Son's Birthday project HELP

[DirtySCREW]

I got a go cart frame yesterday with a blown motor for parts. I plan on getting a HF Predator 6.5 HP motor new.
The old motor and axle have a belt type system on it. I want to convert this to a chain and sprocket setup. Can you help or give advice? This is my first go cart build if you will. It for my son's birthday and he turns 5 in about a week. It is a 2 seater frame.
Here's the frame:

Thanks

DirtySCREW

 

[landuse]

Welcome to the forum. Thay is a nice looking frame you have there. You are going to have to take the pulley off the axle and see if the axle is keyed.

With your large tyres, gearing is going to have to be thought of carefully. If your son is just going to be doing onroad karting, then I would suggest a centrifugal clutch with 10 teeth and a axle sprocket of about 70T. This will give you a gear ratio of 7:1, which should be OK with those tyres.

Post some close up pics of the axle. Have you got brakes on the kart?

 

[Nodroz]

That's a nice frame, indeed! What's wrong with the engine? Maybe you could try to get it back running?

Your tyes are pretty big, so I would suggest a gearing of 7:1n like Landuse said before.
However, beacuse your son is only 5 years old, I'd gear it lower so it doesn't go as fast.

 

[OzFab]

Welcome to the forum. Thay is a nice looking frame you have there. You are going to have to take the pulley off the axle and see if the axle is keyed.

With your large tyres, gearing is going to have to be thought of carefully. If your son is just going to be doing onroad karting, then I would suggest a centrifugal clutch with 10 teeth and a axle sprocket of about 70T. This will give you a gear ratio of 7:1, which should be OK with those tyres.

Post some close up pics of the axle. Have you got brakes on the kart?

Personally, I would stick with the belt drive setup for now & consider a chain drive setup later if you're not happy with it.

That's a nice frame, indeed! What's wrong with the engine? Maybe you could try to get it back running?

Good question! Nothing's unfixable

Your tyes are pretty big, so I would suggest a gearing of 7:1n like Landuse said before.
However, beacuse your son is only 5 years old, I'd gear it lower so it doesn't go as fast.

Those wheels don't look stock, they seem oversized for that type of kart. Not a big deal; to a point they will work in your favour. I also agree with a lower ratio, @ 7:1 it may freak out the young fella; you don't want to scare him off...

 

[mysteryboy28]

i see that kart and i redesign it a LOT in my head. move the rear axle bearings to the top of the frame, rather than the bottom (quick slice n dice the bearing hangers with a metal cutting disc, then re-weld) otherwise the kid will be sliding out of his seat all the time. that stance angle is too steep. then ditch the belt pulley, make sure you have a 1/4" keyway on the axle for a 70t sprocket (is the axle a 1" rod?). then if you want to do it RIGHT - get a torque converter, NOT a centrifugal clutch. as the kid gets older he'll appreciate it - especially riding in tall grass and up hills. centrifugal clutches have no balls, and burn out easily.

 

[Jcotz]

Mysteryboy28:
You have to understand that he is probably working within the constraints of a budget, and not every one can just splurge and get a $200 torque converter. Although they are more effective, it is not always feasible.

 

[r_chez_08]

With your large tyres, gearing is going to have to be thought of carefully. If your son is just going to be doing onroad karting, then I would suggest a centrifugal clutch with 10 teeth and a axle sprocket of about 70T. This will give you a gear ratio of 7:1, which should be OK with those tyres.

His son is 5, that is gearing for way too much speed! Unless the OP plans to ride with his son the whole time.

Can I suggest leaving the belt setup for now, so your son can ride it on his birthday? If you can get the engine running, great! Then he can help you upgrade it. A bonding project

What is your budget with this kart?
What I would do-
*Buy a 6.5hp predator for $99 on sale
*Get a comet torque converter for $140-200 (depends if you buy genuine, chineese, kit or non kit)
*Get a sprocket for the axle, as well as a jackshaft to allow you to gear down $50.
*Mount the bearings on the top side of the frame so the kart sits more level.
*Get a piece of plywood, some foam, vinyl and a staple gun. Make a seat.

Total cost around $300-350. You could fix it up cheaper, by using a $25 centrifugal clutch, but its up to you.

Offtopic: Mystery boy- your display picture is seriously messed up!

 

[Doc Sprocket]

7:1 is way, waaay too high for a 5-year-old, unless he has prior experience. I believe the situation calls for a jackshaft to allow compound gear reduction, probably somewhere between 12:1 and maybe as low as 16:1.

Dirtyscrew, please give us the overall diameter of the rear tires, as measured from the ground to the top of the tread. From there, we can toss some tangible numbers around. Welcome to the forum!

 

[souperman000]

i see that kart and i redesign it a LOT in my head. move the rear axle bearings to the top of the frame, rather than the bottom (quick slice n dice the bearing hangers with a metal cutting disc, then re-weld) otherwise the kid will be sliding out of his seat all the time. that stance angle is too steep. then ditch the belt pulley, make sure you have a 1/4" keyway on the axle for a 70t sprocket (is the axle a 1" rod?). then if you want to do it RIGHT - get a torque converter, NOT a centrifugal clutch. as the kid gets older he'll appreciate it - especially riding in tall grass and up hills. centrifugal clutches have no balls, and burn out easily.

Mysteryboy28:
You have to understand that he is probably working within the constraints of a budget, and not every one can just splurge and get a $200 torque converter. Although they are more effective, it is not always feasible.

He also has a time constraint if he wants to get it done for his son's actual birthday.

I would just get it operable for is birthday and then mess around with it after.

 

[DirtySCREW]

Thanks for all the replies guys!
I went and got a 6.5H Predator today from HF.

I do plan on riding (driving) with my son at first, or let his big sister drive some.

I do not understand the belt system. There is the assembly on the axle and on the old motor that appears to hold 3 belts???? Or is that just gear ratios for a belt setup? Forgive my ignorance on what they are called.
I've been told I could get belts at Tractor supply (30-45 minutes away from me).

I definitely need to also need to figure out the MOST important system--BRAKES!!!!
I saw 2 different drum setups at Northern Tool the other day...and then I know there's the disc setup.

Keep the help and ideas coming.

--DirtySCREW

 

[r_chez_08]

I would go disc brakes. BMI sell some cheap discs.
The different pullies are to change the ratio. You only need one belt at a time.

 

[landuse]

However, beacuse your son is only 5 years old, I'd gear it lower so it doesn't go as fast.

I also agree with a lower ratio, @ 7:1 it may freak out the young fella; you don't want to scare him off...

His son is 5, that is gearing for way too much speed! Unless the OP plans to ride with his son the whole time.

Offtopic: Mystery boy- your display picture is seriously messed up!

I totally agree with the display pic. I haven't liked it from the start.

7:1 is way, waaay too high for a 5-year-old, unless he has prior experience. I believe the situation calls for a jackshaft to allow compound gear reduction, probably somewhere between 12:1 and maybe as low as 16:1.

Sorry guys,I missed the kids age when I read the original post. Thanks for correcting me.

 

[MidLife]

Just curious how you would move the bearing hangers to the top of the frame?
Would that not put the axle running right across the engine mount?
What am I missing here?

 

[landuse]

Just curious how you would move the bearing hangers to the top of the frame?
Would that not put the axle running right across the engine mount?
What am I missing here?

You would have to rework the motor mount as well. It is not worth the effort

 

[r_chez_08]

Just curious how you would move the bearing hangers to the top of the frame?
Would that not put the axle running right across the engine mount?
What am I missing here?

Sorry buddy, it's me that's missing something
I didn't look at the pics well enough. It is doable as landuse said, but not really worth it now I look properly.

 

[MidLife]

Maybe smaller rear wheels would be an easier option.

 

[DirtySCREW]

Maybe smaller rear wheels would be an easier option.

Yea, I was thinking of some smaller rear tires. The ones on it now are the large rear tires from a riding lawn mower. If I can find some smaller ones that aren't too expensive...


--DirtySCREW

 

[OzFab]

Have a look around on these two sites, I'm sure you'll find something suitable

http://www.gokartgalaxy.com/wheel_tire_combos.htm

http://www.bmikarts.com/category/Tires--Rims-621

 

[DirtySCREW]

Just measured the rear tires and they are 19" tall.

I pressured wash the frame yesterday. The belt thinga ma jig is WELDED onto the axle. So it looks like I'm gonna have to get a new axle. I don't know if I should try to get a different rolling frame and stick my new motor on that or what. I still need brakes and a sprocket for this one. AHHHHHHH
This one looks like it may nickel and dime me to death.

---DirtySCREW

 

[Doc Sprocket]

The belt thinga ma jig is WELDED onto the axle.

KILL!!! I desperately hate it when folks do that. NEVER weld something on that you may have to remove in the future! Furthermore, never weld on something that may have it's temper ruined by the heat.