I had an annoying incident today. Took my oldest K75 (Red), 165,300 miles on the speedo, out to transport a crash bar to a friend for inspection and opinion on salvageabilty. Sat and chatted, friend took off for dinner and I went to leave after him. Getting the riding suit on, ear plugs in etc makes me slow. But when I went to fire up the bike, NADA! It turned over but no firing. Oh the pain. I tried push starting it, I tried cranking until I was afraid the battery would die. I did get a couple of back fires. Based on a previous thread here, suggesting that the fuel pump might be overdoing it and flooding the engine, I disconnected the fuel pump (the connector that comes up at the tank). Cranked but no start. I opened up the tank and changed the fuel filter. Also tested the fuel pump by putting my finger over the end of the hose coming from the pump to the filter. Pump had enough pressure to force my finger off the end of the hose. Reconnected everything. Still no go. After over an hour of trying to get it to start, I got a single very loud backfire. Then I went through all the fuses, all good, pulled the connector to the computer and re-seated it. Then I tried cranking for an extended period. I got one more loud backfire. Possibly raw fuel getting to the muffler. Sounded like the muffler internals were getting blown out. Again tried an extended cranking and got a couple of half hearted starts. Finally one which kept running. I left the engine running, got back in the suit and rode home. No issues, ran like a champ very solid. Got home, and tried restarting it several times. Restarted each time. Went had dinner came back after about 1-2 hours, won't start. Same problem as before. Let it sit for another couple of hours and retried starting. Initially it would start but then die off like lack of fuel. Then cranking for a period nothing.

Bottom line, possible temperature sensitivity in starting. Once started runs fine. Once started and run can be restarted again if done while bike is still warm/hot. After bike cools then it won't start till temperature drops to ambient.

Any suggestions of what to look for?

P.S. I will be traveling in a few days so apologies if I drop the thread for a short while.

First thing to check when it fails to start is whether the spark plugs are wet or dry.
Regards Martin.

Check if the FPR is working well, also the return line.
In between pump and fuelrail should be around 2,5 Bar when pump is running.

Check the earthlines on the bike, there are 2, but for your case, 3.
1; under the tank.
2: at the gearbox.
3; the watertemperature sensor
Ow yes, that bugger is earthed through the engine, loose it a bit and tight it, do that about 5 times.
Also check the connector to the sensor.
(It will not be THE problem, but worth a check, as it is forgotten by everyone )

Check if the FPR is leaking through the vacuumline (will only affect cilinder 3), take it off at the manifold, let the pump run, see if fuel comes out there.

Trying to make sense of this. Ran bike in the back yard till it was hot enough for the fan to come  on. Stopped, restarted fine, waited an hour. Couldn't restart. Pulled spark plugs. All three are bone dry. They are still mostly white as they've less than 5K miles on them. Put #2 & #3 back in. Put #1 on spark wire and provided a ground. Tried starting, no observable spark on #1  but the other two tried to restart. Still need to check the fuel pump etc.

Put bike away as a project for next week. Other things now have priority.

thanks for the suggestions.