How to slow down a kart?

[jfoust]

I know this place is mostly people asking about going faster, but I want to go slower! Here's what I'm working with:

It's a two seater with a live axle. I slapped a 6.5HP Harbor Freight clone on it. The governor is still on it - the only change I made was adding the AGK throttle kit. The old sprocket was a little worn, and bent too, so I was going to replace it and decided to just do it all - sprocket, clutch, and chain. Here's what it's running:

10T clutch
60T sprocket (7.25" OD)
12" tires

Problem is with me in it (225lbs) I went out with the GPS and it's hitting right at 40mph! That's not a problem for most folks, but I was planning on turning the kids loose on this thing. Certainly not at those speeds! I know I can adjust the throttle stop and go to a bigger sprocket, and that will help, but is there anything else I can do to slow her down?

BTW, 40MPH on that thing is a total blast!

 

[freakboy]

put a wood block infront of the gass pedal so it tops out at what ever speed you want for them but take it out for your inner speed demon.

 

[jfoust]

Duh! That would work! Should this setup be going that freaking fast? I plugged the numbers into the calculator and came up with something closer to low 20's. On my first ride, it didn't quite feel like 20 so that's when I went for the GPS!

 

[slideways]

The clone has a nice little throttle limiter on it. Look at the big lever you would use for a pump or pressure washer etc.. when you move it to full throttle part of it contacts a little phillips head screw on the top plate. As you can easily figure out, adjusting that screw will only let that lever move so far. I'm not sure how the AGK throttle setup works but i would guess that lever is still there and you should be able to do this.

 

[Chupacabra]

Wow. 40 mph? Nice! I have a 2 stroke 1978 Puch Maxi Luxe Moped(pedals) with a 70cc kit and pipe. It was built to do 25 stock. It does 45 modded. Scary as he'll on a frame no bigger than a BMX bike. I bet 40 on that thing feels like 60! Be careful. Hope you got a helmet.

 

[jeremybentham]

Nice ride bro. Was that originally a one seater? Is it a Ken-Bar?

 

[Linksep]

Did you accidentally enter 10" (wheel size) instead of 20" (tire size) in the calculator?

If you have a Max Torque or Hillard clutch you can buy replacement drive sprockets (10T-19T depending on clutch) from www.mfgsupply.com that'll slow it down.

 

[mike75925]

looks like a factory two seater. have you opened the engine to see what parts are in it?

 

[vgk]

I think it is a ken-bar streker
I have one but I dont think I go 40 MPH! Have fun and be safe!

 

[Linksep]

Wait a tick... I screwed up on my last post... More teeth on the clutch will make it faster...

I call shenanigans. I don't think it'll do 40MPH with a 10t-60t drive and a 6.5 clone @ 3600rpm. You would need 22" tires to get there. Either the governor is screwed up (made in China = decent possibility), you have the throttle set up in a manner that disables the governor (no spring), or you're pulling our legs.

If you have the throttle cable hooked up so it won't let the governor do it's job, then I see 39MPH by the calculator with a 14.7" tire if the engine runs up to 5300 RPM (valve float, governor not working it's magic).

 

[bajagokart]

gear it down lol simple answer

 

[jfoust]

Wait a tick... I screwed up on my last post... More teeth on the clutch will make it faster...

I call shenanigans. I don't think it'll do 40MPH with a 10t-60t drive and a 6.5 clone @ 3600rpm. You would need 22" tires to get there. Either the governor is screwed up (made in China = decent possibility), you have the throttle set up in a manner that disables the governor (no spring), or you're pulling our legs.

If you have the throttle cable hooked up so it won't let the governor do it's job, then I see 39MPH by the calculator with a 14.7" tire if the engine runs up to 5300 RPM (valve float, governor not working it's magic).

I'm telling you it hauls serious A$$... No shens here. I have a camera clamp - going to get a video of it going wide open. I didn't think it would do that kind of speed either until I took it for a spin with my GPS on board.

I don't think the governor is doing its job - it sounds like it's revving over 3600. I didn't monkey with it during the throttle kit install, but it's possible that it's not hooked up correctly, etc.

As for some of the other questions, jeremybentham - it's been a two seater as long as I've had it... Don't know if it was reconfigured at some point by a prior owner or what, but with the steering wheel layout I think it's always been a 2 seater.

slideways - that's what I was thinking about doing - just limiting it there, but I just wanted to make sure something wasn't goofed up on the motor (think it might be the governor spring or something)..

Thanks everyone for the responses!

 

[mike75925]

whatever you end up doing, pray your kids don't see you tweaking on it. they always seem to know what to do to get it where they want it.

 

[Linksep]

I don't think the governor is doing its job - it sounds like it's revving over 3600. I didn't monkey with it during the throttle kit install, but it's possible that it's not hooked up correctly, etc.

That's what I'm thinking... The throttle cable needs to be attached to the throttle plate via a soft spring somewhere. The governor needs to be attached to the throttle plate by some rigid means, and the governor arm must be able to over-power the throttle spring.

If they have Northern Tool down there in GA you can pick up a tach for $33 http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200319029_200319029

Otherwise, Harbor Freight sells a digital multimeter with Tach pickup for $37 http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95670

Not positive that the HF Multimeter would work, but I don't see why not. You might have to do math to find actual RPM vs indicated RPM on the HF unit (multiply or divide by 2)... I need a refresher on why tachs are selectable 1-2-3-4-6-8 cyl. In my head 1 spark = 1 rotation UNLESS you have a waste-spark system, in that case 2 spark = 1 rotation.

 

[jfoust]

Thanks for the help linksep - I'll look into that. They actually just opened a TSC about 5 miles from my house... Way better than Harbor Freight, which is about an hour or so away on the other side of Atlanta! Might have to grab a tach from there. Would be nice to have the hour meter as well!

 

[mike75925]

on a one cylinder even if lost spark type, it is still one spark per rev, two sparks per a complete cycle.

 

[Linksep]

Touche

 

[khank1995]

you should just let your kids discover what speeds to go at I remember when I had my first kart one seater with a 2.5 hp on it I was freaked out and I learned how to slow down and to go fast

 

[Kenny_McCormic]

You engine is spinning at 6800 rpm, bad idea. The throttle kit is designed to replace the gov/stock throttle linkage with a direct throttle linkage, it is a racing part.

At 3600 rpm you should be doing ~21 mph. http://www.diygokarts.com/speed-calculator.html

 

[TOO FAST]

Limiting throttle movement really takes the fun out. You do need to find out if the
engine is overevving. The only real way to slow it down is to put in a jackshaft and
reduce your ratio from 6:1 to maybe 8:1 - it'll be slower but have a lot of power which
is fun for the kids. My kids are 10 and 6 and their kart is geared to go 15 mph which is
plenty - and the power for spins, burnouts is great on a 6.5 hp briggs. Restricting throttle movement burns out clutches.