Hurky
Husqvarna
AA Class
Hi there,
I am rebuilding my Honda CR250 2002 engine and I changed all the bearings except the one needle bearing and the sealed one you can see in the lower portion of the pic, those are from the shift drum and as they do not receive full rotations nor much stress I decided to not change them.
The reason for this thread is that I would like to understand why that lower bearing is sealed on one side and not just open as the remaining ones.
The oil level would be sitting approximately where the yellow line is
There are three main openings in the right hand cases that communicate between the clutch and transmission sides;
1 where the kick starter sits,
2 above the clutch with some funnel design that looks like it will be splashing oil inside the transmission side,
3 at the lower part probably to allow the oil to return to the clutch side and/or stabilize the level between both sides, overall there is only one fill port on the clutch cover...
So, why is that lower bearing sealed then ? I have several theories:
1: Maybe an low oil emergency situation ? When the oil is low, that 'pumping' mechanism of the clutch basked and that funnel design ensures that oil is splashing inside the transmission so the engine can continue to work for longer and not have an DNF race.
2: To avoid too much oil flowing back to the clutch side too fast ?
3: To reduce contaminants from one side to reach the other side easily ? This does not make too much sense as other parts are open and contaminants suspended in the oil will reach other parts in either case I would think.
As a side note, I noticed the same design on other brands such as the Suzuki RM250 etc where both that lower drum bearing is sealed as well as the main clutch bearing, this is also true for the previous 2001 year CR250's.
The reason I want to understand this is I am also building an CR500 engine from scratch and already got an open bearing for that one and I want to know the implications of running an open one vs a sealed. On the CR500 it is just a shielded bearing so not even providing a real seal.
Thanks for reading and cheers !
I am rebuilding my Honda CR250 2002 engine and I changed all the bearings except the one needle bearing and the sealed one you can see in the lower portion of the pic, those are from the shift drum and as they do not receive full rotations nor much stress I decided to not change them.
The reason for this thread is that I would like to understand why that lower bearing is sealed on one side and not just open as the remaining ones.
The oil level would be sitting approximately where the yellow line is
There are three main openings in the right hand cases that communicate between the clutch and transmission sides;
1 where the kick starter sits,
2 above the clutch with some funnel design that looks like it will be splashing oil inside the transmission side,
3 at the lower part probably to allow the oil to return to the clutch side and/or stabilize the level between both sides, overall there is only one fill port on the clutch cover...
So, why is that lower bearing sealed then ? I have several theories:
1: Maybe an low oil emergency situation ? When the oil is low, that 'pumping' mechanism of the clutch basked and that funnel design ensures that oil is splashing inside the transmission so the engine can continue to work for longer and not have an DNF race.
2: To avoid too much oil flowing back to the clutch side too fast ?
3: To reduce contaminants from one side to reach the other side easily ? This does not make too much sense as other parts are open and contaminants suspended in the oil will reach other parts in either case I would think.
As a side note, I noticed the same design on other brands such as the Suzuki RM250 etc where both that lower drum bearing is sealed as well as the main clutch bearing, this is also true for the previous 2001 year CR250's.
The reason I want to understand this is I am also building an CR500 engine from scratch and already got an open bearing for that one and I want to know the implications of running an open one vs a sealed. On the CR500 it is just a shielded bearing so not even providing a real seal.
Thanks for reading and cheers !
