does it seem like the engine really is hotter ? if so....maybe...
....the waterpump is failing to deliver as much as it used to
....radiator plugged up
....possibly thermostat has drifted to a lower setpoint over time.....
....line to the overflow reservoir is plugged and you are low on coolant in engine

if not maybe ....the temp sensor is failing??

good luck..here is your coolant schematic

1999 Kawasaki VULCAN 1500 CLASSIC(VN1500E2)US OEM Parts, 1999 Kawasaki VULCAN 1500 CLASSIC(VN1500E2)US OEM Motorcycle Parts - BikeBandit.com

 

DanG

It is quite warm lately. At these temps any little extra stress is gonna hot up that engine. You could be dealing with almomst anything. My fan is running alot these days and it would be tough right now to define too much. easier determination when its cooler.

 

DanG

It is quite warm lately. At these temps any little extra stress is gonna hot up that engine. You could be dealing with almomst anything. My fan is running alot these days and it would be tough right now to define too much. easier determination when its cooler.

+100 % ^
With the heatwave most of us have been experiencing, it's totally normal to have to fan kick in a lot. Mine even kicks in for a few seconds after I've shut the engine off. It has always acted like this on super hot days.

 

As long as the fan is turning off sometimes, it's doing it's job. If it never turned off, that's when I'd worry.

 

As he has 48000 mi on the bike, I figure he knows when it is something other than hot weather...?

 

As he has 48000 mi on the bike, I figure he knows when it is something other than hot weather...?

+1

It may be nothing, but after all those miles, and the bike is acting differently, it is something to at least check out. There may be nothing wrong, but you'll know more after you check it out.

 

Eleven years and 48K miles - I'd start with a good old fashioned radiator flush. Cheap and can't do any harm.

This just got me thinking - do our bikes have water pumps? I suppose not in which case silting is an increased possibility.

 

I know you are getting more questions than answers here, but have you been maintaining the cooling system? How often have you changed the coolant and have you used special motorcycle coolant that has been pre-mixed with de-ionized water? After that many miles, some clogging of the cooling system might be occurring. If you've been maintaining it - then I'm thinking it's not the radiator or water pump - but maybe the hotter weather or a change in the thermostat or sensor for the fan.

 

Eleven years and 48K miles - I'd start with a good old fashioned radiator flush. Cheap and can't do any harm.

This just got me thinking - do our bikes have water pumps? I suppose not in which case silting is an increased possibility.

Our bikes do have water pumps. The cover is on the right side of the engine, toward the front. It's kind of half covered by the front exhaust on the 1600.

 

1) Flush the system
2) Check for air trapped in the system
3) A lean condition makes it run hotter, how are your plugs? When was the last time you ran fuel cleaner through it?
4) Add some water wetter or other coolant additive
5) If you don't face freezing temps switch to a 25/75 coolant/water ratio instead of 50/50. I'd recommend running the additives though to maintain the same degree of corrosion prevention.