My son has the 150F and it sure doesn't feel heavy when riding it. It has a nice planted feel to it. I think it's a great bike. Well built and doesn't have the playbike feel. Doesn't feel cramped like the TTR125 or KX100. It is lacking in power but when riding the tight stuff, it's totally fine.
I am very impressed with the bike.

I love my CRF150F, but it is a heavy bike. I don't really mind the weight, until I dump it in the woods during my 5th lap of a Hare Scramble. Then it really feels heavy. BUT, the electric start is a decent exchange for not having to kick start it after picking it up after dumping it. If you can keep the bike upright, the weight is less of an issue.

Hey everyone I'm Sarah new to the site. I had a CRF 150f as my first major bike 18 months ago and I loved learning on it but picked up the sport much quicker than I anticipated lol and found it wayyy to heavy and wanted to get more into MX so sold that and picked up a KTM 105sx which is much lighter but a lot more power!!!

I really don't know much about KTMs. Is that a 2 stroke? Is it an mx bike or set up for the woods? What size wheels? How's it working out for you?

A KTM 105SX is a 2 stroke.