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View Full Version : Can someone help me with some gearing calculations?


stevensj13
08-21-2012, 10:27 PM
Hey guys. I'm building an XR 80 shifter cart out of an old beat up roller go cart frame and a soon to be unsiezed XR 80 motor :rolleyes:. Anyway, It might be the gas fumes or I might just be stupid but I can't for the life of me figure out the gearing. Could someone tell me what my top speed would be in each gear with the following specs?

1989 Honda XR 80 motor

Primary reduction: 4.438
Final reduction: 3.571
1st gear ratio: 3.083
2nd gear ratio: 1.882
3rd gear ratio: 1.400
4th gear ratio: 1.130
5th gear ratio: 0.923

14 tooth front sprocket (on motor)

60 tooth rear sprocket (on go cart axle)

13 inch tall tires.
MonroeMike
08-21-2012, 11:16 PM
I have a manual, I'll get it uploaded somewhere, so you can get it.
stevensj13
08-22-2012, 12:13 AM
I have a manual, I'll get it uploaded somewhere, so you can get it.

Thanks! It has the gearing ratios I need in it.
Redlunn
08-22-2012, 10:54 AM
I have a spreadsheet that I made for the 1000x that calculates the speed in MPH for each gear at a given engine RPM. Could probably modify it for your application once you get all the info. Its currently a Google doc but I can copy it to Excel later if interested.

153045
stevensj13
08-22-2012, 11:07 AM
I have a spreadsheet that I made for the 1000x that calculates the speed in MPH for each gear at a given engine RPM. Could probably modify it for your application once you get all the info. Its currently a Google doc but I can copy it to Excel later if interested.

153045

That would be perfect. What other info do you need? I can get it for you. I've got the primary and final drive ratios, along with all the gear ratios out of the manual posted in my 1st post. I'm running a 14 tooth front sprocket, 60 tooth rear sprocket, and 13 inch tall tires. The stock engine revs to 10k RPM, if that helps. Thanks
Redlunn
08-22-2012, 06:07 PM
This is what I came up with based on your numbers. The spreadsheet is attached if you want to try jacking with the sprocket ratios or engine RPM.

153065

153066
stevensj13
08-22-2012, 06:22 PM
This is what I came up with based on your numbers. The spreadsheet is attached if you want to try jacking with the sprocket ratios or engine RPM.

153065

153066


Alright thanks! Yeah looks like I'm gonna have to regear, that'll work for now but a 40 someodd tooth sprocket might give me a better ratio. And also thanks for the spreadsheet so I can mess around with it.