You need a shouldered pin and do it in a press, OR, you can cheat it, and just put a bolt, nut and a washer on each side that fits the OD of the opening... So it seals the powder out and keeps the rubber bits in shape..
YES, they will get VERY soft during the heat cycle, no, they wont melt, and when it cools, it should be fine...
Good luck
Thank you RetroSBK,
I did it like you said, and it is OK, rubber is well, parts are great and Bike looks better then before (at least I like it

). Here some pics......






