Sprocket Gearing Ratio?

[dreazoian]

Alright so recently ive been trying to figure out my sprocket gearing ratio. It has a 45 tooth axle sprocket and a 10 tooth clutch sprocket. What would the gearing ratio be. And i have a tecumseh powersport 6hp engine. With the ratio that it is at now, how fast should my go kart be going at max speed? If it helps, my front wheels are 13 inches and the back ones im not sure about but its a Yerf-Dog 3020. and i weigh 200lbs. Is there any other info you would need to determine the top speed?

 

[landuse]

You can have a look at the speed calculator. If your engine has its governor still, you should use 3600 as the RPM

How it basically works is that if you have a clutch going straight to your axle sprocket, you work it out like this

(axle sprocket tooth count/clutch tooth count) = *:1

Yours would be

45/10 = 4.5:1

This is waaaaay high. You will fry your clutch in less than 2 seconds. I am assuming you have a centrifugal clutch. Those yerf dogs generally came with a torque converter with a jackshaft. It sounds like yours has been modified to go straight from the clutch to the sprocket. You are going to have to have at LEAST a 6:1 (IMO it should be lower like 7 or 8:1). This means that without a jackshaft you might have to get a axle sprocket which is really big which could potentially scrape on the ground

All I have said is pretty useless without us knowing more about the tyre size, what has been done to the drivetrain, etc

Post some pics of it so that we can help you out some more

 

[dreazoian]

You can have a look at the speed calculator. If your engine has its governor still, you should use 3600 as the RPM

How it basically works is that if you have a clutch going straight to your axle sprocket, you work it out like this

(axle sprocket tooth count/clutch tooth count) = *:1

Yours would be

45/10 = 4.5:1

This is waaaaay high. You will fry your clutch in less than 2 seconds. I am assuming you have a centrifugal clutch. Those yerf dogs generally came with a torque converter with a jackshaft. It sounds like yours has been modified to go straight from the clutch to the sprocket. You are going to have to have at LEAST a 6:1 (IMO it should be lower like 7 or 8:1). This means that without a jackshaft you might have to get a axle sprocket which is really big which could potentially scrape on the ground

All I have said is pretty useless without us knowing more about the tyre size, what has been done to the drivetrain, etc

Post some pics of it so that we can help you out some more

Yea i have a torque converter, and yes it just goes from the clutch to the sprocket. I have been riding it like this ever since i got it and the acceleration is somewhat slow but not extremely slow and i hit speeds of ATLEAST 35+. And so the way mine is set up, it does not have the input and output sprockets on the jackshaft. Is it bad that ive been driving it like this? I will find out the exact wheel size tomorrow. But im almost sure it is 18". I have no clue what has been done to the drivetrain or anything because i am the second owner of this kart. i bought it used off craigslist.

 

[landuse]

Yea i have a torque converter, and yes it just goes from the clutch to the sprocket. I have been riding it like this ever since i got it and the acceleration is somewhat slow but not extremely slow and i hit speeds of ATLEAST 35+. And so the way mine is set up, it does not have the input and output sprockets on the jackshaft. Is it bad that ive been driving it like this? I will find out the exact wheel size tomorrow. But im almost sure it is 18". I have no clue what has been done to the drivetrain or anything because i am the second owner of this kart. i bought it used off craigslist.

It is not a bad thing driving it like this. The only problems that you might see is that you will wear belts out faster than you normally do. A Torque Converter can usually handle higher gear ratios than centrifugal clutches. If you want a little more ooompf, you can get a larger axle sprocket

 

[dreazoian]

It is not a bad thing driving it like this. The only problems that you might see is that you will wear belts out faster than you normally do. A Torque Converter can usually handle higher gear ratios than centrifugal clutches. If you want a little more ooompf, you can get a larger axle sprocket

And by more "oomph" you mean torque right?

 

[dreazoian]

All I have said is pretty useless without us knowing more about the tyre size, what has been done to the drivetrain, etc

Post some pics of it so that we can help you out some more

Alright here are some pictures of the sprockets on the Driven and the axle. The kart has 18 inch wheels. There is about about 4.75 - 5.00 inches of space between the ground and the axle sprocket so if necessary, i could probably get a little bit bigger with the sprocket. The chain goes straight from the 10 tooth sprocket on the driven to the axle sprocket.
EDIT: My engine currently isnt on the kart because im selling it so it might look weird

 

[OzFab]

As landuse already pointed out, you could do a lot better with a bigger axle sprocket. If you go for something around 60t, you'll definitely notice the difference.

However, in doing so, you will lose top speed but, you'll get there a lot quicker...

 

[dreazoian]

As landuse already pointed out, you could do a lot better with a bigger axle sprocket. If you go for something around 60t, you'll definitely notice the difference.

However, in doing so, you will lose top speed but, you'll get there a lot quicker...

But in order to get a 60t axle sprocket, wouldn't it be a big hassle? Sorry lol im fairly new to go karts so i really do not know how i would change one. Do i need to completely change the axle?

 

[OzFab]

No but, you will need to remove the axle.

Remove the axle, remove the sprocket from the axle, take it to your local Tractor Supply & tell them you want the same thing in a 60 tooth...

 

[dreazoian]

No but, you will need to remove the axle.

Remove the axle, remove the sprocket from the axle, take it to your local Tractor Supply & tell them you want the same thing in a 60 tooth...

Sounds easy, just one problem.. i cant get one of my rear wheels off so any tips on how i can get it off? i have tried oiling it, leaving it overnight, hitting it with a hammer, pulling it, kicking it. basically everything i can think of but no luck.

 

[OzFab]

Well, you're in luck coz you only need one wheel off; you should be able to get to the bearing hangers with the wheels in place then, once you remove the axle, you can worry about getting the stubborn wheel off if you so desire.

Are you having trouble removing the nut or removing the hub from the axle?

 

[dreazoian]

Well, you're in luck coz you only need one wheel off; you should be able to get to the bearing hangers with the wheels in place then, once you remove the axle, you can worry about getting the stubborn wheel off if you so desire.

Are you having trouble removing the nut or removing the hub from the axle?

Wow thats a relief! And i got the nut off with no problem, its the dang hub! Its rusted and even the other wheel that i got off, nothing was oiled or anything before they were put on. And honestly, do you think it would be worth changing the sprocket to get more torque because as long as i dont have a suspension, i doubt i will go offroading so i wont need major torque. I WANT a suspension but the problem is, to get a decent full suspension, how much cash would i have to spend? sorry for all these amateur questions, but i have learned alot so far

 

[landuse]

Wow thats a relief! And i got the nut off with no problem, its the dang hub! Its rusted and even the other wheel that i got off, nothing was oiled or anything before they were put on. And honestly, do you think it would be worth changing the sprocket to get more torque because as long as i dont have a suspension, i doubt i will go offroading so i wont need major torque. I WANT a suspension but the problem is, to get a decent full suspension, how much cash would i have to spend? sorry for all these amateur questions, but i have learned alot so far

And by more "oomph" you mean torque right?

Yup.

It is all up to you. If you are happy with the performance of the kart at the moment, then don't 'fix what aint broke'.

Suspension will cost you some money cos you are going to have to buy shocks and all the other bits and pieces that are going to be needed for the conversion. You are also going to need some fabrication skills, so if you are not too confident, and you are happy at the moment, then I would leave the whole thing.

 

[dreazoian]

Yup.

It is all up to you. If you are happy with the performance of the kart at the moment, then don't 'fix what aint broke'.

Suspension will cost you some money cos you are going to have to buy shocks and all the other bits and pieces that are going to be needed for the conversion. You are also going to need some fabrication skills, so if you are not too confident, and you are happy at the moment, then I would leave the whole thing.

Alright thanks alot for your help!