Hi Bob,
This might sound daft but the injection pump is not designed to pump oil at high pressure/high volume to the bearings such as you would have on a fourstroke motor. The only pressure resistance it has to overcome is a very light spring in the check valves on the crankcase. Don't forget this is a total loss oil system with the oil being burnt in the cylinders. It's an oil 'DRIP' pump' rather than an oil 'INJECTION' pump which suggests high pressures.
It gently pushes, rather than pumps, slugs of oil to alternate cylinders via the crank chambers. The only pressure it can produce is generated by a spring at the end of the worm wheel plunger, which slides the plunger back into the oil pump chamber and expels the oil at low pressure, via the distributor, to the crank chambers. The plunger is then retracted by the cam on the worm wheel pushing against 'Rod C', ready for the next stroke. If I remember correctly the oil (or a bubble) moves forward about quarter of an inch in one of the the oil lines for each stroke of the pump. Have a look at a pump cross section in the manual to get a better idea of how it works or better still take a spare one to pieces. They are pretty reliable, I have never heard or read of one failing.
To test one, set it up on a spare side cover with an oil supply, turn the control lever to max and spin the plastic gear. As long as you see a small slug of oil oozing out of alternate outlet unions it should be OK.
That grey lump under the right carb is a clever piece of kit and its only now, 47 years after I first had GTR that I have got my head round how it works. Would still have to use Graham Weeks' article to set the plunger stroke though.
Brian.
