The relationship between hydrogen and OP engines is therefore mutually beneficial: the 2-stroke OP architecture enables specific power outputs comparable to those of 4-stroke conventional gasoline engines, while hydrogen combustion allows the OP engine to operate with significantly reduced emissions [13]. Although this architecture has historically been used with conventional fuels such as gasoline or diesel, it is also suitable for alternative fuels beyond hydrogen, such as e-fuels and ammonia. However, using them in an OP engine may not provide a significant advantage as e-fuels are not carbon free and ammonia does not allow the use of ultra-lean combustion strategies due to its low flammability [14; 15; 16]. With the relevance of the aforementioned framework, this study aims to analyze the influence of different parameters on the crankshaft balancing of an OP engine. In the literature, several studies propose methodologies for assessing the balancing of various four-stroke engines. For example, [PERSON] et al. [17] and [PERSON] et al. [18] focus on developing an analytical model for the balancing of a traditional crankshaft. However, they do not consider OP architecture. [PERSON] et al. [19] investigate the dynamic behavior of an OP engine to evaluate its overall balance, but their study examines a configuration with a single crankshaft controlling both pistons. This latter configuration is fundamentally different from the one analyzed in the present paper, which addresses two separate crankshafts, each dedicated to its respective crank mechanism. For four-stroke engines, the main parameters influencing crankshaft balancing are generally the number of cylinders, the angle between crank throws, and the engine configuration (e.g., inline, V, or boxer). This article specifically examines the number of cylinders and the angle between crank throws, while the configuration is disregarded, as only inline OP engines are considered. However, when dealing with OP engines, additional parameters come into play. In particular, this study also takes into account a possible offset between the two crankshafts and their direction of rotation, which can be either co-rotating or counter-rotating. The present paper aims to establish an analytical methodology for evaluating the balancing of an OP engine by considering the four aforementioned parameters. It is important to emphasize that this study does not focus on any specific engine but instead provides a generalized framework, particularly useful in the early stages of the design process. The novelty of this study does not lie in the general balancing of internal combustion engines, as this topic has been extensively covered in the literature, but rather in the analysis of a specific architecture (OP engine), with a particular focus on the interaction between the two crankshafts and the influence of the offset angle. To the authors' best knowledge, no previous studies in the literature have specifically addressed this aspect, highlighting the gap that this research aims to fill. The paper is organized as follows. First, Section 2 \"Problem Description\" outlines the criteria used to evaluate crankshaft balancing and introduces the four key parameters considered in the analysis. Then, Section 3 \"Model Description\" presents the analytical model developed for this study. Next, Section 4 \"Results\" examines how each parameter influences engine balancing. Finally, the paper concludes with a summary of key findings and final remarks.