There's not cotter pin, but there is a locking ring that you must pry away from the flat surfaces of the nut ( usually in two spots ) then your socket will fit,
FYI- it a metric socket, and dont forget to make sure the ignition is set to off, or just pull the spark plug wire to prevent the engine from accidently starting up.

 

Yep! That is, if you want to gain uphill speed in the higher gears.

 

If I am not mistaken, you can use a 1-1/4 socket to remove the nut on the counter sprocket. Sometimes, an impact wrench is handy!

 

Thanks for the help guys, that did it. Yes it was the 1 1/4, i used a ratchet because I was to lazy to get the impact wrench out,

Patrick