My recent trip down south from far North Coast NSW over Xmas was pretty uneventful apart from the joy of being out on the open road. However on two occassions it seemed my old girl got a bit hot and bothered.
Spent a few days riding around Sydney CBD and inner burbs and on one day which was a scorcher, I noticed a lot of heat off the engine. The fan was kicking in also which I find it doesn't often do. The major problem was that the engine started to rev at idle. Instead of the normal <1000rpm it was over 2000rpm. Also something very weird was that while the engine was hot the engine would start as soon as I turned the ignition switch on (no starter button used).

Happened once again as I was returning home last week. Hot day again, high 30s. Freeway mode (110-120kph) no significant hills. I pull in for a pit stop... over reving on idle plus the starter issue. Took a long break for lunch in the shade to let her cool down... all good for the remaining 5 hours.

Apart from this, the engine is running very nicely. I'm thinking thermostat as the likely cause of the overheating but why the excessive idle revs and starter issue?? Anyone got any thoughts on this?

I would say that it was only heating as much as they usually do on hot days in city traffic. The fan is cutting in and pulling the temp back down its working as it should. My K1100 will get hot very quickly in those situations and as soon as you get moving the temp comes back down.
High idle is possibly the result of a small leak in the inlet tract.
Starter problem is most likely a permanently down start button, I seem to remember you had a modifies starter button. If it is permanently down then that will happen and because the system is designed so that the starter cant work at over 711RPM then the starter motor disengages after it starts.

I wouldn't have expected it to overheat on an easy freeway trip even tho it was a hot day. No problem with the fan cutting in and it's done that before in city traffic but really wonderering about the high idle which is something new.

"High idle is possibly the result of a small leak in the inlet tract."... are you talking about TB rubbers? How is this affected by the heat?

Correct. My start button has no inner spring but other than the situation I've described above it works perfectly under normal conditions. When the engine cools down the starter button works fine.

Running lean at idle will cause it to rev higher as the atmospheric temp and engine temp goes up until it gets to the stage where runaway happens and the exhaust pipes get red and occasionally a mild steel pipe will pop a hole it gets so hot.
You may find that is where the extra heat is coming from.
Is the radiator clean without any dirt or feathers stuck in the outside. I had my K1100 overheating and found that there was a huge accumulation of dirt after blown fork seals dumped lots of oil in the fins.

Thanks Rick
Radiator is totally clean and in good nick. Also, it's recently had a flush with Mukowt.
I need to check air intake for leaks?? Been on my list for a while.
Cheers

have a similar issue

and now have a new fpr ...with pressure gauge

will measure the current pressure  before modification ...thinking itll be running low on pressure ..ie lean on mix   I guess the golden pipes is a telltale of the heat being generated by the lean mix

the rubbers seem to be the most likely location of leaks given past history of many members  nigel

given that the breather tube to the crankcase is in good condition

I've had a cursory check of the TB rubbers (top and bottom) and they look ok but a couple of the rubber caps look to be perished. I'll replace those. I've noticed SuperCheap Auto have packs in different sizes.
But I really need to pull the throttle assembly apart to properly check.
Replaced crankcase hose about 6 months ago.
I've sprayed around the TBs with alcohol (brake cleaner) while running but no change in revs.

Re your FPGuage charlie. Is that measuring the pump pressure?

Cheers

well I guess if I pump it up to 3 bar  on a t piece  it shouldn't flow but measure the current regulator pressure in circuit ? does that make sense ?

cheers

That should work but 3 bar sounds a bit high for regulated pressure