Progressively wound valve springs. Which way up??

T

timtune

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After installing the first valve on the head of my '72 (ish) CB750 I realized that both inner and outer springs have two tighter coils on one end.
My feeble brain can't see that it should make any difference but I'm pretty sure it does. Which end should go up with the keepers.
 
I don't know the right answer. The answer that makes sense to me is doing what I can to minimize sprung weight so I would put the tight coils against the head and the wide coils against the keeper.
 
GreyGhost said:
I don't know the right answer. The answer that makes sense to me is doing what I can to minimize sprung weight so I would put the tight coils against the head and the wide coils against the keeper.
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That's the logic for fork springs. I don't know if there is similar logic for valves.
 
nobbie48 said:
That's the logic for fork springs. I don't know if there is similar logic for valves.
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The logic is sound as less oscillating mass means higher rpm before you float. My doubts come in as maybe something like the stacked coils provide more stability for the keeper is an overriding concern that I don't know about. @bitzz probably has the tried and true answer. I'm not sure if he has wandered away from gtam though.
 
Thanks All. I asked other places and they all say you are correct. Tight coils to the bottom means less weight to get moving.

GreyGhost said:
@bitzz probably has the tried and true answer. I'm not sure if he has wandered away from gtam though.
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Not so much wandered as shown the door. But yeah, he'd have known too.

nobbie48 said:
That's the logic for fork springs. I don't know if there is similar logic for valves.
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So in the forks the tight coils should be at the top since the forks are compressed upwards, correct?
 
Oops I forgot to paste and copies from the net. For the forks. Valves???

The more metal you shove into the oil, the higher the oil level will rise. So they recommend the tighter wound end face up to prevent raising the oil level too much above what it would be with the stock springs installed. Obviously, the spring doesn't care - it'll perform exactly the same whichever end goes in first.Oct 18, 2010
 
nobbie48 said:
Oops I forgot to paste and copies from the net. For the forks. Valves???

The more metal you shove into the oil, the higher the oil level will rise. So they recommend the tighter wound end face up to prevent raising the oil level too much above what it would be with the stock springs installed. Obviously, the spring doesn't care - it'll perform exactly the same whichever end goes in first.Oct 18, 2010
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The spring doesn't care which way is up but lower unsprung mass has no downsides. Thankfully, their oil reasoning and reduction in unsprung mass both align. I don't now if a mere mortal could feel the difference in unsprung mass in a fork. Valve springs at high rpm would be much easier to detect a difference in installation.
 
GreyGhost said:
The spring doesn't care which way is up but lower unsprung mass has no downsides. Thankfully, their oil reasoning and reduction in unsprung mass both align. I don't now if a mere mortal could feel the difference in unsprung mass in a fork. Valve springs at high rpm would be much easier to detect a difference in installation.
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IIRC the retainer clip for the wrist pin wants to know what direction is up and down.
 
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