I have a yz426f with an yz450f 06 carb. I rebuilded the carb since it had a vacum leak. Now it got fixed running great with a low idle. I have pilot jet 48. 165 main. Needle at second clip starting from the bottom. There is engine ice in the radiators with a catch up tank for the overflow. Yesterday i drove 5km at high to medium speed and sometimes slow speed. When i came home the catch up tank was full and he started spitting. The coolant lvl in the radiators i fill just above the fins so not to full i think. It was raining and 9 degrees celcius outside so i think it may not boil over that quick at such cold temperature. Ideas?