You put the flat washer under the hub as well correct ??
Like i mentioned , if you lay the bike over and remove the small cover , you can see the clutch operate and make sure it is in fact disengaging correctly , but i am guessing it has something to do with the cable slack , where you having issues , the clutch lever should release/grab about a finger thickness from the grip (in other words , when you pull on the lever , you should have your index and middle finger still on the grip , the clutch lever should just touch your fingers when it engages/disengages , otherwise you have the adjustment off , it will have a load on it , so it will be hard to start the bike in gear , but it should not drag enough to try to move the bike
So triple check your cable adjustments , not only at the lever but at the mount on the engine , as that adjustment is done first , then you fine tune at the lever , i prefer about 1/4" freeplay in the lever , where the lever can be moved 1/4" without any tension on the cable
Try that and report back
Here is a 450 install but it should be basically the same procedure
https://www.youtube.com/watch?v=9RBLcaVpLwc