Hello Gents,
I recently purchased a 1988 K75S. upon riding it home, it seemed to bog down and stall out. It wouldn't start right backup( it would crank and crank, but not catch.) After a few minutes of sitting, it would start back up and run like a champ, high speeds, low speeds. After about 5 to 8 minutes the same thing would happen. this happened 4 or 5 times, then it ran great for about 60 miles, stopped for gas, ran fine another 20 miles home. Now I've ridden it a couple of times briefly without incident, then it started doing it again. I thought at first it seemed like a fuel issue getting cut off or something like that. I thought I would start by replacing the fuel filter, so I drained the tank and replaced that. Realizing there was some crud in the bottom of the tank, I cleaned that out pretty thoroughly. I noticed some slight cracking in on of the fuel lines, so I replaced them all while I had the tank off. In removing the air box to replace the lines to the fuel pressure regulator, I noticed the air filter itself was fairly dirty and almost seemed moldy and damp. I replaced the air filter and thought maybe it could have been not getting adequate air intake. After putting it all back together I rode it around for a few minutes and thought maybe I had resolved these issues. I went to take it out for a ride this morning, and I couldn't even keep it running long enough to get it out of the drive. I was wondering if anybody had any other thoughts on this. Could the fuel pump be shutting down, or the screen on the fuel pump intake be clogged?  I would greatly appreciate any input. 
Thanks,
Tim K.

Has it been sitting unused for an extended time?  It sorta sounds like it has.  How many miles on the clock? 

I think I would pull the fuel pump and make very sure the screen is clean and has been put on the pump properly.  I would also check the fuel tank electrical connector.  I could see that causing erratic intermittent fuel starvation. 

It wouldn't hurt to get some Techron Complete Fuel System Cleaner and throw some in the tank to help clean out any varnish that may have formed in the injectors. 

If it were my bike I would take a couple days to do a complete maintenance on the bike; valves, brakes, fork oil, the works.  Get some Deoxit and go through and shoot every electrical connection on the bike.   It sounds like it really needs it.

Yes, it had been sitting for some time before. It has about 32,000 mi. The previous owner had it serviced to sell. At his request they replaced the injectors, fuel sending unit, and cleaned the tank(very poorly). I did notice when I replaced the fuel filter and put everything back together, the plug looked
 like it had been messed around with. I'm not sure why. The first photo is the plug from my '89 K100, the second one is from this K75. the female plug looks as though all of the receptacles were bent in. Is there a way to replace or remedy this if it is my problem?

That the fuel level sender was replaced and the female connector is bodged makes me think that the bike has had intermittent fuel pump cutting out problems. 

I would spend some time checking the wiring to the fuel pump.  Start by confirming that 12 volts is present at the appropriate sockets on the female connector when the start button is pressed. 

From there, confirm that there is continuity from the male connector pins to the fuel pump. 

If all that is good, connect the tank and see if you can hear the fuel pump when you press the starter. 

I would still take the time to pull the pump and check the screen for proper installation and that all the hose connections are tight.

I'm terribly sorry I forgot to follow up on this post. I did check the voltage to the pump and the pump screen, which was clean. The voltage looked good also. After spraying some of the connections with Deox-It I thought I would try it again, only this time I didn't hear the fuel pump kicking on. I checked the voltage and was still getting power to it, so I replaced the pump. Voila! fired right up and has been running great since the middle of July.
Thanks again for your help, Tim