Rocker shaft float or self centre?

[Hootlad]

This post is a bit long winded but read it through. If nothing else it's an interesting technical question.

I discovered this when doing some camshaft work on my 2005 ZG1000 and wondered if anyone could explain it.

While doing a camshaft replacement decided to confirm the oil flow to the camshaft journals before installing the new cams. With no cams installed in the head I cranked the engine to observe if each journal was receiving adequate oil flow. All journals and rocker arms were receiving excellent flow expect for cam journal number 10, the right most journal of the intake cam, which was receiving a very poor flow.

Thinking there may be a blockage I pulled the intake rocker shaft from the head, cleaned and inspected it, along with the intake rocker arms. Satisfied all was well, I re-installed the intake rocker shaft and rocker arms. When I reinstalled the rocker shaft I pushed it in as far as it would go (left) then re-installed the rocker shaft plug.

When I tested for oil flow again I noticed that the right most journal, number 10, the one that had the previous flow issue, was now receiving an excellent flow of oil. Great I thought, problem solved, until I took a look at journal 6, the left most intake cam journal. Where it did have an excellent flow of oil before it NOW HAD ZERO.

OK, so the rocker shaft is as far left as possible and it cuts off the oil to journal 5, the left most journal. So I remove the rocker shaft plug, grab my trusty calipers, and measure the depth from the rocker shaft end to the rocker shaft plug sealing surface. Next I measure the depth of the rocker shaft plug itself. What I find is the plug is short enough to leave about a 3mm space between itself and the rocker shaft. In other words the rocker shaft plug does not positively locate the rocker shaft but instead leaves about 3mm for the rocker shaft to float within the head.

So I pull the rocker shaft plug once again and by pulling the shaft out a bit, sort of half of the allowed free float, oil flow is restored to both journals 6 and 10. Just for kicks I pull the plug again and then pull the rocker shaft out far enough so that the rocker shaft plug, when reinstalled, will contact the rocker shaft during thus allowing the plug to butt-up against the rocker shaft and thereby remove all float clearance on the right side. As expected journal 10 now has zero flow.

In these engines the rocker shafts act as oil galleries for the cam journals and rocker arms but having it at either extreme of float cuts off oil supply to the respective cam journal.

Keep in mind the end cam journals are supplied by oil that flows from the ends of the rocker shaft and not by rocker shaft cross drillings as the other journals and rocker arms are.

Now obviously this Connie and many like her have clock hundreds of thousands of miles without seizing any camshafts but I'd like to know how.

I have a theory (perhaps "an assumption" would be a better word) that the rocker shaft is hydraulically centred by oil pressure working on the shaft ends when the engine is running. Being there is a relationship between flow and pressure, a higher flow from one end of the rocker shaft would result in a lower oil pressure acting on that end of the shaft, and visa-versa. Assuming the flow rate is directly related to float clearance at the respective shaft end (ie: less float clearance = reduced oil flow rate = increased oil pressure) would the rocker shaft move (float) left and right until it reached equilibrium?

Of course this self centring hydraulic action cannot be observed under the test conditions mentioned above. With the camshafts out and the engine only turning at cranking speed there are far to many holes and precious little flow in lubrication system to produce any oil pressure to speak of.

My question is am I right? Would some of you engine wizards like to chime-in on this and let me know. I can only assume the engineers at Kawasaki designed the engine like this for good reason and, like I said before, I have not heard of Connies seizing camshafts, so what gives?

I look forward to your replies,

Thanks,
Hoot.

 

[connie_rider]

Interesting question.
Without seeing a head/rockers I can't quite envision what you're talking about.
You may be right about it self-centering and lubricating all of the journals.
Thinking that it may also be a function of time/vibration that allows it to move and supply oil to all the journals at higher/sustained RPM's?

Luckily (with the valve cover on) the oil is being slung all over by rotating cams, moving rockers, etc.
This oil mist would help to prevent seizure too.

Ride safe, Ted

 

[ferabern143]

I think that the rotation of the assembly is not sufficient with the starter that the lubrication is the best and that the oil pump does not provide enough flows, in addition as the cover is removed the necessary pressure is not created in the engine.
In principle the oil centers the rotating elements after having a regular oil film on the peripheries, that is why a cold engine makes more mechanical noise, it is necessary that the oil goes well everywhere.

It is true that the intake camshaft is the farthest in the oil distribution, on my sidecar I mounted a ZZR1100 pump which brings 20% more flow, I also corrected some misalignments in the grease fitting.

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