"Milleer" tree wear test

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For years, the problem of the secondary transmission shaft has been discussed, so-called"Milleer", that over time accuses wear problems for friction with the pinion that mounts, up to conditions like those of the photo above.
In this article we mainly refer to the Honda Africa Twin and Transalp motorcycles, but the problem is also known to other motorcycles of other brands.

The replacement of a worn "Millerighe" involves a cost that makes it more economical, sometimes replace the engine with another newer. But over the years the chances of finding a newer engine go disappearing and you run the risk of finding a motor with a new tree but with worse problems.

Hypothesis 1

Many have tried into statements and hypotheses about the causes of this spreader, we also tried us, but with a more technical approach.

The hypothesis that the most believe plausible is that there is a strong difference in hardness between the materials of components in friction, and their superficial treatments: pinion and tree.
The results of the tests carried out on a single tree and a single pinion of a Honda XRV 750 Africa Twin.

Test feedback

For this reason we have brought an original sprocket into a specialist laboratory and a tree taken from a motorcycle to which replacement was required.

Both have been dissected according to the logic of points that come to friction, because they have a medium superior superficial treatment. Intermediate points were also measured, to have an overall idea of ​​the treatments made.

HR15NIt is a greatness of theRockwell scale. Who wants to know more about the type of tests carried out, can read the explanation ofWikipedia, while for those who want to have fun converting this measure to another that is more familiar, can do it using thisconverter.

These results:


HR15N Duresses Register

Overall: Pinone
Motorcycle Honda XRV 750 Africa Twin

The detail has been separated in order for the correct measurement of hardness in superficial and internal points of interest.


Section 1: measures not reported for detection problems


Section 2: Measures tooth hardness in socket on the grooved tree

1. 87
2. 85
3. 84


Section 3:Internal hardness measures (raw material)

1. 73
2. 71
3. 77
4. 78
5. 76
6. 74
7. 72
8. 78
9. 84 (lateral)



Section 4: Measure Hardness tooth chain side in socket during release

1. 87
2. 88


HR15N Duresses Register

Overall: grooved shaft for pinion cheaters (c.d. "Milleere")
Honda XRV 750 Africa Twin

The detail has been successful in order for the correct measurement of the hardness in the surface interest points of the face of the tree and its teeth into the socket.


Section 1: Surface hardness measures Face and grooved tree tooth

1. 92
2. 91
3. 90
4. 92
5. 84


Section 2: Surface hardness measures Face and grooved tree tooth

1. 87
2. 92
3. 92
4. 92
5. 85

Considerations on hypothesis 1

It is evident that our test shows its limits given the small number of measured samples. But, comparing us with other technicians who have already tried themselves in tests like these, we have reached the same conclusions.The harshness of the tree is greater than that of the pinion.This means that the hypothesis 1 is to decide, unless lots of lots have been produced, over the years, different suppliers that have used different types of treatments. But in the numerous feedbacks received by our customers, we were unable to go back to a coherence between this logic and reality. The statistics we have detected empirically related to abnormally worn trees are incompatible with this hypothesis and do not show concentrations, nor for models, nor for vintages, except for some vintage of some transalp models for which we have found a greater frequency than Defectivity. But this is a statement that we ourselves evaluate with the benefit of the inventory, given the type of investigations conducted.

Hypothesis 2

The conviction that the producer has deliberately created one is widespreadAxial and radial game between the pinion and the treeTo promote greater elasticity in the movement of the chain, especially for use in off-road.

Test feedback

We purchased in 2016 new trees and sprockets and we coupled them as requested. It seemed immediately evident, given the resistance opposite from the pinion grafting maneuver on the tree, which has also requested us the use of a bakelite trailer, which the game was not in the manufacturer's design will. Moreover, we also tried with a light point on the back, to verify that there were spaces due to tolerances. No light radius crossed the interstices between the shaft catching and the tooth of the pinion.

Although probing, we do not consider this exhaustive test because the spare parts we purchased are of the latest generations and may have suffered changes in the years of changes to try to remedy the problem. At the same time, this reiterates the will of the producer not to allow the game between the moving parts which, on the other hand, must turn solidly and without friction among them.

With this second test we believe we have missed another myth!

Other hypotheses and considerations

We consist that they can exist a set of concauses that can give rise, all together or only partially, to the anomaly object of our investigation. Between these:

  • Maintenance management does not comply with the required standards.
    Too often the simplicity that characterizes the maintenance of these means, leads to trying to try those who have no specific skills. These unknowingly end up causing damage of which they don't know how to give yourself an explanation. Some examples:
    - A chain draw too tight that induces the pinion to work eccentricly with respect to the tree and generates friction that, over time, begin to erode the superficial treatments of the contact parts.
    - The non-frequent replacement of the locking plate which, over time, is subject to the injuries of teeth wear that make an axial game to the pinion. This generates friction superior to the forecasts for which the hardening treatments have been realized.
    - We also include the lack of cleaning, sometimes only superficial, of the context in which the aforementioned components operate which, with the andar of the time, leads to the penetration of corpuscles between the parties in friction, generandon of larger.
  • Use of motorcycles for purposes higher than their real capabilities
    - Use of motorcycles in demanding off-road sessions, possible thanks to their performances, certainly does not make life easy to the parties involved.


Following our experiences, tests and considerations, we are brought to think that the abilities of these means have not been perfectly evaluated in the design phase. This made them famous because they went beyond the functional expectations for which they had been produced, but made some limits evident in the use of materials for the production of some components that, over the years, have proved fatal for users who They have come into possession of means already exploited above their real skills and / or have made them improper use themselves. This series of concuses, such as the main one, with the data available to us, is not given to us, have made sure that certain conceptual limits have become the Achilles heel.
We suffer this consideration by contrasting this hypothesis the awareness that other bikes, made with the specific intent of a much more intense and wearing use, despite everything, have resisted over time and have not presented novets abnormal prockons and trees.

All myths have their fantastic side and the real side.

If we look with a benevolent eye how many satisfactions have given to their owners, we cannot but exempt us from considering that these same exceptional performances, they have themselves generated the worst nightmares for those who have suffered the collapse of a dream that only a great passion can create.

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