Just Got my 5yr old an ATV but had to mod the brake handle to fit his hand. I posted some pics on my page. I just took a handle from a cabnit and connected it with a couple of pipe clamps.

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2005 eiger
27in Mud Lites
2.5 Warn Winch

We use a large zip tie between the brake lever and the mount. Cheap and easy.

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1999 Polaris Sport 400
2001 Polaris Trailblazer 250
2001 Polaris Scrambler 90
2003 Suzuki LT50a

I did mine a little different.You still use the stock lever it just brings it in closer to the bar...Pics are on my page as well.

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Happy Trails
2001 Yamaha Warrior
2004 E-ton Viper 90
2007 Arctic cat 700 EFI

<insert many headshakes> Guys, I do not like to criticize... they are your kids... Please make sure they are dressed safely... But I can't let this go. The fact that your child's hands are not not capable of working the levers should be a flag. I can only say to you to be very vigilant, and make sure the riding area is clear of hazards. Don't get me wrong here, I did the same thing with my youngest when he was 6. He scared the you know what out of himself. And now he is 12 and only now is ready to try it again. I hope your experience is better than ours.

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Lets just say these old bones have buckets of experience...
Yamaha Warrior
Yamaha Blaster
Yamaha Raptor 660
Yamaha Raptor 80
Honda Rubicon
Yamaha 450 IRS 4x4

Thanks for the concern, I have the throttle toned down to where his power wheel jeep goes faster. He has been riding with me and my wife on ours for about a year so he knows how the gas and the brakes work. The only place i let him ride his new one is in an open field with my finger on the kill switch.

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2005 eiger
27in Mud Lites
2.5 Warn Winch

Most of the mini's seem to have adult sized levers for some reason..It's not that the kids are necessarily too small its that the levers are just too big for what is supposed to be an atv for children...My son could always use the brakes but this modification made it easier..The back brake still has the unmodified brake lever but since its hydraulic it takes much less force to use..

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Happy Trails
2001 Yamaha Warrior
2004 E-ton Viper 90
2007 Arctic cat 700 EFI

Well it sounds like both of you have thought this through then. It is hard to judge ablility from a computer thread. The unfortunate thing though is many parents do not. I am all about family time together. You might try and convert over to one of the MX levers I see that have more of a dog leg in them that supposedly gives them more leverage, and may fit smaller hands better.
I am a believer like yourselves that 6 is a good age to start, but after spending two years researching the injury stats, I have come to the conclusion that barring downright stupid decisions on the part of parents like putting them on a full sized machine etc, statisitically a child that young is at high risk. The issue isn't so much the ability to hit the throttle, work the brakes etc, it comes down to concentration levels, and ability to react in dangerous situations. I am glad to hear you are closely monitoring them, and are right there to assist. I suggest you look at using radio communications so you child can also hear a reasuring voice of an adult in their ear when they are faced with decisions they may not know how to handle. Chatterbox comes to mind, and makes a good teaching tool. I also recommend a riding area that goes in one direction, where your child will not be faced with oncoming traffic on the trail.
I know it may be too late now, but consider a small dirt bike as an alternative. The hand-eye coordination needed is the same, however the bike is much lighter, and less likely to injure in a fall. Reason being, in a crash scenario, the body and machine tend to take different paths in a dirt bike shunt, however with ATV's they tend to take the same path, with the ATV coming out on top each and every time. Please consider widening them by using adapters etc. That will make the machine very hard to roll over, and handle like a spider.
Lastly, pay close attention to their attention span. In a child that young, it is pretty short. When their attention wanders, it is time ot get off the machine and do something else for a while. Kids need stimulus... and ever changing action. It is OK for them to ride for 10 minutes then want to go play with their hotwheels or throw rocks at a toad... These are special moments to be cherished as a parent. Enjoy them while you can.

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Lets just say these old bones have buckets of experience...
Yamaha Warrior
Yamaha Blaster
Yamaha Raptor 660
Yamaha Raptor 80
Honda Rubicon
Yamaha 450 IRS 4x4

I also had another thought... what is up with these MX style boots? They are so rigid that kids have a hard time shifting gears and using the foot brake. Let alone watching them moon walk in them. I sure wish someone would make a boot that poffers some armor, but more importantly give them the ability to flex so the natural foot action is maintained.

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Lets just say these old bones have buckets of experience...
Yamaha Warrior
Yamaha Blaster
Yamaha Raptor 660
Yamaha Raptor 80
Honda Rubicon
Yamaha 450 IRS 4x4

I had on old pair of MX boots that had a "hinge" at the ankle that would allow very easy up and down motion of your foot...I don't know what kind they were but I don't see any made like it today...Luckily my son's viper has no gear shift or foot brake so its not a concern but yes a little more flexible boot would be great.

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Happy Trails
2001 Yamaha Warrior
2004 E-ton Viper 90
2007 Arctic cat 700 EFI

The boots need to be broken in. Try making them were the boots wet and walk around in them. Old army trick. Also, make sure you condition the leather on them.That also helps.

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2006 DVX400
2003 LTZ400
2007 KAWASAKI KFX50
2005 RAPTOR 350(GONE)

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