Simple valve adjustment - jpaige method

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Simple valve adjustment - jpaige method

Postby Doc » June 9th, 2008, 9:11 am

This method was developed by jpaige, and is based upon the thread pitch of the tappet screw to determine the gap.

If you do the math, you convert the pitch of the screw into degrees of rotation.

.75mm pitch = .02952756" per revolution = .000082" per degree
intake .003" to .005" = 36-60 degrees (call it 45)
exhaust .007" to .009" = 85-109 degrees (call it 90)

Sooo, to achieve the clearance for the intake valve, loosen the lock nut, screw the tappet down until it touches the top of the valve, and then back it off 45 degrees (1/8 turn) Same thing for the exhaust, back off 90 degrees (1/4 turn)

-- Edit for additional notes and a couple of tips and tricks..

To make sure you are at top dead center on any particular head, after turning the engine to the marked spot, grab the Y shaped bracket between the valve adjustment screws and lift up and down. The movement should be very very slight. If you feel a bunch of movement, or no movement at all, turn the engine until you hit the line again and re-check. Another sure fire method is to place a wooden dowel in the spark plug hole. Rotate the engine to the marked line and you will be able to visibly see when the plug is top dead center.

When making adjustments using the above method, first unlock and unscrew several turns BOTH adjustment screws. Then only screw down and back off the suggested amount above on one screw at a time. This ensures one screw does not throw the other out of spec.

See this file for details on dis-assembly and setting top dead center for the heads.


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