My son and I kart. He races at a series one of our local track has. We currently have a mid 2000's Birell with a KPV-3. Also have a Margay with a Briggs world formula that I drive. The 4 stroke stuff is great due to the ease for use.. pump gas, pull start etc. The KPV on the other kart requires a start box, outside of that, it wins hands down. A reasonable upgrade is the KA100 package from Iame, good power and electric start ( as known TAG). Let me dig up some pictures.