Hollow Rear Axle For Bobbins

[16 Scrambler]

I just bought a 2016 Scrambler. I tried to use a bobbin the goes through the axle. It goes in left side but stops about 1/4 inch from right side (chain side). Is the hollow axle tappered? I am wondering if there is rust in there but did not want to start drilling it out if there is a reason it gets narrower on that side

 

[Charp]

I got the same thing for my street twin. The bobbins are shaped differently for the right and left. One side sits a little recessed in, so maybe try reversing which side the bobbins are on.