I don't know if it's overheating, or just overflowing...
After riding for a few minutes, the coolant starts to overflow.
I don't have any gauges yet (got the bike that way)
Over all, the bike seems to be running great, except this.
Currently, there's no thermostat, a new radiator cap, and I'm running Engine Ice.
I have flushed out the system.

Running low on ideas...

it's a '91 600, f2

 

no thermostat and it's still overflowing like that? i think you should doa pressure test of the radiator and also cap to make sure it's not letting air out. if the radiator is not pressurized, the coolant would boil faster than it should.

 

i just replaced the cap. and i checked the two mating surfaces to make sure it was sealing.

 

The only thing I can think of is that maybe the replacement cap does not have the same pressure rating as the original. Most other problems would emerge as soon as you started the bike since the thermostat is gone. It would seem like you just have a pressure problem once the coolant is getting hot and expanding and/or boiling. I'm sure you've checked to be sure the coolant mix is right (if it needs to be mixed, I have no experience with Engine Ice) because that is important. If it's not the cap, you may have a blockage in thesystem somewhere that is letting pressure build on the front side and overflow.

Who removed the thermostat? If it wasn't you, your going to want to make sure that they did the job correctly because your bike would do this if the thermostat never opened.Without gauges, this would be your only indicator that the bike is overheating. Sometimes people think that "removing" the thermostat means simply disconnecting it, butas some thermostats will stay open when disconnected, others will stay closed. If it is indeed still on the bike, tryhooking it back upand seeing if that helps.

Good luck and I hope you get it going.

 

the thermostat is gone.
the replacement cap is oem.
engine ice doesn't get mixed.
The coolant seems to flow thru everything.(the radiator gets evenly warm)
i hope to have the gauges replaced in a week or two. But either way, I can't figure why it would be overheating or overflowing. It's all stock- exhaust, carbs, etc.

 

Warm the bike up. See if the fan kicks on when the bike starts to overflow. If the fan doesnt kick on unplug the sensor in the radiator and touch the connector to the frame. The fan should turn on. If it turns on when grounded bad sensor. If it doesnt then bad fan or no power to the fan.

 

did the previous owner remove the tstat or did you do it? he probably had an overheating issue too and just tossed the tstat out. i still say pressure test the system.

how long does it take before it starts to overflow from a cold start?

radiator will be warm as it's next to the header. how does the return line feel?

 

the tstat was gone when i got it.
the fan switch is bad; fan wired to come on with ign.
I can ride the bike about ten miles without issue. After I shut the bike off, it takes about 2-5 minutes before it starts overflowing.
return line feels fine, not cold, not too hot.

thanks for the help; I'll see about a ppressure test next week.

 

Ive had problems when hard wiring a fan to the ignition like you have on your bike. It can burn out the R/R. Its cheap to fix and well worth it in the long run