Can I ask a question for ROTAX 912 ULS?

This works. Since most don't have thermostats the system is open. It still works with thermostats. So put a pan under the lower right side of the radiator and pull the hose off and catch the coolant. Then remove the expansion tank cap and more will drain out. I drape a rag over the hose and radiator fitting to stop any spray during the next segment. I cup my hand over the top of the expansion tank (you can use a rag) and use my air compressor air to blow down through the system. At this stage the system is wide open and no back pressure.  All the coolant will be blown out of the system. Then you can just remove the reservior tank hose and allow all that coolant to drain out. You can then use a rag down inside the reservoir to wipe out any residue coolant and or debris. Then just refill them. This whole process just takes a few minutes.

When I do hose changes this is what I do so I don't get coolant all over the place when I remove coolant hoses.

Dear Roger

Thanks for your information. It will be useful for me.

I want to do that perfectly, so study more and more with your guidance.

Thank you very much.

Best regards.