This has come up in a few threads so I made this dedicated thread so that other threads can just point to this one. You may have seen the article from BDK here http://www.bdkraceeng.co.uk/Bike1.html#Ignition this is where I started. It states that: "If you measure csa(cross sectional area) of oil loss at rod ie:area of pin minus area of rod inc shells, times 2 for both sides . Plus oil loss for outer main brg(since these are fed together). This is the total area for oil loss assuming the crank is not moving(no centrifugal pull). A rule of thumb is that the supply csa is at least a third larger than the loss csa. This also assumes no 90 degree bends etc. If you look at the oil feed in the btm case it has an arduous path to the outer main and consequently the big end. The oil rises in a 5mm drilling (where the restrictor jets are) and then horizontally in a 6mm hole and then up again at 6mm to the outer big end. The 5mm drilling has to be because they wanted to put a M6 thread in it for the jet. Anyway, take the 5mm hole out to 6mm and then use a thread repair, Time sert or Helicoil, to restore the thread for the oil jet. The reason the main is OK is because it always has sufficient oil and little centrifugal force, however the big end throws the oil away at a considerable rate .Remove more than you are putting in and bang! I have seen hundreds of FZR's with outer b.ends gone. All modified as above sorted them out without fail. " The procedure as recommended is correct but some simple grammar errors make it a little difficult to follow. For clarity here are my corrections based on my FZR400RR 3TJ1. The feed to the outer mains is not 6mm. The final hole is 6mm but there is a reamed section below that (shown in red on image) that is 5mm. First the corrected text: The oil rises in a 5mm drilling for main bearings 2 & 5, where the restrictor jets are (2.55mm diameter), and it also branches horizontally in a 6mm hole and then up again at 5mm to the outer main and big end. The 5mm drilling has to be because they wanted to put an M6 thread in it for the restrictor. Anyway, take the 5mm hole out to 6mm all the way to the bottom and then use a thread repair, Timesert or Helicoil, to restore the thread for the restrictor. The 5mm gallery (shown by blue arrows) is not large enough to feed both the 5mm main & big-end, and the 2.55mm restrictor. As I recall, some forum members have already checked and said that the 250 does not have the same problem. Cheers Blair
