Templar X Sprocket re-size

ProDigit · 04-26-2024, 09:44 PM

The formula is very simple.

If 7k is your desired rpm, and your current speed is ~55 mph, and you want to be doing ~65mph at that rpm,
Your ratio change will be:
65/55= 1.182
You can either multiply the ratio with front sprocket tooth count, or divide the rear sprocket tooth count with it.

13x1.18= ~ 15T - 16T up front, or
49/1.18= ~ 41T - 42T rear.

You'll have to look and see if you can physically fit a 15-16T sprocket up front, or if you can find a 41-42T rear to buy.

Alternatively, you can also put a 14T up front, and a ~45T rear; though the easiest swap is the front sprocket.

Swapping out the front sprocket with a larger one, will mostly only affect first gear start from a stop. It does affect all gears but it'll be harder to notice. You still will have plenty of torque in the higher rpm ranges, save for final gear (5th or 6th), where torque is traded for HP; meaning your acceleration will be slower, but your top speed reached will be higher.. a taller final gear ratio, results in an increase in HP, but it only works, if the bike makes the torque necessary to pull at the speed you want to go. Hence you'll lose top end speed with taller gears if the engine isn't powerful enough to pull the gears.

A 150cc engine with carburetor usually reaches about 60-65mph tops.
A 250cc will reach about 75-80mph tops.

A fuel injected one will reach 5-10% faster than the carburetor version.

Thumper · 04-26-2024, 10:00 PM

Obviously there are a variety of ways of getting there. Now you have a few ways to calculate/estimate your preferred gearing, and make your decision. I put a smaller sprocket on the front because I ride off road and love to have rpm at low speed. So I can't tell you what might fit (bigger) up front. But you don't have to even change the front sprocket since there are many rear sprocket choices:

https://www.jtsprockets.com/catalogue/sprocket/JTR210/

In fact, these are the sprockets they are making today. There is lots of old stock apparently, like the JTR210-51 I got for my X, still available.

Just google JTR210-XX (where XX is number of teeth you want). These sprockets are low cost, and they are durable sprockets.

04-26-2024, 09:44 PM	#1
ProDigit Join Date: Aug 2013 Posts: 83	The formula is very simple. If 7k is your desired rpm, and your current speed is ~55 mph, and you want to be doing ~65mph at that rpm, Your ratio change will be: 65/55= 1.182 You can either multiply the ratio with front sprocket tooth count, or divide the rear sprocket tooth count with it. 13x1.18= ~ 15T - 16T up front, or 49/1.18= ~ 41T - 42T rear. You'll have to look and see if you can physically fit a 15-16T sprocket up front, or if you can find a 41-42T rear to buy. Alternatively, you can also put a 14T up front, and a ~45T rear; though the easiest swap is the front sprocket. Swapping out the front sprocket with a larger one, will mostly only affect first gear start from a stop. It does affect all gears but it'll be harder to notice. You still will have plenty of torque in the higher rpm ranges, save for final gear (5th or 6th), where torque is traded for HP; meaning your acceleration will be slower, but your top speed reached will be higher.. a taller final gear ratio, results in an increase in HP, but it only works, if the bike makes the torque necessary to pull at the speed you want to go. Hence you'll lose top end speed with taller gears if the engine isn't powerful enough to pull the gears. A 150cc engine with carburetor usually reaches about 60-65mph tops. A 250cc will reach about 75-80mph tops. A fuel injected one will reach 5-10% faster than the carburetor version. __________________
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04-26-2024, 10:00 PM	#2
Thumper Join Date: Feb 2021 Location: Kansas City Posts: 2,283	Obviously there are a variety of ways of getting there. Now you have a few ways to calculate/estimate your preferred gearing, and make your decision. I put a smaller sprocket on the front because I ride off road and love to have rpm at low speed. So I can't tell you what might fit (bigger) up front. But you don't have to even change the front sprocket since there are many rear sprocket choices: https://www.jtsprockets.com/catalogue/sprocket/JTR210/ In fact, these are the sprockets they are making today. There is lots of old stock apparently, like the JTR210-51 I got for my X, still available. Just google JTR210-XX (where XX is number of teeth you want). These sprockets are low cost, and they are durable sprockets. __________________ -2022 5 speed Templar X Orange, OEM 51T rear sprocket, 14T front sprocket -NOS 2020 KTM 250SX (2-stroke motocross), less than 10 hours on it
	1