How much did you heat them and how fast? If it’s too low and slow it gives the bearing time to heat and expand which doesn’t help. Pre heat oven to 350 and put it in for 15 minutes. You’ll need gloves to handle it and it cools off quick so set up everything before hand and work fast.
You have to move the inner spacer to the side to expose the inner race of the bearing, then use a drift punch to pound on the inner race. If the bearing tilts you need to move the spacer to the other side and pound it again to straighten it out. The hub has to be supported with something solid and you have to hit it hard sometimes depending on the fit. On some you can actually do it cold.
When you put the new bearings in DON’T FORGET THE SPACER LOL.
Hope that helps,
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience