My son has a 03 suzuki lt 50 were looking at either trying to get more power out of this quad so he can race or upgrading I found a good deal on a Baja 90 are these any good I have only ever had name brand atvs don't have any experience with any of these other brands would this be a good start to build a lil race bike or should we build the 50 or buy a different brand thanks for any info

 

Welcome to the forums.
A LT50 is never going to be a race quad.
As far as the baja 90, it's a 2 stroke with plenty of aftermarket parts to be had.
What you need to do is figure out what quad he fits properly on. Sounds like a DRR/Apex 50 could be more in line.
atvsafetyinstitute.com or the ATVA website lists the recomendations. Basically:: sitting on the seat with feet on the pegs and knees bent. Fingers can reach and use all the controls.
Be warned. Racing isn't cheap. Even local races , the minis can have 4-10K in them in a heart beat.