

the tank rear spigot (high pressure) line does go directly to the fuel rail ...the front tank spigot is the return from regulator output (top fpr spigot )

fuel lines are connected correctly yes.

Fuel filter Blocked?? Fuel escaping from the O ring at bottom of tank?? Just clutching at straws. Cheers Tom

Thank you to all for suggestions.
Normality is restored and this may help someone. After changing the injectors, swapping out the ecu and air flow meter the bike just would not pull away from idle, bucking like a bronco.
I don’t know why I did, possibly in an atempt to check if the line was pinched but I squeezed the FRONT fuel line at the tank and held it closed for a few seconds while attempting to rev the bike and it just burst into life again. Starts instantly on the button and throttle response is now instant! Rides and pulls clean once more.
Could it have been an air lock in the pump, filter, fuel reg? 
Camping is back on with the RS! Plus with the new fuel lines the fuel smell has gone 

My guess: the one-way valve in the fuel tank was corroded partly closed and squeezing the tube built up enough pressure to shift it. If the tank starts rattling, the spring in the valve has broken and what you can hear will be the ball bearing being pulsed by the fuel pump. It's not a show-stopper but when you remove the fuel line to fix the (hypothetical) rattle, remember to either run the tank low or empty it first.

Oddly enough, I have one of those valves on my desk in front of me!

thanks for the info Dai. Rebuilt the silver one back up and they both start and run fine so far.

I suspect you may have a failing fuel pressure regulator that was not providing enough/consistent fuel pressure at the injectors.  This may have been caused by the dump valve inside the regulator being stuck in the open position.  Pinching the return line may have created enough back pressure to seat the valve in the regulator while boosting the pressure enough to provide the fuel flow through the injectors to allow for proper acceleration.

If it were my bike, I would be thinking seriously about having a spare regulator on hand and being prepared to install it the next time the problem appears.  Of course, having a spare will insure that you will NEVER have that problem again.

Point-Seven-five wrote:I suspect you may have a failing fuel pressure regulator that was not providing enough/consistent fuel pressure at the injectors.  This may have been caused by the dump valve inside the regulator being stuck in the open position.  Pinching the return line may have created enough back pressure to seat the valve in the regulator while boosting the pressure enough to provide the fuel flow through the injectors to allow for proper acceleration.

If it were my bike, I would be thinking seriously about having a spare regulator on hand and being prepared to install it the next time the problem appears.  Of course, having a spare will insure that you will NEVER have that problem again.

I agree wholeheartedly with this.

I had what I thought was a fault regulator so bought one. Of course that meant the problem fixed itself.

Does having a spare K100 count? I will start them both from cold in the morning but hopeful it’s sorted.

For best results, it really needs to be in the tail cowl.