Gearbox Ratios

[Barnesd09]

Here is the final finished product for you to play with and use as you please.
Speeds are only an indication and does not take into account the tyre deformation under load or the knobby's digging into the dirt.
Cells containing all the data are hidden and can be unhidden for you to view if you wish.

Enjoy.:beerchug:
View attachment gearing calc.xls

 

[Cactus Jack]

Planet Minis had a thread with gear ratios plus other info ... but it never got completed ...

Import Motor FAQ - Long Stroke Mills - Planet Minis

I've got a new Lifan 140 tranny so I'll pull that out later and count the teeth on each gear for ya' ... CBF'd ATM ... I've gotta get out and mow the lawn ...

Jialing GPX
Gear Ratios
1st: 3.181
2nd: 1.705
3rd: 1.238
4th: 0.958

Lifan 124 (Clutch on crank motors 54 x 54 b/s + 20 mm output shaft)
Gear Ratios:
1st 2.833:1
2nd 1.706:1
3rd 1.238:1
4th 0.958:1

 

[Cactus Jack]

18/67 does = 3.722 ...

The ONLY way to be 100% sure of a ratio is to count the actual teeth on the gears ...

Primary drive ratio = # of teeth on the clutch basket gear divided by the # of teeth on the crank gear ...

An engine with a 2.62 primary drive ratio would have to have a bigger crank gear and a smaller clutch basket gear than a 3.72 ratio primary drive such as Lifan 120/150/150 etc ...

 

[Cactus Jack]

Lifan 140 counting the actual teeth ...

Gear ratio :

1st gear = 11/35 = 3.181 to 1
2nd gear = 17/29 = 1.705 to 1
3rd gear = 21/26 = 1.238 to 1
4th gear = 24/22 = .916 to 1

 

[The_GDFP]

Save you a little math, for some of the Japan combo's. Ego-maniacal Monkey SpankZ site, but the calculator is useful.

Honda50.com Gear Ratio - Speed Calculator

YX160 18/67 primary
1st: 3.272(11/36)
2nd: 1.937(16/31)
3rd: 1.350(20/27)
4th: 1.043(23/24)

The 2.62 primary on Z155 was PeePee Utah math. Ignore all that comes out of there, nothing but Mormons and Morons, a couple that go both ways. They spoke of "close ratio" transmissions in Gen1 Z155's, despite knowing the only change was a 17/69 primary gear set.

http://daytona-global.com/products/pdf/84346.pdf

1st: 2.6153 (13/34)
2nd: 1.7058 (17/29)
3rd: 1.3000 (20/26)
4th: 1.0434 (23/24)

 

[The_GDFP]

And, many of the gears are interchangeable among brands. A fellow might put a YX 4th on a lifan to tighten up the 3-4 for MX, or vice-versa for a street ride.

 

[Barnesd09]

Thanks for all you help Cactus and FPM. I have most most engines ratios, now all I need is the different tyre type circumference and it will all be done.
I need;
10" rim with Dirt tyre
10" rim with Motard tyre
12" rim with Dirt tyre
14" Rim with Dirt tyre

Apart from the tyres it works well in seeing the diferences between the different engines gearing and how different sproket combinations effect rpm and corner target speeds.

 

[Barnesd09]

For the finished Spreadsheet, see the first post.
Thanks to all how had an input.

 

[drb930]

Terry knows his stuff!

 

[westy465]

barnes, no honda motor? or is it the same as one of the others?

 

[Barnesd09]

barnes, no honda motor? or is it the same as one of the others?

That's the old sheet, only with china engines.
What engine are you after and I'll see if it in the new one, if not I'll put the details in for you.

 

[westy465]

just the honda 50. CCs wont make a difference if the gearbox ratios dont change will it?

 

[Barnesd09]

just the honda 50. CCs wont make a difference if the gearbox ratios dont change will it?

Nope CC's don't matter if the gearbox is the same.
I've uploaded the changes for the stock Honda crf50 3 speed. I'm not sure if its the same as the Pitster SSJ stocka, maybe some can confirm or know of what the ratios are?

 

[westy465]

cheers barnes. 15/36 FTW!

 

[The_GDFP]

Honda used a couple different primary drive ratios. 50's use a 4.056 or so and 70's a 3.72 like many of the Chinese engines. Trans ratios on the 3-speeds remained the same, I think.