Here's another vote for the Suzuki LT-50 (earlier versions) or LT-A50 (later versions). Lots of them on the used market, parts are available at any Suzuki dealer nationwide, nearly bulletproof two-stroke engine, suspension all around, brakes front and rear, and so on. These sell used for $900-1200 (we paid $1100 for one in near-mint condition) and when they outgrow it you'll get nearly all of your money right back out of it. They hold their value really well.

The LT-A50 is rugged and dependable, which will keep your child (and thus YOU) happy. The less expensive Chinese ATV's have a long history of failing frame welds, engine problems, etc. They can be kept running but often require a lot of tinkering. Trust me, your child will NOT be happy if you have to tinker with the unit every time they want to ride it. The "savings" just aren't worth it.

I'd avoid the most recent Suzuki 50cc unit, the LT-Z50. It's a four-stroke engine which is more complicated to maintain and, from what I've heard here, rather gutless. Our LT-A50 has plenty of spunk even with the throttle restrictor tightened in quite a bit, and our son climbs all the hills around here with no problems at all.

 

There is nothing complicated to maintain on the LT-Z50 four stroke. Just put in gas (no mixing) and go. It is gutless in stock form but with only about $300 in mods (CDI, air filter, jets, and lighter CVT rollers) you can make it faster than a stock LT-A50.

 

I was in your same position just a few years ago when my oldest was turning 3. I bought him a 2003 LT-A50. -2 years later I bought my younger son a 2006 LT-Z50.
I don't know about the Chinese quads other than what I've read, but I can tell you about the Suzuki quads. The Suzuki 50's are all very good reliable ATV's which are set up to be safe, with the full floor-boards, and plastic shielding to prevent anything from getting caught or burnt. They have both front and rear brakes, and a line tether/kill for the parent to pull when teaching the rider the basic skills. The suspension on the units are O.K. for beginners to recreational riding.
Both the 2-stroke and 4-stroke versions are pretty much bullet-proof, and can be found for under $1000. used. -be patient, and don't rush into something.
The 2-stroke can later be modified by removing the factory restrictors, air-filter mods, and jetting. (many helpful threads on these)
The 4 stroke can be modified for more power, but will cost a couple hundred $$$, find out by searching the Suzuki Forium under "ltz50 quad no power"
With a 4 year old rider you shouldn't need to make any performance mods for about 6 months or so depending on how quick he catches on, and how much /often he rides.
Bottom line, you can't go wrong with the Suzuki's. I have both, and for a 3 year old, they are perfect. As the rider gets the need to go faster, they can be adjusted/moded to go faster. I've never had a problem with either model, and they are extremely reliable quads.
The time goes by so fast... My oldest is now 6 years old, and throws the 50 around like he owns it. Even with all the mods eventually they'll outgrow a 50, so I'd suggest that you try and get something that you will spend more time watching your child riding and having fun, and less time wrenching.

 

Thanks everyone! Your advice will go a long way. I will keep my eyes open for a used Suzuki or other brand name quad. Unfortunately, I don't see many around here (coastal NC). I supposed he doesn't necessarily need it on his birthday so I can take some time to look around. Besides, he has a younger sister who will inherit it eventually.
Thanks again!

 

glad we can help. look at ebay, craigs list. or if you have a little time save your pennies and go to a dealer. get new