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Originally Posted by Dan  I am doing a build with a Honda GX50. Could some one suggest a proper ratio. I tried the calculator (Thanks Ocscully) and found out my 50cc MB will go 4,054 MPH. It seems I am a bit lost.
I am looking at this jack shaft set to just try and figure this out; "Includes shaft, 10 tooth sprocket, 14 tooth sprocket, 2 bearing hangers, 2 standard bearings, 2 keys and collar"
I keep losing the concept after 2 sprockets. So please typ slow,
I was trying to avoid a gear box, but this ain't lookin good. |
Lets take our target to be 18.75:1 total reduction. I think you can get a clutch for your honda GXH50 with a 12t output so you input 12 into the first field of the calculator. then you want to get at least 3:1 to your jackshaft maybe even 4:1 so for 3:1 you would input 36 and for 4:1 input 48 into the second field. then you would have another 12t driver on your jackshaft so input 12 into the third field then your final driven sprocket at the wheel lets say a 56t so input 56 into the forth field.
so when you input the 36 for 3:1 to the jackshaft you end up with a total reduction of 14:1 (not enough) but this set up would give you a max speed of 39.8mph @ 7200rpm but you would burn up the clutch in very short order on the starts. With the 48t 4:1 to the jackshaft you end up with a total reduction of 18.67:1 (target 18.75:1) max speed 29.8mph @ 7200rpm.
To get to the target total reduction with the 36t 3:1 to the jackshaft you would need a 75t final driven sprocket at the rear wheel.
So with the calculator you can play with the various sprocket combinations and see your speeds at any given rpm. Buy inputing your idle rpm plus approx 300-500 rpm you can see how fast you need to get the bike going to save the wear and tear on your clutch.
ocscully
