'77 valve springs question

I just got the new SS Kimblewhite valves all lapped in and back together and heard on a different forum that some valve springs have a specific orientation as far as which side is up and which is down. Do the KZ'z have this?

I just read in the Clymer's that 'some' bikes have variable rate springs, but it doesn't say which bikes have them. Does mine?

what cams and what springs are you running?

stock

kzmason wrote:

I just got the new SS Kimblewhite valves all lapped in and back together and heard on a different forum that some valve springs have a specific orientation as far as which side is up and which is down. Do the KZ'z have this?

The 750 twins do NOT because I have a factory manual and they don't address that at all. They do have a whole lot of text devoted to the valve springs and how to measure their strength.

I have no idea how or why a spring would have an up/down unless it was a different diameter at one end.

bountyhunter wrote:

I have no idea how or why a spring would have an up/down unless it was a different diameter at one end.

Variable pitch/rate springs have the spring coils wound closer at one end - these springs should be installed with the closely wound end facing towards the head.

Can´t tell you which KZs have them and which don´t, but they´re fairly easy to spot, if you can´t see one end being wound closer than the other don´t worry about it.

Post edited by: OnkelB, at: 2008/01/28 14:53

OnkelB wrote:

bountyhunter wrote:

I have no idea how or why a spring would have an up/down unless it was a different diameter at one end.

Variable pitch/rate springs have the spring coils wound closer at one end - these springs should be installed with the closely wound end facing towards the head.

Can´t tell you which KZs have them and which don´t, but they´re fairly easy to spot, if you can´t see one end being wound closer than the other don´t worry about it.<br><br>Post edited by: OnkelB, at: 2008/01/28 14:53

I just wasn't seeing why a variable would have an up down: the head surface is flat, the big washer at the top is flat. I'm not sure how I see the spring would know which end it was facing? It's still being squeezed the same.

We use variable rate springs in guns all the time and they don't have a polarity.

Post edited by: bountyhunter, at: 2008/01/28 16:32

That is why the spring coils are closer wound at one end. Perhaps there is a difference between guns and motorcyle engines ??

Bounty, you may be right, I´m not really an authority on the subject, but both my 650 and my 1100 manual have specific notes about installing variable rate springs that way.

I think it has something to do with the variable rate springs having close to stock seat pressure and initial opening pressure, then as the valve opens more and the spring compresses it gets progressively tighter to prevent valve float at high rpms. Anyone?

Post edited by: OnkelB, at: 2008/01/28 17:37

OnkelB wrote:

Bounty, you may be right, I´m not really an authority on the subject, but both my 650 and my 1100 manual have specific notes about installing variable rate springs that way.

I think it has something to do with the variable rate springs having close to stock seat pressure and initial opening pressure, then as the valve opens more and the spring compresses it gets progressively tighter to prevent valve float at high rpms. Anyone?<br><br>Post edited by: OnkelB, at: 2008/01/28 17:37

I get you as to why a progressive spring would be an advantage, I am just not getting how a spring would know if it was installed upside down unless the ends are specifically different by design to mate up with a retaining collar or some such thing. If both ends mate with a flat surface, the spring won't know the difference as it is compressed.

The ends must be different if they have an up and down.

The only other reason might be they want the end with more coils near the head to get more heat to flow out of the spring and into the head? Beats me.

Post edited by: bountyhunter, at: 2008/01/28 19:55

hwms wrote:

That is why the spring coils are closer wound at one end. Perhaps there is a difference between guns and motorcyle engines ??

The reason behind variables is the same in guns: you want a softer spring at the initial compression stage to allow easier unlock which reduces the first recoil impulse height, but you want the spring to get exponentially stronger as the slide nears the frame so it won't slam into it.

For valves you want the increase to stop the valve from floating or beating the top off the seal.

Post edited by: bountyhunter, at: 2008/01/28 19:58

As the valve reaches it extreme limit of downward travel and begins to reverse direction of travel there is a very minute hesitation to move. By having the lower end of the valve spring coils wound closer together tends to cause initial force on the valve to be greater thereby causing the valve to begin closing more rapidly and causes the valve follower to stay in contact with the cam lobe until the valve reaches the upper limit of travel. This results in a more efficient valve train operation. Once the valve is in an upward motion the less tightly wound coils are sufficient to maintain contact. This also prevents hammering of the valve follower by the cam lobe when the valve is fully open.