"2 Valve" Rear Cylinder Head
Cooling Tip

 About a year ago, Bruce Meyers advised me to improve cooling in my 944SS by  restricting oil return in the vertical cylinder using a restrictor made with a carburetor jet. Unfortunately, I do not remember all of the details and  now that I want to make the modification. Could he please review it again  for me and others? Thanks for the help! -Jim T, USA

 Bruce Meyers responds:
 Drill and tap the banjo bolts that hold the oil return lines onto the  cylinders. Drill out a carb jet to 1.9 mm and install inside the banjo bolt with red locktite.

 Editor's note: I inquired of Bruce Meyers about this modification. Bruce  responded that "before you (restrict the oil return) the cylinder doesn't  fill all the way - it leaves a bubble of air at the top...  When you  restrict it, it pushes that bubble out."

 Also, since an over-heated vertical cylinder is the prime cause of cam belt  breakage, this is a modification to consider, particularly if you ride your  SS or Monster hard and/or have made heat-producing engine modifications  (hi-comp pistons and/or 944 kit) - D.S.


Mike Cecchini writes:
Since I was re-installing my oil return lines to my left cover anyway, I  figured this was the right time to do this mod to make to improve the oil  cooling on my M900.  I searched around the garage for an unused or obsolete  carb jet.  Not finding any, I went to my banjo bolt parts and lo and behold  I found that a brake banjo bolt is identical to the oil line banjo except  the brake banjo has a hole that is exactly 1.9mm (.078") size that Bruce  recommends.  For the record, the original oil line banjo hole is 3.7mm  (.148").

 The bottom line is to remove the oil line banjo bolt and install the brake  banjo bolt.  Done.

 Mike Cecchini