Mk2 Conrods, Spray Holes and Oil Pumps

You have 2 options . option 1 ,  low pressure system where you have the parts. The engine was designed for this.  All you need to do is block the rod holes with the shells . Works OK if pump in good order, .pistons fitted with enough clearance ,drive side carb set to run with a size up in main jet.A 650 pump not a dommy one.  Valve gear oiling a bit borderline unless you change the return bias.   Option 2. fit a PAIR of 6 start gears and all the other bits including better oil rings . Commando Inlet guides with seals and better breathing ,check oil ways for size . As motor not designed for this expect to get extra oil flying around in timing area possibly into mag  and leaks from other areas ,possibly some sooty plugs and   occasional exhaust valve burning from too much oil . Or you may be lucky !. 

Hello again Kit - Bob is quite right it saying that you have a few options.  Remember that,, as has been written in many Forum topics over the years, many of the modifications to the 650/750 oiling system complemented or corrected other changes.  Changing the oil pump, pump gearing,  oil distribution and oil scavenging holds many pitfalls.   The later engines in 1966/67 that saw the culmination of all the required changes were based on crankcases with more and larger oil circulation and scavenging galleries that are not included (nor possible in some cases) in your 1962  crankcases.  Fitting the stronger late con-rods is a good idea but as Bob points out the big-end shells may need inverting to block off the oil spray hole in the rods.  If you are going to swap to doubling the oil pump speed and continue to feed the rockers etc from the scavenge return to the oil tank you may need to fit the later twiflex type oil piston rings, or fit a restrictor in the rocker feed pipe.  You say that you are going to get an S-type pump.  It surprises me that neither of your 650 engines has this pump when they were fitted from new in 1961/62.  Let me also remind you that the original 650 engine ran flat-out in 500 mile races without needing changes to the oil system.  So your other consideration is obviously whether or not to feed the rockers with big-end pressure .......If you do so, as Bob points out too much oil in the wrong places can be problematic as many early Commando owners will testify.   I do not recommend going this route without late 650SS or Mercury crankcases.  Much is written in the DSNs and other Technical service directories and there is too much to reproduce it here but if you stick with the SS pump, 6 -start gearing, with twiflex rings and strong rods, with upside down shells you should never need another rebuild.  Good luck, Howard         

The scary part of the above is the pistons. If they are original 650ss pistons then make sure you have the original 650ss pins to go with them. These will fit the rods you have perfectly, earlier pins would most probably fit giving a false sense of security but they will not have the clearance in the small end, there is a difference in pin diameter though a very small one it could lead to a seizure. 
 

I certainly struggled trying to fit 99 pins into 650 pistons many years ago , and my current 650 project has stalled with suspected tight pistons making it very difficult to turn over .