How to rebuild the kernel for the network install

[Joshua C.]

As the title says, I'd like to reinstall fedora 15 with the netinstall
image because it's about 100mb (kernel and initrd) instead of the
install dvds. My problem is that those files located in
http://download.fedora.redhat.com/pub/fedora/linux/releases/15/Fedora/x86_64/os/isolinux/
have long been outdated. As you can see the kernel is only 3.7mb and
the initrd almost 94mb. How to rebuild them from the latest
kernel-2.6.40.4-6.fc15?

--joshua