Hi all. Apologies for posting another one of these but...
What I've done. Swapped an engine over in my '84 k100. Used all the parts from the original
engine (injectors, Hall sensors, starter, alternator etc) Original engine started and ran fine, just
had the output shaft death rattle. The new engine cranks fine, starts, but then cuts out after about 2 seconds
of running. I've done all the tests listed in Frogs FI/ignition link. I've changed everything I can think of
including, both computers (under seat and steering head), coolant sensor, FPR, spark plugs, Hall sensors,
De-Oxited connectors, put kits (O-rings, mini filters etc) through all the injectors, checked that they are squirting fuel, cleaned the throttle bodies, put new rubber inlet manifolds and throttle body and plenum chamber rubber manifolds and put in a new breather hose, everything is new or it worked before nicely, including the fuel pump and filter. The only thing I can think of now is if I put the throttle body/plenum chamber manifolds on upside down. Would this affect the running? I'm assuming they fit a certain way. I have been able to get it started and running on about five occasions, (this is after about three days of changing parts and trying) but it runs really rough and I have to keep the throttle open as it won't idle. The choke has no effect. The only way I've been able to get it running is after it fires and before it cuts out is to roll the throttle open. As mentioned, this has been successful on about five occasions. Any other suggestions would be most appreciated. Regards, Dave.
P.S. I also a, few weeks before, changed the original coils (to the ones with the orange caps), as the bike would occasionally run on two cylinders and the tacho wouldn't work, although, it still did this a couple of times after the coil change. I'm at a total loss.

sounds like the timing is out somewhat  dave

was there any cam chain work done ?

and or ..what were the valve clearances like ?

before going into the electrical items .

Cuts out after 2 seconds of running....What happens if you keep your finger on the start button??

Also the fuel tank plug front left of the tank is well known for dodgy connection on early Ks.

Thanks Charlie and Olaf, yes I did put in a new cam-chain, but also checked the timing carefully, however, it's something to check again. Olaf, I believe there's a connector in the relay box that can be used as a replacement? I'll whip that one out and replace it. Thanks again, Dave.

Among the plenitude of K100 starting obstacles, each of these three have emerged occasionally.

• The air box hoses might not be connected securely to the air box.
  
• The vane within the airflow meter housing might be seized. Slight lubrication with a high quality electrical cleaner/lubricant and a gentle prod might be needed to restore its range of motion.
  
• The airflow meter's electrical plug might need cleaning and reconnection.
  

Thanks Laitch, more areas to check out. Regards, Dave.