Woman working on Go-Kart! Please Help

[JMaplesRush]

I bought a used go-kart for my 10 year old son the other day and everything seemed to work fine.

Specs as I know them:
Central Machinery 6.5 HP engine
Masters of Motion™ Centrifugal Clutch, 10T 41P

It kept spinning put in the grass here in the yard, and the back tire was wore out (the one that pulls as only one of them pulls), so I purchased a new tire (15x6x6) same size as the one that was on it, same type (turf tire)

Replaced 15x6x6 Sears Turf Tire
with
Tractor Supply Tire: 15x6x6 Turf Tire

*NOTE: This tire had been put on a split rim with a tube, so that's the way I replaced it. The other tire is on a regular rim, but has a tube in it as well. - Replaced that tube today. -

So, now a new tire on the one side that pulls (driver side), the old tire on the passenger side.

Still spins on take off and doesn't want to pull up a grassy hill from take off.

So, then the clutch went bad, assuming it burned up, because I had the classic symptom that it would take off on its own once started. Went to Tractor Supply today and got a 10T centrifugal clutch, got it installed. Go Kart started up and ran perfect. (Have read that you must keep one oiled, especially if you have a child riding it in a yard setting, that you have to run it at full throttle to keep it engaged and prevent it from getting hot.)

For a test run before I turned it over to my son, I took it out (I weigh 180 lbs) and within a couple minutes, the clutch was smoking. I brought it back and parked it. ... I'm at a loss now, and here's where I need your help.

Are those tires too big?

Why does it keep spinning out?

Why will it not pull up a hill from a stopped position?

Although there is no indication that the passenger tire should be installed to pull (no key hole or screw hole etc) should both back tires be pulling? I spoke to one person who said if both back tires pulled, it'd be way too hard turn.

Does a clutch come pre-oiled? (I did not oil it when I put it on, assuming it came pre-oiled and can't find that information)

How do I prevent the clutch from smoking and burning up? (I rode it fully engaged, just like I have read, but it's hard not to brake or at least let off the throttle and I know it's even harder for my 10 year old)

I've read your forum about gear ratios.
How do I know what my gear ratio is?
What should my gear ratio be?
How do I change it?

I really need to know do you think the tire is causing the issue with the clutch (the clutch didn't become a problem until new tire).

How do I ride it and/or teach my son to ride it without it being at full throttle and burning the clutch up?

There has to be a secret to kart riding that will provides endless hours of fun.

My yard is not level and is the only place for him to ride. (But he has a good acre of land of cleared land to ride on)

Some of this stuff is over my head. I can do BASIC mechanics and willing to learn if someone will just help me and point me in the right direction. I will be happy to provide any information that you may need to help me.

Thanks in advance for the help, suggestion and advice

JMR

 

[Doc Sprocket]

Welcome to the forum.

To figure out your gear ratio, count the number of teeth on the clutch, and the axle sprocket. Divide one into the other. Example- 10T clutch, 60T axle. 60/10=6, so 6:1. Those tires may be a bit large.

As for dead axle (1wd) vs live axle (2wd), yes- a live axle will typically be harder to steer. It amplifies any deficiencies in frontend geometry. With a live axle, the frontend must be well set up to steer decently. That said, it will still steer better on dirt and grass, than pavement.

The bushing in the clutch SHOULD be oil-impregnated from the factory, but it's good policy to oil before installation. Re-oil after every 2 hours' operation, with 2 drops of clean engine oil.

Getting a "feel" for your kart would be easier with a few pics...

 

[JMaplesRush]

Thanks! Will post more info tomorrow.

Thanks for the information.

I will count my axle teeth tomorrow and post.

I will also post a picture (hopefully if I can get it upload from my phone.)

Thanks for the 1wd info. It's somewhat of a relief to know that it was probably built like that and wasn't rigged by a previous owner!!

 

[Doc Sprocket]

Great! Once we have some more info, we can get you further along.

...And thanks for helping bust the stereotype!!! My wife took small engines in college, and isn't afraid to get greasy either...

 

[OzFab]

1. I took it out (I weigh 180 lbs) and within a couple minutes, the clutch was smoking.

2. Why does it keep spinning out?

3. Why will it not pull up a hill from a stopped position?

There seems to be a contradiction here: The first & last points above indicate high gearing but the 2nd point indicates more lowards low gearing. However, all can be explained as one or independant but still coming to the same conclusion:

1. The clutch is working too hard, whether it be from carrying too much weight (no, I'm not saying you're fat ), geared too high, attempting to climb hills or a combination of all three.

2. The simple answer is because turf tyres are made for lawn tractors/mowers so as not to damage grass at low speed, they're not designed for high speed applications on grass. If you want decent traction on grass, you may need to consider some knobby tyres.

3. A centrifugal clutch is not really designed for pulling up hills, that job is better suited to a torque converter so, with the combination of a centrifugal clutch, high gearing (I'm guessing) & low traction tyres, that pretty much explains everything...

 

[landuse]

I think I am with Tony on this one. Turf tyres do generally spin when on grass at high speeds. There is nothing on them to 'grip' the grass.

I also have a feeling that you are geared too high. Gearing high means that you have a numerically low number like 4:1. Gearing low means you have a numerivally high number, like 8:1. Higher gearing gives you more speed and less torque/oomph, while low gearing gives you the opposite. The higher you gear (lower number) the harder your clutch has to work to become engaged. This means that it slips a lot, gets really hot, and then gets fried. You need to find the balance between gear ratios.

On a regular yard kart, a general gear ratio is about 6:1. This gives you a good balance between speed and torque. It is only a recommendation though, and things change when you add weight, bigger tyres etc. Larger tyres is like gearing the kart higher.

I am not too sure if you have a direct drive from your clutch to axle sprocket, but you might also have what is called a jackshaft. This is used to give you a reduction in gearing using 2 more sprockets in addition to the clutch and axle sprockets. If you have this, give us the tooth counts on the extra 2 sprockets as well. I have added a pic of what a general jackshaft might look like.

Post up all the info we have asked, as well as a pic, and we will definately get you sorted. If you have a problem posting from your PC, have a look at this thread.

http://www.diygokarts.com/vb/showthread.php?t=735

If you are having problems posting from your phone or Ipad/tablet etc, then have a look here

http://www.diygokarts.com/vb/showthread.php?t=18610&highlight=pictures

 

[JMaplesRush]

Promised Information

Ok, I'm running a 6:1 ratio. Here are the pictures as promised.

 

[JMaplesRush]

Hills

Here are pictures of the ''hills'' I'm talking about.

 

[Doc Sprocket]

Pretty much what I'd expected to see. With the larger than normal tires, the size and weight of the kart (incl passengers) and the hills, the gearing is too steep. Truth be told, even if the tires were a more common, smaller diameter, it'd still be a problem. Offhand, I'd say it needs to be around 8:1.

 

[JMaplesRush]

so, Toystory...

Let me make sure I understand you correctly. Leave the tires the way they are and gear down to an 8:1 ratio. And doing so will prevent clutch burn?

Are karts meant to be ridden on tracks and flat areas for the most part?

Now, in order to replace the axle, what exactly does this require. I know I need a new chain and 80T sprocket. Is there anything else I would need to get?

With my land layout, would I in your opinion, be better off selling this one and going with a different type kart? One with a torque converter? Something like a dunebuggy? 4-wheeler?

I don't want to put a ton of money in this go-kart without being able to get the ridability out of it that I'm looking for. (Yard)

 

[Doc Sprocket]

In no order (possibly reverse order)-

Considering the variables involved, you are better off with a CVT (torque converter), whether you trade karts or adapt this one.

Depending on whether the current kart is a live axle or not (I think not, but need more rearend pics), it would be costly and difficult to convert. (more on that, if you wish).

A typical yard kart is indeed geared around 6:1, with tires at a smaller diameter (11-12") and not well suited to hilly terrain.

Gearing your current kart down to 8:1 would likely work out fairly well (as compared to now) and the clutch would be happier, but it's not what I'd call the ideal solution.

 

[JMaplesRush]

Almost finished! Thanks for all your help!!

As you explained to me in the first post, it's a dead axle.

I suppose one more question and I should be done.

Even If I change the gear ratio to 8:1, I will still not achieve the optimal riding performance for my yard that I'm looking for?

****Other than general maintenance, (which is what I know!!) I DON'T want to be working on or replacing parts every week, like I have for the past 3, since I got it (Tires, Tubes & Clutch)And, I'm tired of putting $$$ into it****

Thanks A Million! Jenn

 

[OzFab]

In short, you'd probably be better off with something like this, it already has a torque converter & knobby tyres...

Whether you sell the one you have or have the two is up to you

 

[Doc Sprocket]

I don't believe that converting a dead axle to a live axle with CVT is right for you, so we're down to 2 options: Sell, and buy another, or attempt to regear this one.

Food for thought- at 8:1 or deeper, the clutch will likely survive. There should be enough torque to make the hills. The drive tire will spin like mad from a dead start, and may or may not have sufficient traction for the hills.

Gearing down (sprocket and chain) won't cost much. Personally, I'd try it before condemning this kart.

 

[JMaplesRush]

Crazy Question for you Fabroman!

In short, you'd probably be better off with something like this, it already has a torque converter & knobby tyres...

Whether you sell the one you have or have the two is up to you

You're awesome! I love the link. I actually looked at this just a few minutes ago, but it looks like the riders legs would have to go around those bars? Am I crazy?

 

[Doc Sprocket]

Yes- but your knees will already be bent.

 

[JMaplesRush]

Many many thanks!!!

i don't believe that converting a dead axle to a live axle with cvt is right for you, so we're down to 2 options: Sell, and buy another, or attempt to regear this one.

Food for thought- at 8:1 or deeper, the clutch will likely survive. There should be enough torque to make the hills. The drive tire will spin like mad from a dead start, and may or may not have sufficient traction for the hills.

Gearing down (sprocket and chain) won't cost much. Personally, i'd try it before condemning this kart.

thank you so much for your time and effort in answering my questions. I may try changing the axle but will start looking for a more sufficient kart.

 

[qtband]

...and you don't need a completly new chain, just add the needed links
to your existing chain.

 

[JMaplesRush]

Yes- but your knees will already be bent.

What questions should I ask when purchasing a go-Kart and what should I look for?

 

[Doc Sprocket]

thank you so much for your time and effort in answering my questions. I may try changing the axle but will start looking for a more sufficient kart.

You're entirely welcome.

What questions should I ask when purchasing a go-Kart and what should I look for?

The usual stuff- verify good engine and CVT operation (test drive). The rest should be fairly obvious to you.