Bike runs hot at stop lights. Begins to lose RPMs, and eventually cuts off if I do not give some throttle. I have checked for EVERYTHING I can think of. The thermostat, water pump, and radiator pass inspection. Replaced the radiator cap, bled the system of air, put new coolant, replaced the head. I'm just stumped. I just placed automotive fluid into the system to try and clean any blockage that may interrupt flow of coolant. I don't know what else to try. The fan cuts on at halfway, and the temp just starts going up from there. Just put engine ice into the bike to see if that has any dramatic effect. Also,I try not to ride if the outside temp is over 85 degrees. When it's 90-95, it's impossible to ride without the temp gauge climbing too high.

 

Sounds odd to me.


Check the hot side of the water from the engine to the radiator. When the bike comes to temp it should kick the thermostat open and send water to the radiator. Also when you installed your new thermostat a lot of times you have to push on them by hand to get them broke loose from the manufacturing process. If you didnt do that there is a chance that it is stuck like the one that came out, causing your problem.

 

I didn't replace the thermostat, :/ the old one works perfect. Every process in the cooling system works properly.

 

The majority of my experience comes from cars so I am speaking from that.
You say the coolant is good. The fan is comin on...so the thermo fan switch and fan motor are okay. The next thing to check s the fan blade. Make sure it is sucking air past the radiator. If that is fine, your problem more than likely is circulation.
How did you test the water pump and thermostat? The thermostat should open when placed in very hot water (200^ shoud do it) and close in cold water.. If you can't visibly see this happen ending.. Change it. You are right there anyway.

The water pump can fail in a few ways.. Yes the seal inside can blow causing coolant to go out of a weep hole or similar.. The mounting gasket could leak, but sometimes the impeller inside separates from the shaft.. It might be spinning much at speed if at all.

I hope this helps some as it has been a total PITFA to type this out on my iPad.

 

He completely took apart the pump assembly, no issues. As far as that fan issue, I don't know.

 

And the thermostat was tested on every way imaginable.

 

Since you went to all the trouble to take the thermostat out, why not just put a new one in?

Make sure the fan is pulling air through the radiator.
Check the coolant temp with a thermometer to make sure the gauge is correct.
Have the radiator checked for HC. Could have a cracked head/block or a leaking gasket.
That's what I would check...

 

just take the thermostat out all together for test purposes. That would eliminate that discussion right then and there.

 

What about just flushing out the cooling system with distilled water.

 

Well, I just took my bike out for a ride.
It did good just riding like usual. I got it nice and warmed up.
I pulled back up to the house to see what it would do sitting still in the heat.
It's weird. The guage was at halfway when I got off.
Then, the fan cut on after about 30 seconds of sitting still.
The temperature never went up, but my RPMs started dying.
It is usually at 1500, but it dove down to 1300.
Then, while it was idling at 1300, it would dip down to about 1150, then back up to 13.
It would dip down like that every few seconds. Then it started idling at 1200 and would dip down to about 1000 every few seconds. That's when I cut it off. It would have eventually stalled had I waited about 2 minutes.