Appropriate speed for an 8 year old

[Allen]

hi everyone, I'm working on a cart for my 8 year old son. Cart picture here: http://www.diygokarts.com/vb/showthread.php?t=8713

I have 12" diameter wheels on it and a 72 tooth wheel sprocket. If I put a 10 tooth clutch sprocket on it the speed calculator tells me it'll do 18 mph. I'm having a hard time picturing if this is too fast or not for an 8 year old. It seems fast... Any perspectives?

I was thinking about getting the 3hp HF engine but it seems everyone talks about the 6.5hp engine. Will the 3hp be better for a younger kid? Seems so, but maybe I'm misunderstanding things.

thanks!

-Allen

 

[landuse]

To me, 18mph does sounda bit fast for an 8yr old, but other people might disagree. If you like, you could get the 6.5 and just gear your kart so that the speed is something that your son can handle. You might need to use a jackshaft setup though, otherwise your axle sprocket might be too big for the ground clearance of your kart.

 

[Orange Krate]

My boy was driving at 7 years. 3.5hp 72tooth sprocket - ungoverned. Faster than mine governed, but he rarely went top speed, so probably just under 20. He went real slow until he got used to it then increased conservatively

 

[T-man]

Allen , I have found, with my little girl, that if they can do donuts and spit dirt all over and make dust clouds then they will have a smile on their face. I would suggest that you gear it low ( jackshaft it ) ...With a 6.5 and a 12:1 ratio with those tires he is going to love the sound and the power it has. Just my two cents.

 

[Doc Sprocket]

When I did my kids kart, I geared at 12:1. Top speed is 13MPH (with 15" tires), and is plenty for an 8-year-old. I intend to increase speed as they become proficient.

For the record- With gearing that low, the 3hp will push the kart just as fast as the 6.5hp when geared the same. Personally, Id go with the larger, more common engine with an eye toward future modifications...

 

[Allen]

thanks guys for all the input. Regarding the jackshaft, what gearing gets me to a 12:1 final ratio? 10t on the engine to 20t on the jackshaft, 12t on the jackshaft to my existing 72t on the drive wheel?

Anyone know of any pictures of jackshaft setups on carts like mine?

thanks!

 

[Simon Thomas]

My boy was driving at 7 years. 3.5hp 72tooth sprocket - ungoverned. Faster than mine governed, but he rarely went top speed, so probably just under 20. He went real slow until he got used to it then increased conservatively

Allen,

That speed is equivalent to 28-29 km/hr. I think that is fast enough for a young kid. You may compromise on his safety for a young age like your son. This is my personal opinion.

To me, with the two different hp, the rpm is still the same thus generate the same speed at that gear ratio. I am in the same opinion with Orange Krate to limit the speed by modifying the governor and pedal speed. Put adjuster there and start from low speed until you think it is safe for him to increase the speed.

 

[shakey0818]

I would say 50-65mph

 

[Doc Sprocket]

I would say 50-65mph

For an 8-year-old?
Tell me- How long have you hated children?

 

[kendelrk]

my brother was scared of my kart geared to about 30mph, i had a limiter for the petal that i coud move out of the way, it was at about 16 mph and he loved it, he had to get used to it, but he absolutley loved it,

 

[machinist@large]

I would say 50-65mph

For an 8-year-old?
Tell me- How long have you hated children?

I agree with toystory; that's just plain nuts!!

 

[cant kech me]

when i was 7 i started racing oval track karts at 45+ mph and loved it, but it was just an oval, when i was around 8-9 my built me a yard kart that ran about 35 mph and absolutely loved it, another big question is, is your kart caged? does it have seatbelts along with the cage? if safety isn't that big of deal since the kart is caged the i'd say it's pretty much there preference.

 

[r97]

For an 8-year-old?
Tell me- How long have you hated children?

I can understand 40MPH with an 8yr old, IF the kid takes a course in kart racing, has all the proper kart racing gear, is using a professionally built race kart, and has some good solid experience already.


for a standard yard kart, an 8yr old who's only knowledge on the topic is you telling them which pedal makes it stop, in an open field, for there first ride, i would suggest a MAX speed of 13 or so MPH, with a way to stop them. I'm 14 and my little minibike geared for 13MPH is a ton of fun, even though it doesn't go too fast. Let the kids practice first at low speed, then give them more speed if they want it.

 

[Bluethunder3320]

may i suggest a baja heat/warrior jackshaft plate?

bolts right onto the engine.

you might want to find it cheaper somewhere else... but this is what it looks like.

http://www.monsterscooterparts.com/bajamb165jackshaft.html

 

[JH Pinoy]

If you are planning a HF engine, and you are worried about speed, there is a rpm limiter within the throttle setup. When I let my brother about 10 yrs old ride my go kart, I limit the speed at about 10-15 mph. But if Im the one riding it I set it back up the way I got it. about3600 rpm. I hope that helps.

 

[Badot]

Limiting the revs, travel of the throttle, etc, is not usually advised as the lower max revs is likely to cause excessive slippage in a clutch and potentially damage it.

 

[Doc Sprocket]

Limiting the revs, travel of the throttle, etc, is not usually advised as the lower max revs is likely to cause excessive slippage in a clutch and potentially damage it.

Whenever possible, use kart setup and gearing to limit speed. Throttle tricks should be reserved for MINOR limitation.

 

[kendelrk]

saftey is always over speed, would you rather your little brother fall off at 40 + or work his way up from there till he can do it saftley and calmley?

 

[cant kech me]

Good if your dads speeding tickets are 125-137, like mine.

He does not hate them , he's like my dad speedy guns.
No, When I was 8 (I'm 12 now) My dad let me go 110 in a field in his 71' mach one mustang!!! It was exalerating!!!

Slow poke!!!!


How can u like to go so slow???

Try 110, I tell u it's a different animal.

alright genious, driving a car is completley different, way easier to drive at speeds, and plus, its 46234625625x's safer, and yes, i've driven that fast, i would rather drive a go kart at 60, simply because of how close you are to the ground. and how simple it is.

 

[r97]

South Kart3377,

Is it just me or are your not getting the point of this thread at all?