Overheating problem

I hope someone can help me with this problem. Had a Honda interceptor 500 for 25 years it would get hot in the summer but the fan would kick on or drive without hitting lights and it would cool off. Now have a 700 interceptor temp outside 85 degrees ride the bike and it gets hot below 85 degrees no problem stays cool WHY WHY WHY. I checked the fan it works, check coolant fine, but when it gets hot i don't hear the fan kick on. Want to replace the thermostat but not sure if that's the problem. Want to figure it out so i can ride without worrying it will get hot and then stall and have to wait until it cools off before i get going again. Any help would be great and would be forever grateful.

Thank you.

 

Try a new radiator cap first, then the thermostat, both cheap and easy to replace (unlike newer bikes where thermostat is under the throttle body). Make sure you "burp" it after any replacing coolant. Cap maintains the required pressure to raise boiling point. Has your radiator been damaged by a fall on the left side? The neck that hold the cap is very vulnerable.

 

Thanks for all who replied, but no the bike has not fallen so no damage. Will try new cap first then thermostat if it keeps on doing this. Kind of strange, just started doing this had no problems the last few season's. I have read where some people have added a switch to turn the fan on before it gets hot, don't think i want to do that would just rather correct the problem. Thanx to all will keep you posted.

 

I'm a little confused by your description but here's a few pointers on the cooling system. It is intended to keep the engine at a "normal" operating range of about 80 to 120C, preferably closer to the lower end of that scale. Basically you have three independent parts, the radiator cap, the thermoswitch/fan and the thermostat.

The radiator cap should hold about 1.1 bar or 16 psi pressure (caused by the coolant heating and expanding) and that stops the coolant boiling at high temperatures. If the bike was overheating, a cap that won't hold pressure would be a likely cause.

The fan is switched on by the thermoswitch mounted into the radiator. That switch completes the circuit from the +ve terminal, to the fan, to the switch and then to ground (the -ve terminal on the battery). The switch should switch the fan on at water temps above about 100C or 212F, which is normally about 1/2 way on the temp gauge. You can check the fan power by taking the wire off the thermoswitch and connecting it to ground.

The thermostat regulates the coolant flow to the radiator. When cold the thermostat is shut and coolant can only flow around the engine and pump loop, so it warms up quickly. Once the coolant temp reaches about 80C or 176F (usually the bottom mark on the gauge), the thermostat starts to open allowing the hot coolant to pass through the radiator. Once the coolant reaches about 95C the thermostat is wide open and all flow goes through the radiator. Thermostats can fail with age either in the open (common) or closed (less common) position. To test the thermostat start the engine from cold and let it warm up, while keeping a hand on the radiator. If the thermostat is working well, the radiator stays cold for a few minutes, then suddenly gets too hot to touch. If the thermostat is stuck open, the radiator will slowly heat up from the time the engine is started. If the thermostat is stuck closed, the radiator won't ever get hot (but the engine will).

 

i guess it would be a bit easier if you were here to see what i am talking about , but that isn't going to happen LOL. I'm just trying to figure out why all of a sudden the bike gets HOT and what I mean by hot is so hot it wants to stall if I stop at a light you can hear it getting ready to stall. When you pull away from a light you really have to give it the gas. Get home wait 20 minutes let it cool down and it starts like nothing is wrong and off you go until it gets hot again. This just starting happening so I'm going cheap first, new cap then thermostat, buy the way here comes the stupid question and try not to laugh please. I have looked for so long trying to find the thermostat switch and can't see it, was told left side towards the bottom not there. I was thinking maybe put a switch to manually turn on the fan before it gets hot but not sure if i want to go that route. Any way it does have an oil cooler if that makes any difference, I miss my 500 knew that like the back of my hand, the 700 is a little different. Thank you for taking the time to reply, have a nice day.

 

Sounds like it might be your water pump, or thermostat is not opening. Try removing thermostat completely and see if condition persists. If it does either pump is bad or there is a blockage. It should take longer to warm up, keep your hand on the radiator, it should get warm slowly.

 

Just to be clear, there is no "thermostat switch". There is the electrical thermoswitch which should be on the back left of the radiator, and the purely mechanical thermostat which is in the housing on the right side of the engine and connected to the radiator with a big hose. Much easier to access than on my VFR800 which has to have the whole air/box/injection system removed to get in there...

You can check the thermostat operation by hanging it in a pot of water on a stove, and bringing the water up to the boil. You should see the thermostat open at around 80C/176F. You can see the gap that opens between the wide flange, and the plate on top of the spring, in the last photo.

 

Looks like thats the road I'll have to take, will give it a try in a few days, going out of town until Thursday. Will keep you posted thank you so much for your help, take care.