Two years ago, I got my kids a 2006 Polaris 120 Dragon. My brother got his kids (the same sled lol) a 2005 Polaris 120 Pro-x. This is a fun head to head that you guys with 120's might find interesting that will give your kids 120 a little added power. My 120 ran like poop, started hard, stalled a lot and ran slow. So...I came across this website called recmotor.com and in attempt to get this sled running better I purchased this:
POLARIS XC/XCR 120 POWER INTAKE KIT
Best performance Gain for your Dollar
Our kits include a special preload and rate governor spring to let
the 120 rev higher without damaging its plastic governor like solid
wires can do. The new style spring will also give you a smoother
idle without surging, like running with the governor unhooked will
cause. Next we developed and flowbench tested a new velocity
stack that will let your engine have better throttle response and
top end rpms.
To top off the POWER INTAKE KITS, we built an adjustable
main jet so you can set your carb for peak performance at any temp.
The best performance gain is achieved when you use our complete
kit, but parts can be purchased separately.
Part #: PI- POL
Price: $97.15
Now they offer a boat load of performance products to make a 120 faster but my daughter is only 5yrs old so I was only mainly looking to improve or make the sled run better. I got the oil changed, added new non-ethanol gas and installed the kit.
The results were incredible. Just by the naked eye (and ears) the sled ran faster and sounded better/faster. So...we lined them up. 'I' (all 225lbs of me) was on my daughters (modded 120..lol) and my brother kid (50lbs) was on his stock 120. The kid got the hole shot (I am sure because of the weight dif) but by 10-20ft I blew right by him

like he was sitting still. No joke, that kit certainly is as good as advertised and did the trick. The mph gain had to be at least 5mph! Remember...I (225lbs) was on the 120.
If you are looking for a little extra added power for your kids 120 this is the kit. I give this product two

up!