Author: Big Aholio

Rigi

OK, here’s something you might want to know if you own a Knucklehead……The “tins” that the valve springs are inside of need the rocker oil to flow back to the timing case… This is done by using crankcase vacuum… The vacuum is present in the push rod tubes when the pistons are going up in their bores..

Each valve has it’s own isolated valve tin chamber..  Each chamber has a steel tube that connects to it’s rocker arm box (aluminum knuckle)..  So as vacuum pulls from the push rod tubes it is also present in the rocker boxes..  And because each valve chamber has a tube connected to a rocker box, vacuum is also in the little tubes and tin valve chamber…

Because pressure can flow into  each exhaust valve tin via the valve guide.. Vacuum can pull any oil in the valve tin chamber into the rocker box..

Because there is vacuum in the intake port and valve guide, the vacuum in the camber is applied from the little tube AND the intake guide….This results in no oil return in the little tube……Until a small 1/16″ vent hole is introduced into the valve tin chamber..  Then the oil can be sucked into the rocker box from the intake tin..

So, one small hole in each intake tin… No holes or leaks in the exhaust tins..

A bit of grease on the push rod tube seals helps seal the vacuum within them..

Remember each of the four valve tin chambers are isolated from each other.

Getting the proper oil return from each chamber is interesting and frustrating.

Check the chambers for leaks can be done by pressurizing the crankcase and using

soapy water on the tins… If  you see bubbles… air is escaping… and is probably a

vacuum leak when the engine is running….

Smoke ’em if you got ’em……..