Kywoo Tycoon 3D - Impossible to print after using PETG

[Bikeracer2020]

You can cut a piece of new teflon tube, make sure the cut is at 90 degrees at the end and a snug fit against the nozzle.

Ideally you need to convert to a bi-metal hotend with a heat break above the nozzle.in it .

I had the same problem with my Qidi standard hot end, the manufacturers state the hot end is capable of the temp you want, but on enquiring it is not suitable for prolonged use at the higher temp specfied.
I converted mine to an all metal hot end and have had no more problems with the hot end at 250/260 degrees.

There are loads of different bi-metal replacement parts on Amazon, you need to search for one that fits, some screw in with usually a 6mm or 7mm thread or are held in place with a grub screw.