Re: Johnson TD20 / TN26 etc. – T-shooting Part 2

[legendre]

Quick question..

This motor has a small copper tube w/ fittings, that runs from the top of the low-speed carb body (on the case), then makes a 90′ bend and runs to a port in the bottom half of the case, near the top of the motor. This port passes though to the upper crank main bearing, where it communicates with a helical grove in the bronze bearing shell.

I’ve assumed the sole purpose of this system is to supply cool fuel / oil mixture to lubricate the upper main.. the vacuum produced in the case causing some of the mixture passing through the low-speed venturi to be drawn up through the tube and into the bearing.

Is this correct? Does the system serve any other function?

If the 90′ tube were blocked (or missing) what would be the result – aside from the obvious consequences of loss of lube to the bearing?