Because there are many camshafts and pushrod sets for the

HD accessory market, I frequently hear the following question:

"What is the proper procedure for adjusting the pushrods on

my bike?

The diagram at the left shows a cutaway schematic view of an

adjustable pushrod and hydraulic lifter assembly. Labels identify

some of the components. (Note that for this explanation, no

check valve is shown but it is part of the lifter).

When hydraulic lifter units are first assembled (with no pushrod

present), the compression spring pushes the hydraulic unit and

pushrod seat upwards until the pushrod seat contacts the lower

edge of the retaining ring. At this point the hydraulic unit cannot

move any further upwards. It can however move down approximately .150 inches. This downward travel is the adjustment range. In other words, the adjustment length starts at 0.0 and can be as much as .150 inches. A correctly set adjustment positions the hydraulic unit in the middle of the .150 travel range. For hydraulic lifters to function correctly, the engine oiling system must operate with at least 10 to 15 psi oil pressure. Pressurized oil will then fill the area around the compression spring. And as far as hydraulic lifters are concerned, more oil pressure will not make the lifters run better.

Pushrod adjustments may now be completed. First, lengthen the

adjuster screw by hand until it makes tight contact with the

pushrod seat in the lifter. Then, extend the adjuster screw down

(making the pushrod longer) 3 or 4 full turns. (The exact number

of turns is not critical). Andrews Products adjuster screws for

EV80 and T88 pushrods are manufactured with (5/16 x 32)

threads so 3 turns will extend the pushrod length by .093 inches.

(3 x 1/32 = .093 inches). Each turn of the adjuster screw

changes the pushrod length by .032 inches.

The pushrod seat and hydraulic unit will now operate in a correct

position and will move up or down to compensate for engine

expansion due to warming up or cooling down of the engine. As

long as the hydraulic unit and pushrod seat can move up and

down and not touch the upper retaining ring or "bottom out" during

operation, the pushrod length has been correctly set and the

lifters will function normally.