To create this article, or at least part of it, I took inspiration from a question posed some time ago by an enthusiast who wondered whether it really took two mechanics three days to assemble the engine of a MotoGP, as he had read somewhere. Not much is known about the MotoGP, especially with regards to the mechanics and construction details. The construction schemes and the solutions adopted are known, but only in broad terms and certainly not in detail.
The manufacturers, in fact, provide nothing more than very vague data regarding the technique of their Grand Prix engines.
Non-standardized solutions | Garage
MotoGP engines, what we know and what we don’t
We know the same characteristic measurements thanks to the regulation and not because they are provided by the manufacturers. So we don’t know, for example, how long the connecting rods are. We have an approximate idea of the diameters of the main and connecting rod journals, while things are better for the measurements of the valves, given that we know the bore. When the Formula 1 World Championship was raced with 3000 cm³ naturally aspirated V10s and then with 2400 cm³ V8s, BMW communicated a series of interesting information including that relating to the time necessary for assembling an engine, made up of approximately 5000 pieces (including the connecting parts).
Three mechanics took three days. The engine of a MotoGP only has four cylinders and therefore the time required should be less, but on the other hand it must be considered that it also includes the gearbox, the clutch and the primary transmission (unlike what happens in the car field).
Therefore, it is plausible that it would take two mechanics two days to assemble. Three seems a bit much… At this point you may wonder why, given that for similar engines intended for road sports the time taken is much less. The fact is that in racing motorcycles everything is really “pulled” to the limit and even the smallest details must be treated with extreme attention: extraordinary precision is essential. The tolerances are much narrower than those used in series engines and the couplings are more critical.
In normal production the real compression ratio can vary quite a bit compared to the nominal, i.e. reference, one (and differ from cylinder to cylinder). For example, for its four-cylinder sports cars, until a few years ago, Suzuki indicated that a deviation of plus or minus 0.3 compared to the nominal value was possible.. In racing engines, the difference between the various cylinders regarding this ratio must be so small as to be practically zero. That is, it must be the same as possible for everyone. In engines intended for top-level competitions, the capacity of the combustion chambers is often not measured by introducing oil through the spark plug hole. Let’s be clear, the system is valid, but if you are looking for the best you need an even more accurate one! The weight of the pistons must be the same for all cylinders, with deviations contained within less than one gram.
The components must be selected with extreme care, ensuring that the sum of the tolerances is favorable. For example, tolerances come into play for the exact position of the piston at top dead center (TDC). relating to the length of the connecting rods, the compression height of the pistons and the shape of their crown. The compression ratio depends on anything that can affect the capacity of the combustion chambers.
Inevitably, not all connecting rods have exactly the same head-to-foot distance, but they present a very small deviation compared to the nominal value, and the same applies to the distance between the axis of the gudgeon pin and the edge of the piston crown, for the distance between the lower and upper planes of the cylinder and so on. This deviation constitutes the dimensional tolerance (as regards the measurement in question, i.e. the wheelbase). Naturally there are others, which concern all the measurements of the component, as well as its shape.
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