A motor truck under s. 340.01 (18) (a) 1. registered as a farm truck under s. 341.26 (3) (a) may be used for personal and family purposes if the primary use of that motor truck is for purposes specified in s. 340.01 (18) (a) 1., except that a registered farm truck may not be used in furtherance of any nonfarm occupation, trade, profession or other employment, including commuting to or from the place of such nonfarm occupation, trade, profession or employment. A motor truck under s. 340.01 (18) (a) 2. may not be used for personal and family purposes. This section does not apply to dual purpose farm trucks registered under s. 341.26 (3) (am). Any violations of this section are subject to the penalty prescribed for violations of s. 341.04 (2).