crf50,ttr50,kfx90,kfx80,lt80,drz70,klx110,drz70,predator 90,ds90x,ltz90,kfx50,trx90..........all those small kids bikes/pitbikes/small atv are what you should be looking out for
get him an lt 80 i had one wen i was 4 till 9 and then i sold it and got a dirt bike then a blaster the lt 80s are just like the blasters oil injection but they are more reliable than a blaster
lt 80s are the shizzel there two stroke and you cant go wrong they got governors on them also so you can adjust the speed that you think your kid wont crash at
my litle brother has an lt80. they are great little quads. they also have great resale value. he always gets mad at me wen i tell him im selling it to get myself more parts. he loves it