having problems with my new go kart

[joshtaylor82]

just built a go kart from the ground up, rode for the first time yesterday, has poor acceleration and after it actually go to moving the cintrifigal clutch was smoking and had turned whiteish grey on the outside, was thinking i may need a more heavy duty clutch, but after reading a few posts on here i am not so sure anymore, any thoughts or suggestions would be much appreciated, thank you

 

[Doc Sprocket]

You're geared too tall. We need to know:

1) Overall rear tire diameter
2) Tooth counts on all sprockets
3) Engine size
4) Kart description (size, weight etc.) Pics would help too

A "heavier duty" clutch would be a waste of money. You probably WILL need a new one now, but that doesn't change the issue.

 

[joshtaylor82]

the overall tire diameter is 22" on 12" wheels, the wheels and tire came off of a 4 wheeler, clutch is a 10 tooth axle sprocket is a 54 tooth, i have a 7hp briggs and straton engine on it as far as a description it is about 7' 6" long and about 3' 6" wide, i would guess it is about 200+ lbs cause the tires and wheels themselves wiegh alot, frame is made out of 1" round tubing

 

[Doc Sprocket]

Yup, gearing. For something like what you have to really be workable, you need a CVT. I suggest a Comet 40. Still, you'll have to gear a bit deeper. With tires that big, in order to continue to run a centrifugal clutch (without carnage), you'd have to gear way down low- so low, the fun factor would take a major hit. So- CVT and gear down a bit, or- much smaller tires and centrifugal clutch (and still likely have to gear down some, most likely requiring a jackshaft).

Oh yeah- Welcome to the forum, too!

 

[joshtaylor82]

ok so even if i went with smaller whees and tires i would need to gear down, and when you say gear down, does that mean larger sprockets or smaller sprockets (i'm new at this so i really dont quite the gearing side of it yet), and what exactly is a jackshaft, is the any way to keep from having to gear it down

 

[joshtaylor82]

Here are a couple pics of the kart

 

[kaymo]

haha wow i like the kart but yeah you are gonna need better gearing to push that sucker. honestly if it were me, id go for a four wheeler motor as well. not that you cant use this type of motor, but like they said, you have to gear it properly.

this is the same design i envisioned when i first thought about what kind of go kart i wanted. with lots of flex for jumping stuff

 

[landuse]

ok so even if i went with smaller whees and tires i would need to gear down, and when you say gear down, does that mean larger sprockets or smaller sprockets (i'm new at this so i really dont quite the gearing side of it yet), and what exactly is a jackshaft, is the any way to keep from having to gear it down

When someone says gear down, it means that the ratio will get larger. For example, you have a (54/10) = 5.5:1 ratio. That is a bit high. (the lower the ratio, the higher the gearing). If you get a larger rear sprocket, say a 70T, your gearing will be lower at 7:1. The lower you gear, the more torque you will have, but speed will be sacrificed.

A jackshaft is used for compound gearing. They are usually used to give you more gearing options, and to save space. You can realistically only get a certain size tooth count for your rear axle before it starts scraping the ground. With a jackshaft, you can get a lower gear ratio with smaller sprockets.

These are some pics of the jackshaft I used on my minibike.

 

[joshtaylor82]

so, would i just keep the same sprockets and just add the jackshaft, or do i still need to change the axle sprocket, and how much differenc would it make if i were to use smaller wheels and tires

 

[fowler]

killer kart
probs could use a bit more triangulation

it is a shame u dont have the engine from the quad
it would be perfect

id have to go with toystory
u need a cvt

if u used smaller tryes it would help alot butthe shear size and weight of the kart is still an issue
a jack shaft would invole a bigger axle sprocket on the axle

if i was u id erase any future errors and get a cvt
by the time u have purchased a jackshaft, new sprockets and smaller tryes u will almost have spent as much as a cvt but have made the kart into something your grandmother would call slow

if it were my kart
id strengthen the frame a bit more and add a 250cc bike engine
then it would fly

 

[landuse]

If you are going to stay with the centrifugal clutch, you could probably use the axle sprocket. All you have to do is figure out what other sprockets are needed to give you a decent ratio. I would also still get smaller wheels. The calculation for a jackshaft works like this:

(JS in/clutch) * (axle/JS out) = ratio. (You always want to divide the larger by the smaller. You would ideally like to get a ratio of at least 6-7:1. I would also get smaller tyres.

So you would do something like this (depends what size sprockets are available).

(18/10)*(54/14) = 6.94:1

Here I used an 18T sprocket as the JS in, and a 14T as a JS out. I kept your clutch at 10 and your axle sprocket at 54. There are so many combinations tht can be used. You just have to see what is best for you.

 

[joshtaylor82]

if i use a torque converter will i still need to change the gear ratio

 

[joshtaylor82]

so if i go with a jackshaft, i can get a kit that comes with a 10 and 14 tooth sprockets online and if i figured right i would end up with a 7.65:1 gear ratio (does that sound right), with the 14 tooth as the js in and the 10 tooth as the js out, would that work if i kept the same wheels and tires of will i still have problems, and need to reduce wheel and tire size

 

[joshtaylor82]

sorry for all the questions, this is my first build and i have already done the gearing wrong once and i just want to make sure that i get it right this time before i go and waste money on possibly the wrong stuff, so all your help and advise is and has been much appreciated, just dont want to waste money that i really cant afford to waste

 

[sparky]

What we really need here is more motor!

 

[landuse]

so if i go with a jackshaft, i can get a kit that comes with a 10 and 14 tooth sprockets online and if i figured right i would end up with a 7.65:1 gear ratio (does that sound right), with the 14 tooth as the js in and the 10 tooth as the js out, would that work if i kept the same wheels and tires of will i still have problems, and need to reduce wheel and tire size

You have done the calculation correctly. The only problem is that there are so many variable that come into play, such as rider and kart weight, tyre diameter etc. It is a little difficult for me to say that this ratio will be good for you and your kart or not. I had to gear my minibike from 8 to 11 before I got any sort of performance out of it. I think it was my wheel diameter though that made me have to gear so low. A ratio of 7.65 is definately better than what you had, but with those size tyres I would not like you to go and buy a jackshaft on the advice that I have given you.

There are more knowledgeable people on this forum than me, so maybe hang on for a day or two more for them to give their opinion as well. You could maybe PM Toystory if you like. He knows his stuff.

If you get a TC you will probably have to do a little bit of gearing as well. I have never used one, so I am not too familiar with them

What we really need here is more motor!

I don't agree with this statement. No matter what size engine you have, if your gearing is incorrect you will still have a problem.

 

[joshtaylor82]

well i have found a jackshaft kit that will get my gear ratio to like a 10.4:1, so im thinking that should definately move the thing

 

[landuse]

Yup, I think you will probably be good to go. Don't expect high speeds though. Gearing low robs speed but boosts torque.

 

[joshtaylor82]

so i got mey gear ratio lowered, tried it out over the weekend and it took off great and was a blast, i just want to thank everyone for all the help and input

 

[landuse]

so i got mey gear ratio lowered, tried it out over the weekend and it took off great and was a blast, i just want to thank everyone for all the help and input

Great!!! I am glad we could help you out. You learn a lot of stuff on this forum