Oil tank breather 1956 Dominator

Later slimline oil tanks had a "Froth separator" tower on the top, don't know when they were introduced. Occasionally turn up at jumbles. Although the 2 tanks that I got were earlier plain ones, both had previous repairs with the top bracket welding back on from being too tightly bolted up, and so suffering from vibration fatigue. Shame, because both had reasonable chrome, but obviously messed up by the repair.

If there is room under the saddle  you could make up a tower in 22mm ( or bigger) copper plumbing tube and  cut a hole in the tank  ,solder in  with plumbers solder  and solder in 2 new connections  using 3/8 gas ( 10 mm?) copper to take the incomming  breather as low as poss and the outgoing breather ( to  chain) in a higher position.  I did this on my 99DL  which has a steel tower/filler as std. Cant say anything good comes out for the chain and short journeys will make condensation in the tank needing regular oil changes . 

Richard, I'm assuming 99 DeLuxe....

My 650SS has a breather in the top of the oil tank. I'm not certain when this mod came in for the slimlines  but my guess  is 1964 when several changes were made:

12 v electrics

5/8 x 3/8 rear chain

Grommet in the primary case to adjust clutch center nut without case removal. 

For my 99 and Dommie racer; I decided I'd had enough of oil dropping on the floor if any oil left in the sump on starting. The solution was simple, as seen in the pictures: A large clear plastic tube that raises to the rear of the bike. The excess oil never reaches the exit and eventually goes back to the sump.