I might also add, putting the original plastic/fibreglass shroud on the back of the radiator can also make a fairly big difference in how much air the fan pulls thru. I got a spare 1200 radiator with my 120Y when I bought it, and it had the shroud attached to it. Got bored on a rainy day and put it on my 1200 sedan's radiator. Started it up, and the fan sucked a s***load of grass seeds and leaves out of the radiator fins, so it really does make quite a bit of difference.

Just make sure you have good engine mounts if you install a shroud. If the engine moves quite a bit when torquing/revving you might have to make a larger shroud or replace your mounts, as they have a nasty habit of smashing fan blades and shrouds (the fan is attached to the motor so it moves where the motor moves, the shroud is attached to the radiator, and they dont move anywhere....so 2+2=...)