What are the notches in clutch plates for?

I line them up when installing the plates… I think oil flow channels…

More likely to be fixturing holes used during manufacture, none of the manufacturers specify their orientation, it's probably doesn't make a difference.

I too suspect its to do with manufacturing process. As oil flow channels I don't see how they add access to anything useful, the oil is just flung off the basket anyway

If the OP is referring to the (generally) 3 notches on the outside to the male fibre plates, I've got a few much more precise and finicky Master Mechanic Mates that position the entire stack with those in line, so they can use some little RA ended tools to go down into those notches, then twist said tools to grab the Whole clutch plate stack, straight out of the basket in one go.

I do  (somewhat - I'm No Master Mechanic) ) the same, but generally just use one or two little tools ( almost inevitably just bent TIG rod remnants ) to winkle the whole stack out as one. 

To make you ask questions. 

I don't know, but I bet they are intended to draw oil out of the sump. That surface gets submerged in the oil bath at bottom and a cutout like that would "scoop" some oil to the top each revolution. 

So ... we're not sure 😁

Oh, man! That is a good tip!!

At the speed the basket is spinning the little cutout is not going to scoop much of anything imo. Secondly, why is there a need to scoop oil to the top? It's instantly flung off the basket again.

Most clutchsets I see don't have these cutouts either. I think it's from manufacturing process, maybe so different clutch plates with same diameter, but different size or number of prongs can be processed by the same machine. Just guessing though

Sharp side out?

I thought this was an interesting question so I wrote to Hinson. They replied:

"Those notches are basically part of the manufacturing process and has no bearing on the orientation in the bike. However, we always align the notches as it looks good. Lol."

There ya go! Though I do like Bearuno's tip and plan to use that.

As The Dude said- "New shit has come to light!"

Thx for confirming with Hinson. 

Do you have hands and fingers? IMO you spend more time making your "specialized tool" then just taking out the clutch plates.   

The time savings may be worth it for a factory mechanic, replacing clutch packs between motos.

Yep, I can agree with that. But even then I think just putting a pick/hook tool behind the last plate and yanking out the whole assembly will be equally as fast. I do see the value in having a new stack pre-aligned and ready to slide in though.

I agree, removing the complete stack by hand is quick, but it's almost impossible to align the stack and slide the complete stack in by hand, having a tool to keep the stack aligned during assemble would save time.

I don’t recall ever needing a special tool to remove the entire stack @ one time.

Personally, I am one of those idiots that will spend 3 hours and $20 making a tool for a problem that does not really exist.

I do stuff like that and show it to my brother and he just shakes his head and goes "Man, you could have spent that time going riding!" Hahaha 🤣🤣🤣

Ditto

A lot of bikes have these two finger grooves in the cases to grab the whole pack with your index fingers...   
For sure the CR250R in the photo and the YZ250 have them.