I'm embarrassed to say I cannot find the radiator cap on my gray market mini. The "overflow" tank is fine, but I need to check the coolant level in the radiator. I have a VIO-30 manual that describes there being one, but not where it might be. My radiator is under the right side skin, but I see no filler (or drain for that matter). The fins look clean. The radiator is "tiered" to fit in the confined space. Or maybe there is n oiler cooler sandwiched onto the water that makes it look weird. The VIO-30 claims to not have a oil radiator.
Some applications of equipment I have seen don't have a cap on the radiator itself, the recovery tank cap IS the radiator/pressure cap. Is your cap a rated pressurized cap?
Found the radiator cap cleverly hidden under a rubber flap at the fuel filler. Tank is full, so maybe the thermostat is stuck closed. No leaks visible, fan belt is good. I'll check radiator for dust a little harder. I ran the engine for about 30 minutes at idle and it did fine. Maybe all the rocks are stressing it.
Sounds like you may have an airflow problem. You should see about a 30-35 degree drop in temperature from the top of the radiator to the bottom. I have seen many engines overheat to lack of a thermostat too (pushes the coolant through the radiator too fast.)
Im not sure about b3.. but on my 430 i had to bleed the air out of the system with a little air screw at the top rad hose area. Make sure belt is not slipping. And rad is clear.
It appears it's not actually overheating. I was running it today glancing at the gauge every minute or so, and the gauge suddenly shot up, and the fuel gauge did too. I waited about four hours, and it was still showing max. Maybe a bad ground to the dashboard or something?