I don't run crank bearing seals....take em out the bearing before install.
When I put a new seal in the case, I clean all oil residue off the case where the seal sits and outer edge of the seal with acetone so there's no lubricant to help the seal pop out...kind of like KY jelly vs no KY.....create some friction. After the seal is in, I use a lubed Q-tip to carefully lubricate the seal hole then lubricate the crank shaft upon install. I guess I've been lucky in this area.... I'm yet to pop a seal out.
I see some pics on FB where guys glob motoseal all over the seal and case in an attempt to glue the seal in place.
Doing things like transfer port modification and using crankcase stuffers helps up case compression. This can put added pressure on seals. If you're not racing in organized settings, it's really not necessary to do these things. The out the box modified engines today already produce wickedly dangerous speeds for a motorized bicycle.