Indian's crankcase breathing system was always a bit hit or miss. The factory modified it on a number of occasions, but never got it bullet proof. The system basically consists of a small steel disc covering and uncovering a hole between the crankcase and the outside as pressure goes up and down from the piston movement. On Chiefs this happens in the small bronze valve body on the right hand side of the magneto drive part of the cam cover, and on Sport Scouts and 741s the valve is built into the oil pump.

The stock setup was modified for slow speed police duty by drilling a hole through this disc. The reasoning seems to have been that some air would be drawn in through the, otherwise closed, disc valve on the upwards movement of the pistons thus giving a higher crankcase pressure, and supplying the pushrod guides with oil at low speeds. Presumeably the city police used this valve while the highway patrols kept the stock, non-drilled, one. 

For some reason many Indian riders today have the drilled disc in their engine. At today's higher traffic speed that often leads to excessive pressure in the crankcases -and to externally lubricated bikes & riders... 

Fitting a non-drilled disc certainly helps, but the real answer is fitting a Moto Valve. The Moto Valve will pass more air than the stock breather, reducing crankcase pressure build up and helping your Indian live at today's traffic speeds without excessive oil leaks.

The Moto Valve can be fitted to most late model V-twins in the timing hole on the drive side of the crankcase. It can also be used to replace the stock breather valve body on the cam cover on Chiefs (the Moto Valve will pass more air), but so far the best results have been had with the stock breather + a Moto Valve on the drive side. 

We have Moto Valves and breather discs in stock.