Hmmmm, says me. Fifteen minutes and the MacHeads haven't jumped on this. O.K., here goes;
The McCulloch 605, 610, 650 and the redressed counterparts sold by various retail outlets uses an automatic oil pump that is operated by crankcase pulses directed against a diaphragm that moves a piston. The manual oil pump is operated by forcing the pushrod against the pump plunger.
To adjust the automatic oil pump outlet turn the adjusting screw counterclockwise to increase oil flow or clockwise to decrease oil flow.
These saws ain't beauty queens and are fairly reliable. I have several, no make that four of them. Kinda heavy for a 60cc saw but these were one of the last good McCullochs produced before the owners of the name started producing, junk. Sorry but that about sums up what is produced under the McCulloch name nowadays. The 600 series family can be summed up as;
Built like a tank,
Ugly as sin,
Heavy as :censored:,
Great Ole saws.
There may be some dealers that can get the replacement diaphragm and O rings for the automatic pump. Hope this helps.