Water cooled motobike

Local time
3:38 AM
Joined
Oct 13, 2019
Messages
32
Location
Big Island
I don't use a jack-shaft. Mine is an 18.75:1 gearbox {15\44 drive} [28,36,44(34-13)]


Dang buddy it's a nice bike nice you can pull so much weight but man, you got alot going on there! For me the number one thing was a successful water cooled bike I know there are aren't alot of those around and wanted to make something all my own. I like it's got minimal (so to say) going on for what it is. Really just want to lower my overall current gear ratio so I have a bit more power in second going up hills. I'm not sure how to change the sprocket in this engine I pulled the clutch bell off and it seems like the sprocket is pressed into the bearing in the clutch housing I don't see any threads on it. I do have a pgn bearings I could press into the clutch housing I would need to go to a machine shop to get that done and a new engine sprocket pressed into the bearing 😐 not ideal
 

Sidewinder Jerry

Well-Known Member
Local time
8:38 AM
Joined
Mar 14, 2011
Messages
3,921
Location
Rockwood, TN
Dang buddy it's a nice bike nice you can pull so much weight but man, you got alot going on there! For me the number one thing was a successful water cooled bike I know there are aren't alot of those around and wanted to make something all my own. I like it's got minimal (so to say) going on for what it is. Really just want to lower my overall current gear ratio so I have a bit more power in second going up hills. I'm not sure how to change the sprocket in this engine I pulled the clutch bell off and it seems like the sprocket is pressed into the bearing in the clutch housing I don't see any threads on it. I do have a pgn bearings I could press into the clutch housing I would need to go to a machine shop to get that done and a new engine sprocket pressed into the bearing 😐 not ideal
Here's Fabian's duel chain-ring SBP shift kit. This'll help you get even lower ratios.



 

Sidewinder Jerry

Well-Known Member
Local time
8:38 AM
Joined
Mar 14, 2011
Messages
3,921
Location
Rockwood, TN
I put color coding on my shifters and can do all shifting with my left hand. I use a triple chainring shift kit. The only time a front chainring is shifted is when either in rear sprockets (3) or (5). Notice how the chain is always in a fairly straight line. Only the slightest of cross chaining.

20210704_204950.jpg

IMG_20220824_132527.jpg
 
Local time
3:38 AM
Joined
Oct 13, 2019
Messages
32
Location
Big Island
Nice graphic well done ok I see what I need to get to that next level. And maybe some performance mods, the actual polini engine this replica is made after is 6.5hp, and they make mods for that engine up to near 10hp so this engine has alot of power:weight. Lots of potential here. I didn't mention, the engine uses a 25h pocket bike chain so the 8t engine sprocket connected to the 47t gear connected to the jackshaft are 25h. A little detail I left out that might be affecting my ratio?
 

Chainlube

Well-Known Member
Local time
5:38 AM
Joined
Jan 5, 2020
Messages
6,989
Nice graphic well done ok I see what I need to get to that next level. And maybe some performance mods, the actual polini engine this replica is made after is 6.5hp, and they make mods for that engine up to near 10hp so this engine has alot of power:weight. Lots of potential here. I didn't mention, the engine uses a 25h pocket bike chain so the 8t engine sprocket connected to the 47t gear connected to the jackshaft are 25h. A little detail I left out that might be affecting my ratio?
You explained all that in post #1.
 
Top