Exhaust emission mechanism for large displacement motorcycle engine
By designing an inclined exhaust labyrinth and complex channel structure in the crankcase of a motorcycle engine, the problem of oil injection in exhaust gas of large-displacement motorcycle engines has been solved, achieving efficient oil return and clean exhaust gas discharge, reducing lubricant loss and oil injection volume.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- 重庆浩森摩托车有限公司
- Filing Date
- 2025-08-27
- Publication Date
- 2026-06-02
AI Technical Summary
Large-displacement motorcycle engines spray oil during exhaust, leading to increased lubricating oil consumption and environmental pollution. Existing filter structures are prone to clogging and have high resistance, affecting exhaust efficiency.
The design employs an inclined exhaust labyrinth and serpentine/irregular channels, combined with air guide holes and oil return grooves, to form a complex exhaust gas emission channel. This allows the oil-gas mixture to flow in different directions, with engine oil adhering to the labyrinth baffles and flowing back into the crankshaft cavity. At the same time, ventilation baffles and oil guide plates are installed to prevent engine oil from entering the labyrinth, thus reducing the oil content in the exhaust gas.
It effectively reduces the oil content in exhaust gas, reduces lubricant consumption, avoids channel blockage, improves exhaust gas discharge efficiency, and reduces oil injection volume to 5ml/hour.
Smart Images
Figure CN224315055U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of motorcycle engines, specifically to an exhaust gas emission mechanism for a crankcase of a large-displacement motorcycle engine. Background Technology
[0002] Motorcycle engines include a crankcase, which comprises a left crankcase, a right crankcase, and a gasket positioned between the connecting ends of the left and right crankcases. During engine operation, exhaust gases produced in the combustion chamber enter the crankshaft cavity of the crankcase. These exhaust gases form a fuel-air mixture, which passes through an exhaust labyrinth within the crankcase and is then discharged through the exhaust port, resulting in exhaust gas fuel injection. Generally, small-displacement motorcycle engines have a smaller amount of fuel injected into the crankcase during exhaust gas injection; the larger the displacement, the larger the amount of fuel injected.
[0003] To address the issue of oil spraying from exhaust gas, Chinese Patent No. CN201090267Y discloses a crankcase exhaust gas circulation and oil filtration device. This device includes a right crankcase, a crankcase mat, and a left crankcase. The left crankcase has a vent pipe, and the crankcase mat has an exhaust port. The right crankcase also has an exhaust port, and a vent baffle is provided on the intake side of the exhaust port in the right crankcase. An exhaust channel is formed by the exhaust port, the exhaust labyrinth groove of the right crankcase, and the crankcase mat; the exhaust port of the crankcase mat; the exhaust labyrinth groove of the left crankcase; and the vent pipe. A filter screen is installed on the channel formed by the exhaust labyrinth groove of the right crankcase and the crankcase mat. The filter screen matches the exhaust labyrinth groove of the right crankcase, and the end face of the filter screen covers the exhaust port. With the above-described oil filtration structure, the filter screen and venting baffle can separate the oil and gas mixture, allowing the lubricating oil to return to the right crankcase, thus solving the oil injection problem, reducing environmental pollution caused by oil injection and lubricating oil consumption, and lowering operating costs. However, the oil-gas mixture contains impurities, and the filter screen is prone to clogging after prolonged use, affecting exhaust gas discharge. Furthermore, the filter screen increases air resistance as it passes through, further impacting exhaust gas discharge efficiency. Summary of the Invention
[0004] In view of the above-mentioned shortcomings of the existing technology, the purpose of this utility model is to provide an exhaust gas emission mechanism for the crankcase of a large displacement motorcycle engine, so as to solve the problem of exhaust gas injection in the existing exhaust gas emission structure.
[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0006] An exhaust gas emission mechanism for a crankcase of a large-displacement motorcycle engine includes a left crankcase, a right crankcase, and a crankcase gasket positioned between the connecting end faces of the left and right crankcases. An exhaust labyrinth B and an exhaust labyrinth A are respectively provided at the upper ends of the left and right crankcases. Both exhaust labyrinth B and exhaust labyrinth A are inclined in the same direction. An exhaust gas inlet is provided at the lower position of exhaust labyrinth A, and a serpentine exhaust channel is provided within exhaust labyrinth A. Exhaust labyrinth A and the crankcase gasket form a first exhaust channel. An irregularly shaped exhaust channel is provided within exhaust labyrinth B, and exhaust holes and oil return grooves are respectively provided on the upper and lower sides of the lower position of exhaust labyrinth B. Exhaust labyrinth B and the crankcase gasket together form a second exhaust channel. A guide hole for connecting the first and second exhaust channels is provided at the upper position of the crankcase gasket corresponding to exhaust labyrinth B and exhaust labyrinth A. The first exhaust channel, guide hole, second exhaust channel, and exhaust hole together form an exhaust gas emission channel. With the exhaust labyrinths in both the left and right crankcases tilted, exhaust gas enters exhaust labyrinth A from outside the crankshaft cavity via the exhaust gas inlet. After passing through the serpentine exhaust channel of exhaust labyrinth A, it enters exhaust labyrinth B through the air guide hole. After passing through the irregularly shaped exhaust channel of exhaust labyrinth B, the exhaust gas is discharged from the exhaust port. During the exhaust gas discharge process, because the exhaust gas inlet is at a low position, after the exhaust gas enters from the right crankcase, the air-fuel mixture rises from a low position to a high position, eventually entering the left crankcase. It then flows from a high position to a low position and is finally discharged through the exhaust port. During this process, the air-fuel mixture first travels through the serpentine exhaust channel, and the engine oil adheres to the labyrinth partitions within the channel before flowing back from a high position to a low position and being guided to the outside of the crankshaft cavity through the exhaust gas inlet. Simultaneously, after passing through the housing gasket and entering the exhaust labyrinth B of the left crankcase, the oil-air mixture flows from high to low. During this flow, the oil in the mixture adheres to the labyrinth partitions of the irregularly shaped exhaust channel, eventually depositing and dripping before flowing towards the lower oil return groove. This allows the lubricating oil to return to the crankshaft cavity, lubricating the components within. This structure allows the exhaust gas to pass through two exhaust channels sequentially, resulting in a longer exhaust path that effectively increases oil adhesion and return. Furthermore, after passing through the second exhaust channel, the gas direction changes from high to low within the exhaust labyrinth B before exiting through the upper exhaust port (exiting from the lower labyrinth to the higher exhaust port). The return oil flow direction is opposite, from high to low, preventing oil from being flushed towards the exhaust port. This significantly reduces the oil content in the exhaust gas and minimizes lubricant loss. This improvement in the exhaust and return oil paths not only reduces the oil content in the exhaust gas but also prevents blockages in the exhaust channels.
[0007] Furthermore, a venting baffle can be detachably installed at the intake end of the exhaust gas inlet and on the right crankcase. With the venting baffle installed at the intake end, it will block part of the space, preventing the lubricating oil in the clutch chamber from being thrown towards the exhaust gas inlet. This will prevent most of the thrown-up lubricating oil from directly entering the exhaust labyrinth A through the exhaust gas inlet.
[0008] Furthermore, a corresponding oil guide plate is provided at the lower end of the oil return groove, with the end of the oil guide plate inclined downwards. In this way, the oil guide plate can catch the returning lubricating oil after it drips in the oil return groove and guide the lubricating oil to the crankcase.
[0009] Furthermore, an excess oil guide hole is provided near the exhaust gas inlet on the crankcase gasket. In this way, when the oil-gas mixture is introduced from the exhaust gas inlet, the excess residual lubricating oil at the exhaust gas inlet will be guided through the excess oil guide hole to the corresponding position in the exhaust labyrinth B, where it will merge with the lubricating oil deposited in the oil return groove and finally enter the crankcase.
[0010] Furthermore, a T-shaped labyrinth partition and an L-shaped labyrinth partition are provided within the exhaust labyrinth A. The T-shaped labyrinth partition is positioned near the lower part of the labyrinth, with an air passage notch on its horizontal partition and an oil return notch at the lower end of its vertical partition. An air passage gap exists between the L-shaped labyrinth partition and the T-shaped labyrinth partition, and the L-shaped labyrinth partition is positioned near the higher part of the exhaust labyrinth A. Thus, the T-shaped and L-shaped labyrinth partitions, together with the inner wall of the exhaust labyrinth, form a radial exhaust channel. This allows the oil-gas mixture, upon entering, to first pass through the air passage notch, then be guided towards the L-shaped labyrinth partition, and finally through the gap between the L-shaped and T-shaped labyrinth partitions to the air guide hole of the gasket.
[0011] Furthermore, a reinforcing rib is provided next to the T-shaped labyrinth partition. This is because the presence of an air vent in the T-shaped labyrinth partition weakens the strength of the housing at that point. Therefore, adding a reinforcing rib effectively increases the strength of this area and extends the service life of the right crankcase.
[0012] Furthermore, a first inclined labyrinth partition is provided within the exhaust labyrinth B, extending along the length of the exhaust labyrinth B and dividing it into a first exhaust channel and a second exhaust channel. Two U-shaped notches are spaced apart on the first inclined labyrinth partition. A second inclined labyrinth partition is also provided at the upper end of the first exhaust channel within the exhaust labyrinth B, with an exhaust gas outlet located in the middle of the second inclined labyrinth partition. Thus, after entering the exhaust labyrinth B, the exhaust gas flows towards the exhaust port through the first and second exhaust channels, and finally passes through the second inclined labyrinth partition for oil-gas separation before being discharged, ensuring that the discharged exhaust gas contains only a very small amount of lubricating oil.
[0013] Furthermore, an integrally formed first baffle plate is provided at the upper end of the first inclined labyrinth baffle plate, between the two U-shaped notches. The depth of the first baffle plate is less than the depth of the exhaust labyrinth B. In this way, the first baffle plate can further enhance the oil-gas separation effect in the first exhaust passage, while its shallow depth will not affect the flow of exhaust gas.
[0014] Furthermore, the exhaust port and the oil return groove are staggered. This arrangement ensures that the exhaust path and the oil return path do not interfere with each other, and no air convection occurs between them. Attached Figure Description
[0015] Figure 1 This is a cross-sectional structural diagram of the crankcase of the motorcycle engine in the embodiment;
[0016] Figure 2 This is a schematic diagram of the disassembled structure of the right crankcase and the housing gasket in the embodiment;
[0017] Figure 3 This is a schematic diagram of the right crankcase in the embodiment;
[0018] Figure 4 This is a schematic diagram of the left crankcase in the embodiment. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this utility model provided in the accompanying drawings is not intended to limit the scope of the claimed utility model, but merely represents selected embodiments of the utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.
[0020] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0021] In existing crankcase designs, exhaust gases are mostly guided from the left crankcase to the right crankcase, ultimately exiting through the exhaust port on the right crankcase. Initially, the exhaust gases move from a high to a low position within the crankcase's labyrinth, then exit from a low to a high position. However, during this exit process, the oil drain hole is located at the lower end of the labyrinth, and the return oil direction is the same as the gas exit direction. This carries back the lubricating oil, resulting in oil spraying from the exhaust port. This is especially problematic for large-displacement motorcycle engines, where high RPMs can lead to nearly 100ml of oil being sprayed from the exhaust port within two hours of riding. Therefore, controlling the amount of oil sprayed from the exhaust gas of large-displacement motorcycles to reduce lubricating oil consumption is a pressing issue.
[0022] To address the aforementioned problems, this embodiment provides an exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine (such as...). Figures 1-4As shown), it includes a left crankcase 3, a right crankcase 1, and a housing gasket 2 placed between the connecting end faces of the left crankcase 3 and the right crankcase 1; an exhaust labyrinth B31 and an exhaust labyrinth A11 are respectively provided at the upper ends of the left crankcase 3 and the right crankcase 1; both the exhaust labyrinth B31 and the exhaust labyrinth A11 are inclined and in the same direction; an exhaust gas inlet 12 is provided at the lower position of the exhaust labyrinth A11, and a serpentine exhaust channel is provided inside the exhaust labyrinth A11, the exhaust labyrinth A11 and the housing gasket 2 forming a first exhaust channel; inside the exhaust labyrinth B31 An irregularly shaped exhaust channel is provided. Exhaust holes 34 and oil return grooves 35 are respectively located on the upper and lower sides of the lower part of the exhaust labyrinth B31. The exhaust holes 34 and oil return grooves 35 are staggered. The exhaust labyrinth B31, together with the housing gasket 2, forms a second exhaust channel. At the upper part of the housing gasket 2 corresponding to the exhaust labyrinth B31 and exhaust labyrinth A11, a guide hole 21 (the guide hole 21 is a strip-shaped hole) is provided to connect the first and second exhaust channels. The first exhaust channel, guide hole 21, second exhaust channel, and exhaust holes 34 together form an exhaust gas discharge channel. Thus, with the exhaust labyrinths in both the left crankcase 3 and the right crankcase 1 tilted, exhaust gas enters the exhaust labyrinth A11 from outside the crankshaft cavity of the crankcase via the exhaust gas inlet 12. After passing through the serpentine exhaust channel of exhaust labyrinth A11, it enters the exhaust labyrinth B31 via the guide hole 21, and after passing through the irregularly shaped exhaust channel of exhaust labyrinth B31, the exhaust gas is discharged from the exhaust hole 34. During the exhaust gas discharge process, because the exhaust gas inlet 12 is at a low position, after the exhaust gas enters from the right crankcase 1, the oil-air mixture rises from a low position to a high position, eventually entering the left crankcase 3. It then flows from a high position to a low position through the exhaust labyrinth B31, finally exiting through the upper exhaust port 34. During this process, the oil-air mixture first travels through a serpentine exhaust channel, with engine oil adhering to the labyrinth partitions within the channel, before flowing back from a high position to a low position and being guided to the outside of the crankshaft cavity through the exhaust gas inlet 12. Simultaneously, after passing through the casement gasket 2 and entering the exhaust labyrinth B31 of the left crankcase 3, the oil-air mixture flows from a high position to a low position. During this flow, the engine oil in the oil-air mixture adheres to the labyrinth partitions of the irregularly shaped exhaust channel, eventually depositing and dripping. This deposited lubricating oil is then collected and guided to the crankshaft cavity to lubricate the various components within the crankshaft cavity. The above structure allows the exhaust gas to pass through two exhaust channels sequentially, resulting in a long exhaust path that effectively increases oil adhesion and oil return. Furthermore, after passing through the second exhaust channel, the gas first moves from a low position to a high position in the exhaust labyrinth B, and then exits through the higher exhaust port (the final exhaust path is from low to high). The final exhaust direction is opposite to the oil return flow direction, thus preventing oil from being flushed towards exhaust port 34 by the gas. This significantly reduces the oil content in the exhaust gas and minimizes lubricant loss. This improvement in the exhaust and oil return paths not only reduces the oil content in the exhaust gas but also prevents blockages in the exhaust channels.
[0023] like Figure 3 As shown, a venting baffle 4 can be detachably installed on the intake end of the exhaust gas inlet 12 and on the right crankcase 1. The venting baffle 4 partially covers the space at the intake end of the exhaust gas inlet 12, and there is an intake port between it and the space at the intake end. Exhaust gas enters the intake end through this intake port and then enters the exhaust labyrinth A11 through the exhaust gas inlet 12. A horizontally arranged internally threaded post is provided at the intake end. The venting baffle 4 is fixed by a bolt passing through it and engaging with the threaded hole of the internal thread. In this way, after the venting baffle 4 is installed at the intake end, it will block part of the space, preventing the lubricating oil in the clutch chamber from being thrown towards the exhaust gas inlet 12, and can prevent most of the thrown lubricating oil from directly entering the exhaust labyrinth A11 through the exhaust gas inlet 12.
[0024] like Figure 4 As shown, a corresponding oil guide plate 36 is provided at the lower end of the oil return groove 35. The end of the oil guide plate 36 is inclined downward and located above the balance shaft mounting hole. In this way, the oil guide plate 36 can catch the lubricating oil that drips into the oil return groove 35 and guide the lubricating oil to the crankcase.
[0025] like Figure 2 As shown, a T-shaped labyrinth partition 13 and an L-shaped labyrinth partition 14 are provided inside the exhaust labyrinth A11. The T-shaped labyrinth partition 13 is located near the lower part of the labyrinth. An air passage notch 131 is provided on the horizontal partition of the T-shaped labyrinth partition 13, and an oil return notch 132 is provided at the lower end of the vertical partition of the T-shaped labyrinth partition 13. The L-shaped labyrinth partition 14 has an air passage gap with the T-shaped labyrinth partition 13, and the L-shaped labyrinth partition 14 is located near the higher part of the exhaust labyrinth A11. In this way, the T-shaped labyrinth partition 13 and the L-shaped labyrinth partition 14 together with the inner wall of the exhaust labyrinth form a radial exhaust channel, so that after the oil-gas mixture enters, it first passes through the air passage notch 131, then is guided towards the L-shaped labyrinth partition 14, and then through the gap between the L-shaped labyrinth partition 14 and the T-shaped labyrinth partition 13, and is guided to the air guide hole 21 of the sealing gasket 2.
[0026] Furthermore, a reinforcing rib 15 is provided next to the T-shaped labyrinth partition 13. In this way, after the air gap 131 is set at the T-shaped labyrinth partition 13, the strength of the housing at that point will be weakened. Therefore, by adding the reinforcing rib 15 next to it, the strength at that point can be effectively increased, thereby increasing the service life of the right crankcase 1.
[0027] like Figure 2As shown, an excess oil guide hole 22 is provided on the housing gasket 2 near the exhaust gas inlet 12. In this way, when the oil-gas mixture is introduced from the exhaust gas inlet 12, the excess residual lubricating oil at the exhaust gas inlet 12 will be guided through the excess oil guide hole 22 to the corresponding position of the exhaust labyrinth B, where it will merge with the lubricating oil deposited at the return oil groove 35 and finally enter the crankcase.
[0028] like Figure 4 As shown, a first inclined labyrinth partition 32 is provided within the exhaust labyrinth B31. The first inclined labyrinth partition 32 is arranged along the length of the exhaust labyrinth B31, dividing the exhaust labyrinth B31 into a first exhaust channel and a second exhaust channel. Two U-shaped notches 321 are spaced apart on the first inclined labyrinth partition 32. A second inclined labyrinth partition 33 is also provided at the upper end of the first exhaust channel and within the exhaust labyrinth B31, with an exhaust gas outlet 331 located in the middle of the second inclined labyrinth partition 33. In this way, after the exhaust gas enters the exhaust labyrinth B31, it flows towards the exhaust port 34 through the first and second exhaust channels, and finally passes through the second inclined labyrinth partition 33 for oil-gas separation before being discharged, so that the discharged exhaust gas contains only a very small amount of lubricating oil.
[0029] Furthermore, an integrally formed first baffle plate is provided at the upper end of the first inclined labyrinth baffle plate 32, between the two U-shaped notches 321. The depth of the first baffle plate is less than the depth of the exhaust labyrinth B31. In this way, the first baffle plate can further enhance the oil-gas separation effect in the first exhaust passage, and at the same time, its shallow depth will not affect the flow of exhaust gas.
[0030] After adopting the exhaust emission mechanism in this embodiment, the amount of lubricating oil collected after exhaust emission is greatly reduced to only 5ml when riding a motorcycle under the same road conditions and for the same amount of time.
[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of this utility model that do not depart from the spirit and scope of this technical solution should be covered within the scope of the claims of this utility model.
Claims
1. An exhaust gas emission mechanism for a crankcase of a large-displacement motorcycle engine, comprising a left crankcase, a right crankcase, and a crankcase gasket disposed between the connecting end faces of the left and right crankcases; an exhaust labyrinth B and an exhaust labyrinth A are respectively provided at the upper ends of the left and right crankcases; characterized in that, Both exhaust labyrinth B and exhaust labyrinth A are inclined in the same direction. An exhaust gas inlet is located at the lower position of exhaust labyrinth A, and a serpentine exhaust channel is located within exhaust labyrinth A. Exhaust labyrinth A, together with the sealing gasket, forms the first exhaust channel. An irregularly shaped exhaust channel is located within exhaust labyrinth B, and exhaust holes and oil return grooves are located on the upper and lower sides of the lower position of exhaust labyrinth B, respectively. Exhaust labyrinth B, together with the sealing gasket, forms the second exhaust channel. At the higher position of the sealing gasket corresponding to exhaust labyrinth B and exhaust labyrinth A, a guide hole is provided to connect the first and second exhaust channels. The first exhaust channel, guide hole, second exhaust channel, and exhaust hole together form the exhaust gas emission channel.
2. The exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine according to claim 1, characterized in that, A ventilation baffle can also be detachably installed on the intake end of the exhaust gas inlet and on the right crankcase.
3. The exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine according to claim 1 or 2, characterized in that, An oil guide plate is provided at the lower end of the oil return groove, and the end of the oil guide plate is inclined downward.
4. The exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine according to claim 3, characterized in that, The exhaust labyrinth A is provided with a T-shaped labyrinth partition and an L-shaped labyrinth partition. The T-shaped labyrinth partition is located near the lower part of the labyrinth. An air passage gap is provided on the horizontal partition of the T-shaped labyrinth partition, and an oil return gap is provided at the lower end of the vertical partition of the T-shaped labyrinth partition. There is an air passage gap between the L-shaped labyrinth partition and the T-shaped labyrinth partition, and the L-shaped labyrinth partition is located near the higher part of the exhaust labyrinth A.
5. The exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine according to claim 4, characterized in that, A reinforcing rib is also installed next to the T-shaped maze partition.
6. The exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine according to claim 4 or 5, characterized in that, An excess oil guide hole is provided on the gasket near the exhaust gas inlet.
7. The exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine according to claim 1, 2, 4, or 5, characterized in that, A first inclined labyrinth partition is provided inside the exhaust labyrinth B. The first inclined labyrinth partition is arranged along the length direction of the exhaust labyrinth B, dividing the exhaust labyrinth B into a first exhaust channel and a second exhaust channel. Two U-shaped notches are provided at intervals on the first inclined labyrinth partition. A second inclined labyrinth partition is also provided at the upper end of the first exhaust channel and inside the exhaust labyrinth B. An exhaust gas outlet is provided in the middle of the second inclined labyrinth partition.
8. The exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine according to claim 7, characterized in that, At the upper end of the first inclined labyrinth partition, between the two U-shaped notches, there is also an integrally formed first baffle plate, the depth of which is less than the depth of the exhaust labyrinth B.
9. The exhaust gas emission mechanism for the crankcase of a large-displacement motorcycle engine according to claim 8, characterized in that, The exhaust port and the oil return groove are misaligned.