Valve Adjustment, Intake vs Exhaust

I just want to make sure I'm doing this correct before I get too far. On my 1982 GPZ750, I'm doing a valve adjustment. The manual tells me to measure the clearances for two INTAKE valves on timing mark "1 4", either cylinders "#1 and #3, or #2 and #4".

This confuses me, because on timing mark "1 4", I have intake valve #1 completely closed, but intake valve #3 is completely open. (edit: valves #2 and #4 are closed, the lobes pointing to sideways, are those the valves to be measured?) Should I be measuring an open valve? I thought that clearances were checked where the both corresponding valves are closed.

A better question for a newbie, should the cam lobe be pointing up, down, or to the side for when I'm measuring?

Thank you!

If you do it the way the manual says you have to turn the motor to 4 different positions to measure them all. (I think 4 positions is right) Most people just turn the camshaft until the lobe of the cam is pointed directly away from the valve they want to measure clearance on. When I did mine recently I found I got two different sets of measurements, one when doing it the way the manual states, and one when doing it the other easier way. But the measurements were so close on each method I did that they were basically the same as far as selecting new shim sizes was concerned.

74ullc wrote: If you do it the way the manual says you have to turn the motor to 4 different positions to measure them all. (I think 4 positions is right) Most people just turn the camshaft until the lobe of the cam is pointed directly away from the valve they want to measure clearance on. When I did mine recently I found I got two different sets of measurements, one when doing it the way the manual states, and one when doing it the other easier way. But the measurements were so close on each method I did that they were basically the same as far as selecting new shim sizes was concerned.

I've noticed the same thing.

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Good to know, thank you.

On all four of my intake valves I have zero clearance, but I'm just going off the manual and hope to get my compression back.

Yup....definitely need to get the correct clearance on those valves back! Zero = no good.

Consider this.... The only time a valve is open is when the cam lobe is pressing on the bucket, shim, & valve stem. That is what holds the valve open. So if you try to measure the clearance at that position the clearance will always be zero. If you measure the clearance when the cam lobe is pointing as shown in the manual or pointing directly away from the valve there should be a gap between the cam and the bucket (or shim if your bike has shim over bucket). So that is when you can measure the clearance. Ed

Just measure with the lobe pointing 180 deg away from the valve.
This is the best way and makes sure you are taking the measurement on the base circle and well away from the ramp.