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2019 Kawasaki New Valve Train

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I was looking into the changes for the 2019 Kx450f and one of the biggest changes was the head and valve train design.

It uses finger followers to actuate the valves acting as an intermediate point between the cams and the valves.

I wanted to post this here to hopefully get some feedback from engine and mechanical people who may know more about this design.

Do you think it is an outright improvement over the other valve designs?

How would you go about keeping valve clearances in spec with such a design? Would that be different since they say there are no buckets or shims?

Should it make the valve train any more or less reliable?

I don't know a lot about the detailed mechanics of a 4 stroke, but I find tech stuff interesting, so just looking for information really.

In this video they give a good demo of some changes around the 3 minute mark.

 

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Each valve is adjusted individually. If they do not use a shim/bucket and they use an intermediate 'rocker arm, either the rocker arm has an adjustable pivot (most likely in this case) or there is an adjuster on the end that presses on the valve stem. The advantages of this system is the ability to provide a ratio between the cams lift (possibly providing a smoother cam ramp in the process) and the lift provided at the valve and not have the cams interfering with spark plug placement. The disadvantages are more reciprocating mass,  Increased engine height, greater complexity and more difficult to adjust. A shim in bucket just uses math and only goes out of adjustment from valve wear, the mechanism (cams, buckets and shims) do not wear. Finger systems have massive pressures when the finger presses the valve and often 'dent' making accurate measurement at the valve stem impossible.

IMHO, it is a change to make it 'all new for 2019' and I doubt there is any performance to be gained. F1 and most high end race engines are all shim in buckets. Simple, durable, lightweight.

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20 minutes ago, William1 said:

The disadvantages are more reciprocating mass,  Increased engine height, greater complexity and more difficult to adjust. A shim in bucket just uses math and only goes out of adjustment from valve wear, the mechanism (cams, buckets and shims) do not wear. Finger systems have massive pressures when the finger presses the valve and often 'dent' making accurate measurement at the valve stem impossible.

The denting effect of the valve is something to think about. I wonder if that would come into play much sooner than the intended service life of the valve? Or if there is a piece that would be a replaceable point of contact?

I was thinking that while the finger followers allowed steeper cam angles to in turn create a greater lever movement, that would also mean a smaller amount of wear would make a larger difference of the output as well? Could it be that this setup might be more sensitive to wear?

Function wise it seems like a good idea, especially the part about eliminating side loads on the buckets.

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17 minutes ago, Catbatman said:

The denting effect of the valve is something to think about. I wonder if that would come into play much sooner than the intended service life of the valve? Or if there is a piece that would be a replaceable point of contact?

I was thinking that while the finger followers allowed steeper cam angles to in turn create a greater lever movement, that would also mean a smaller amount of wear would make a larger difference of the output as well? Could it be that this setup might be more sensitive to wear?

Function wise it seems like a good idea, especially the part about eliminating side loads on the buckets.

Denting starts the second it is started the first time. If clearances are measured at the cam and not the valve, it would be inconsequential on a race engine. You'd be giving it a full rebuild well before it was a serious problem. If measured at the valve, you's alsway have loose vlaves, possibly hiding valve head recession, not a good thing at all.

If there is any ratio on the fingers, lift would be resolved though cam diameter. simply put, lets say it was a 2 to 1 ratio.  Normally, the design would have a 1/2" lift on a 1.5 inch base diameter, making the base to lobe tip 2". You use a finger with 2/1 ratio. Your cam could now be a 3" base with a 1" life, now measuring 4" base to tip. The larger diameter cam has gentler radius and this is a less violent design. but, you have a lot more reciprocating mass and a lot of large parts to contain.

If the adjuster is a eccentric screw pivot, that cam move the finger position, in some designs, this results in excessive finger or cam wear. The best designs of this type use a keyed eccentric insert, swapping inserts to change clearance. But you are back to have a box of inserts and doing the math as you would with shim in buckets.

For fingers to make sense, there has to be a good reason such as valve angle or spacing. I was always amazed Yamaha got away with out using fingers on the five valve engines, though they did tend to 'eat' center valves first.

The side loading of buckets is inconsequential.

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The valve train will be more durable.  This is a properly designed valvetrain for a high RPM engine.  .  

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Posted (edited)

Honda four cylinder engines used the finger follower with the adjustment on the end of the finger. Soooo easy to adjust. I love them. 

Edited by LukeYZ426F
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16 hours ago, LukeYZ426F said:

Honda four cylinder engines used the finger follower with the adjustment on the end of the finger. Soooo easy to adjust. I love them. 

Makes we wonder how they will go about doing the adjustments on this kx450. It does sound like an easier process if adjusters or inserts like that are used.

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As far as the denting goes, wouldn't a full roller set up like they use in some automotive applications resolve the denting issue? Some automotive applications use roller rocker arms that have a roller on the pivot and a roller on the valve end of the rocker. The roller obviously reduces friction and in theory should prevent any major denting since it will have more surface to disperse its pressure across. 

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