ATC 200 transmission ratios

[Gabriel]

Does anyone have, or know a source for the transmission ratios for the 200cc engines? I'd like to know them all (assuming there's a difference) but SPECIFICALLY the 200E. That would be (10) total. 5 speed, high and low.

I'm stuck with the front sprocket. There's just no swapping it except for another just like it. Weird bastardized set up that thing is. BUT, I am trying to figure my rear sprocket. It's gonna be a while before it's running but I'd like to play with some numbers.

[ironchop]

Does anyone have, or know a source for the transmission ratios for the 200cc engines? I'd like to know them all (assuming there's a difference) but SPECIFICALLY the 200E. That would be (10) total. 5 speed, high and low.

I'm stuck with the front sprocket. There's just no swapping it except for another just like it. Weird bastardized set up that thing is. BUT, I am trying to figure my rear sprocket. It's gonna be a while before it's running but I'd like to play with some numbers.

Usually, it's in the front chapter of a factory Honda manual in the specifications section for nearly everything I've ever worked on that was a Honda off road product.

Have you checked one of those yet?

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[Gabriel]

Owww. My head hurts!!!


I had to use 3wheeler manuals .com to find them. ......now, I have to learn meself WTF all that means. Primary reduction, final reduction. I don't even see the sub transmission reduction. AArrrrrr....too much math.

[ps2fixer]

Another source for manuals is http://www.oscarmayer.net/atc/manuals/

For the gear ratio math, just think of it in terms of engine rpm vs mph on the tires. You just have to run though all the ratios. What exactly are you trying to calculate out? The stock sizes are generally good unless you're changing tire sizes.

To simplify the meanings, the primary reduction ratio is the engine crank vs transmission input shaft. Transmission gearing is input shaft vs output shaft (into transfer case). If I'm thinking right, the final reduction should be the chain sprocket front vs rear and that finally gives you axle rpm or tire rpm which speed is based on tire size at that point. I'm thinking the gear ratios given are high rang , and the number in the parentheses is low range. It's labeled as Posi-torque gear ratio, which is a weird way to say low range.

Just to start the math off, 6k crank rpm -> 1800rpm for trans input rpm -> 5th gear 0.815 ratio = 2209rpm trans output (front sprocket I guess) -> 516.9rpm axle rpm. To get MPH there's a little extra math needed for the tire.

Assuming 25in tall tire. 2 * radius * pie = circumference. So 25 * 3.14 = 78.5in around. or distance traveled per turn of the tire. Multiply that number by the tire rpm and we get 40577in per minute. Divide by 12 to convert to feet = 3381.4ft per min. Now convert to miles, 3381.4/5280 = 0.641 miles per min. Now convert it to hours so * 60 = 38.4mph.

The number seems reasonable but very possible I got something wrong. It's been a really long time since I did that type of math, I made a program when I was like 11 to run through that math and it took me forever to get it right. If you know how to use "functions" in a spread sheet you can put all the math in that and just change a few numbers for inputs. You could also do the math in reverse if you have a target mph to find what engine rpm would be required at the given ratios.

Here's the math a little more "normal" and less wordy, might be easier to follow.

6000/3.333 = 1800
1800/0.815 = 2209
2209/4.273 = 516.9
25*3.14 = 78.5
78.5 * 516.9 = 40577
40577/12 = 3381.4
3381.4/5280 = 0.641
0.641 * 60 = 38.4

[Gabriel]

Ok, so primary reduction is the ratio between the crank and the transmission input. The 1 thru 5 ratios are the selected gear outputs. I see those listed but I also see a Final Drive ratio. What's that? AND, they do not list the gear reduction ratio for the High/low range of the sub transmission. I'm guessing the High range is just 1:1 with no reduction. The low range is obviously geared down but I can't find out how much.

I have a couple of different sprockets here I can try and they're pretty easy to swap. Wide open High/5th I'd never need more than 35-40 mph IF that. I need to go see what the tooth count is on my sprockets.

[ps2fixer]

Normally when I see final reduction I think ring and pinion, so the only thing that makes sense is front sprocket vs rear sprocket. I found a pic in the service manual of the front sprocket, looks like 11 or 12 tooth. I multiplied that by the final gear reduction and the math with 11 front works out best. I'm guessing it's 11 tooth front and 47 rear. 47/11 = 4.2727272727 or 4.273 if rounded.

I'm not sure if these engines normally rev out to their max rpm in highest gear, or if they are limited by their power output vs wind resistance. 6k rpm isn't a bad figure, but peak HP is at 7k rpm, however peak torque is at 5500rpm. If the engine does 7000rpm, and all the math the same as before, max speed would be something like 44.8mph.

With your sprocket options you have on hand, devide rear by front to get the ratio, then you can find the ratio between stock vs your new ratio and use that number to multiply against the mph numbers if you wanted to skip the other math.

aka if you have a 50 tooth rear, 50/11 = 4.545, then ratio between that and 4.273 is 0.94 or about 6% slower speeds. 44.8 * 0.94 = 42.1mph. You can get similar effects with tire size too, aka 10% reduction in tire size ends up giving 10% lower speeds too.


For the high vs low range, I'm thinking it's the () number. Like 5th gear is 0.815 in high, or 1.125 in low. Numbers don't match up exactly though but are all close when the main ratio is multiplied by 1.38.