I've got a 1985 K100rt, that I bought as a non runner, as it kept flooding out and  got it running after cleaning the temp sensor and ran ok for a while revving out ok, but wouldnt idle. So I put new rubbers on the injectors as they were blowing around the seal where they sit in the holes.
changed the oil and filters ran it up, with new plugs and leads and was ok. Now it dont want to start, it fires and wont pick up. I noticed inside the tank that the fuel filter had been bypassed and the fuel line is connected straight to the pump. I removed the pump today to check the gauze filter to see if it was blocked, and its ripped and split, and noticed that the end of the pump where the gauze sits looks like theres something broke with a hole and should there be a pipe for the pump to suck or pick up with? Is this correct with them? Also should the pump tick all the while when the ignition is on or only when the engines running?
Would be grateful of any advice please as to what to check for next, Thanks Steve.

The pump should run when you press the start button, and continue to run
when ECU reads the signal from the hall sensors that the engine is turning.

When doing starting attemps, you should hear the fuel pump running
~1,5 Seconds after you have released the starter button.

Next step...I would say, is depending on how your plugs look like... wet, dry.

Thanks for that Inge

The hole with the spring suppose to look like that, it's the pressure regulator for the pump itself.



This is the pump, fuelcooled  

Thanks for that, had a look at the pressure relief valve on the tank today and that had some dirt in it, so I've cleaned that and the inside of the tank, so I'll put it back together and try it again and will keep you all informed.

Whereabouts are the hall sensors located as I've read other owners starting problems and people say check these for good connection/ contacts as they could be corroded? Thanks again

The hall sensors is under a T shaped cover in front of the engine, the
connector you find under the tank (front/right).
In the troubleshooting guide at the portal you find more info, and how
to test.

Thanks again Inge

I got the bike running at last and the problem was the return valve on the fuel tank was blocked and not letting the excess fuel back in the tank.
I cleaned it all through and now seems to be starting and running well, 
Will see how well when I take it for its MOT on Saturday, Thanks for your help. -o:

good solve

glad to hear its on the road again

not often heard of the return valve failing ...and becoming blocked ,,,could explain some unsolved mysteries

cheers ...ride well