what suzuki does with their jr50 to control speed is to put a washer in the exhaust between the header pipe and the exhaust port. this would work and be an easy and cheap way to control speed on your atv's, you could also make a plate with a smaller hole between the intake manifold and cylinder would to do the same

 

You could also install a spacer on the variator boss if it has a cvt trans.

 

Gearing is you best option.
It will give them more power for uneven terrain and is easier on the clutch but also limit their speeds.
reducing HP to limit sppeds is just harder on everything and takes the fun out of riding

 

It doesnt have a variator like that. I wouldnt show them how to use the throttle screw. Or I'd kick their little azzes if they messed with it.

 

The one thing I am running into with my sons is when I get the screw where I want it on level flat ground it wont have the speed/Power when we go on rough terrain and I have to adjust it to be able to perform. I also have trouble keeping it from falling out. With enough vibration it falls out and I cant locktite it cause I have to keep adjusting it to where we are riding. I see alot of ideas with the screw but can you explain a little more about the other ideas on this

 

Im gonna comment just because hudie01 revived this. DBCC , get your crap together!!! Are you a dad or what???????????? Fastestdad, two thumbs up!!! I would whip their butts in a heartbeat. Your the boss ,not them. If they can't obey,then get rid of the bikes. Its that simple.

 

i think the throttle limiter screw is a joke aswell and felt my son who is 9 needs the full power of all 90cc's SOMETIMES, like in the deeper mud,and on the hills but the best speed restrictor made /and works on all atv's is YOU the parent!! like i said my son is 9 and i don't let him go rippin around all by himself, when he rides he's riding with me , usually with me in front dictating the speed and trails we take. when he does get to run laps on the kids track i'm standing right there watching and he knows what his limits are and what i'll let him get away. all because we set rules when he started riding and supervise his riding

if you do the same the limit screws will never be an issue

if that dosen't work i'm with the last too ... and whip dat azz

 

OK it is settled. I am going home to beat my kid and throw the damn screw away. lolol I am just kidding. I totally agree with you guys. My only fear with the screw is more panic throttle then him not obeying my rules. I appreciate the input because for us who are totally green to all of this is, it helps a lot.

 

Just slap him in the back of the head so the bruises dont show. LOL

 

I considered this exact problem when we bought our son an LT-A50. Fortunately the intake restrictor and throttle screw have worked out fine... he's limited to about 15 MPH but can climb nearly any hill we encounter (and some are pretty steep).

But if that had not worked, I was thinking about a *speed* based limiter as opposed to an engine power based limiter. And that means you need some way to know the speed of the machine. These little quads don't usually come with a speedometer, so the first job would be a speed sensor - perhaps a Hall effect sensor on the rear axle. Then you just need a frequency comparator to know when to cut out the relay that controls the spark. That could be adjusted by a trimpot as the rider's skills improve.

One problem for us on the LT-A50 is that it doesn't have an electrical system nor battery. There's no source of constant DC on the machine. There are a few solutions to that but they're not convenient.