if its a K301 Kohler use a 1 3/8 i.d. pipe 24-28 inches long.
You can get a K&N from Stens that fits in the stock air cleaner
housing or get an adapter from Zach Kerber or Vogel mfg. and use
the 2 7/16 hose clamp style one. May be other options as well but these
are the ones I know of.