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Valve Springs:

Are one of the most misunderstood and neglected items in an engine. It’s more than just a spring!!!

Valve springs on all factory Triples are a dual spring combination and are painted Red/White. The painted end usually goes to the bottom or cylinder head.

If using aftermarket springs make sure the end with the least amount of gap from the ground tail end base to the next coil up is placed to the bottom. Springs with a fat cut tail end resulting in a step to the next coil up can break or snap at that gap if placed down.

Aftermarket valve springs that have closely wound coils at one end only, must be placed with close wound coils down. The arrow in this picture is pointing at the top of the spring as an example so you can clearly see a large step where the coil finishes. If this was placed at the bottom in use it could snap at the coil above it

Valve springs can sometimes be out of square to the spring’s base. Meaning they lean in one direction more than the other when sitting on the bench. This out of square condition can have significant effect on wearing the valve guide rather quickly as the compressed spring tends to lean with pressure to one side rather than distributing the pressure evenly all around the base of the spring.

To check your springs, use a 6” engineers square placed on a flat surface and rest the spring standing correct end up against the square. Rotating the spring by hand one full turn will show any runout or out of square base condition. Springs with more than .090” runout or wobble should be avoided. This applies for the inner and outer spring. Do not attempt to grind square the base of a spring!

Always as mentioned make sure that either the inner or outer spring is fitted with the least amount of gap from the ground tail end of the base to the next coil up goes down, no matter if painted or not. This does not apply to close wound bottom coil springs or Beehive Springs.

Valve springs must have a nominated valve spring seat pressure to overcome several factors in aspirated engines. One is to resist from sucking the valve open as the piston on its downward stroke sucks in air/fuel mixture. The other is to maintain good valve seat sealing and heat transfer to the cylinder head.

Valves dissipate 75% of their heat to the head via the valve seat and 25% through the valve guide as a rule.

However, the main function of the valve spring is to control the valves opening and closing motions without losing the cam followers contact with the camshafts profile.

The valves weight itself places conditions on valve springs as the faster they open and close the heavier the valve becomes. An engine revving at 10,000rpm opens and closes the valve at 83.3 times per second.

That’s a hell of a lot of weight to control.

For standard engines changing the installed valve spring seat pressure to a higher spring pressure is not relevant as the factory nominated valve spring seat pressure is sufficient.

Adding spring shims under the spring to gain more spring pressure than the standard value is irrelevant and should be avoided as is fitting stronger and or thicker valve springs is also asking for trouble.

Factory installed valve spring seat pressure for a Triple is 85-90lbs @ 1.225” – 1.230”. All triples (Av I find is 82lbs) Full valve open spring pressure is 200-210lbs. For checking purposes mostly.

By changing the standard valve springs nominated installed and or full open pressure you are also changing its mechanical properties by altering its parameters of operation.

Valve springs have a certain poundage or pressure built into them for every .100” of travel required nominated by the spring manufacturer; therefore, introducing a stronger or longer valve spring unless prescribed by the cam manufacturer can be disastrous.

This could lead to insufficient spring travel remaining and become coil bound and or snap the wire due to increased heat generated in the spring wire itself. Yes, springs get hot just by moving! Real hot!

It’s like the coat hanger wire syndrome by quickly bending the wire backwards and forward in your fingers it eventually snaps and is bloody hot to hold.

However, if you are using lighter valves this will greatly reduce valve inertia and give the springs a helping hand of doing their job more efficiently. There is no real need or benefit to lighten rocker arms or pushrods or cam followers IMHO.

Using Alluminium or Titanium valve spring retainers has a significant benefit in reducing valve inertia considerably. Using those factory retainers, I see that are drilled with lightening holes is a waste of money.

You would be lucky to shed 3-4 grams whereas, Alloy or Ti retainers will shed 8-10 grams or more.

A factory Triple steel valve spring retainer weighs 15.8 – 16 grams and 2 collets weigh 2 grams. 

Take Note: One bad attribute associated with all valve springs is a demon called Valve Spring Harmonics.

Harmonics is a vibration or oscillation of the valve spring wire itself caused when the rocker arm or tappet strikes the tip of a valve at certain speeds sending shock waves down the wire of the spring. It is said that this shock wave can cause the valve spring to lift or jump from its seated position when running and consequently loses all relationship with the camshaft lobe and cam follower.

A noticeable effect of this occurrence is a feeling of the engine nosing over or losing power for several hundred rpm at around mid rev range, or around 3,800 to 4,200. It is not valve bounce or valve float, it is harmonics at its worst. 

Bounce and or Float for better words can happen at the extreme end of the rev range and can be controlled more easily by not revving that high in the first place or using a rev limiter device, whereas harmonics that I’m describing here occurs in the mid rev range and is a very serious phenomenon that mostly goes undetected.

And it is always related to the valve spring and nothing else!!! So only install the nominated springs at the nominated heights and pressures for your engine or modified engine according to the printed recommendations for the parts being used!!

Any harmonics introduced into the valve train by error or misunderstanding by introducing stronger, heavier or longer valve springs can and will have detrimental effects on this outcome.

Valve Train Harmonics can Kill Engines, Quickly!!

One quick and easy method to see if your valve springs have been subjected to harmonics is when you remove the valves spring retainer and collets. If for some reason it is difficult to separate and needs additional force to break the grip of the taper to get the collets out and if you see what I call the ‘checker flag’ syndrome or fretting on the back of the collets themselves and fretting under the valve spring retainer where the top of the valve spring rests against then this is telling you that you might have a problem. Normally a too soft a spring wouldn’t show any signs of fretting from harmonics so, therefore, it must be because of incorrect valve springs being fitted or an incorrect shorter installed height increasing the valve springs installed seat pressure.

This can quickly be rectified by replacing your springs with the correct springs according to your literature and or resetting the springs at the nominated valve spring installed height and poundage according to your literature or data supplied. 

Quality spring manufacturers always nominate a Spring Free Length, an Installed Seat Pressure and Height, an Open Spring Pressure Amount at Full Valve Lift plus a Coil Bind Dimension with a safety margin of say .060” to .080” associated with a particular camshaft and spring set for a given purpose. Unfortunately, most motorcycle manuals I’ve read don’t list this info so it’s a bit of a dark art and you have to ask or calculate this information yourself. Most manuals only give you the number of coils in a spring and a free length of that spring and a given seat and open pressure. The installed height information you need to know is never printed.

Why this measurement is never supplied is beyond me as it is the most important dimension you need when assembling and checking your valve train.

If using aftermarket cams and springs make sure you have their printed material, otherwise, ask for it. If they can’t supply any well-founded information/material avoid using their product as it would appear it’s just collected parts packaged from various suppliers and not a well thought out engine combination of selected proven parts by qualified specialists. Besides you do need to know this information.

Valves springs when produced go through several processes along with heat treating, grinding square and length check etc. plus one other process called ‘Scragging’.

The spring is subjected to multiple vertical compressions quickly striking down on the spring to coil bind for a fraction of a second to settle or ready a spring for use.

Unfortunately, Scragging doesn’t always work, plus some spring manufacturers use poor quality spring wire that just doesn’t make the grade.

So here is a method for you to try and check the quality and suitability for the springs you need to install.

1. Measure the free length of the outer valve spring in your hands with a Vernier Caliper and right it down, for example 1.605”.
2. Place that spring in a vice and wind the vice shut so that the spring reaches coil bind but, without any vice pressure on the spring. Just to touch.
3. Leave it there for 60 seconds only, then remove the spring and measure it once again at exactly the same position/place on the spring.

1. If it has shrunk or altered by more than .010” throw the springs away. This is telling you that those springs if fitted will only shrink or deteriorate more in a very short period of time in your engine resulting in a lessor valve spring seat pressure or open pressure than you originally required.

Realistically, the spring should still yield 1.600” to 1.605”.

Re-Scragging springs will not repair or return a spring back to the manufacturer’s specifications, admit defeat, they are stuffed and no good for any purpose.

Like anything else, there are springs and then there are springs, but now you know how the check them.

This is just one artricle from 170 pages of data i have written about our Triples. 

Bob (romac) Brackam.