Kickstart Spring

I'm sure this is something stupid.
I've just started on a new motor, mostly new parts. I've fitted the kickstart shaft to the casing but it won't turn as the spring is catching on the ribs around the inside of the boss.

GP casing, shaft and spring. The kinked in end is in the shaft as described in the book.
What am I missing?
I've just started on a new motor, mostly new parts. I've fitted the kickstart shaft to the casing but it won't turn as the spring is catching on the ribs around the inside of the boss.

GP casing, shaft and spring. The kinked in end is in the shaft as described in the book.
What am I missing?