I was replacing my bearings on my bx2750 snow thrower and I noticed on the lower sprocket there was a bolt going throug the sprocket and shaft. I looked at the parts diagram and do not see that bolt. I bought the snow thrower used. I am wondering if that bolt is suppose to be there and if it is, is it suppose to be a shear bolt? If I remove the bolt the sprocket just spins on the shaft. Not sure what is going on!!!