Making HMs in Pokemon RBY Deletable

[Vortiene]

I've been messing with the hex entries of pokemon blue to put together a little tweaked version of the game with some changes to make most pokemon obtainable in the first 50% of the game and to make lots of useless moves more useful. However one of the things I'd like to be able to do is to replace HMs with new moves. I realize this can softlock the game if done in the wrong place, but I don't really mind this risk. Is there an address within the pokemon blue rom at which this check for HMs can be disabled? Anyone know of this sort of tweak or perhaps a patch that does this that already exists?

Thanks

 

[longlostsoldier]

I actually just did this the other day. I don't know if it's in the same location, but in Yellow, go to engine/learn_move.asm, and comment out some bits:
@@ TryingToLearn:
pop bc
pop de
ld a, d
;jr c, .hm
pop hl
add hl, bc
and a
ret
;.hm
; ld hl, HMCantDeleteText
; call PrintText
; pop hl
; jr .loop
.cancel
scf
ret

For soft-locking, you can try looking into modifying HM moves like surf and cut to not require a pokemon which will help cut down on the softlock issue. It's been awhile since I did that, but I think the home folder has the necessary locations that need to be modified.