Is it twin carbed or single? The single carbed Z440 was pretty much a jazzed up Jag, still a good, bulletproof motor, but the second carb really woke up that sled. I had a buddy with a twin carbed Z440 when I was primarily riding my '97 Jag, and he could have his way with me any time he wanted. Another friend had a single carbed Z 440 and he and I were about even. Those cat 440s just won't die, I'm actually picking up an '89 Jag AFS today. They have some power, but aren't going to rip your son's arms off. I started on a '93 Jag 440 in '95 when I was 8...so I'm sure your son can handle a little bit more power at 11. go for it, you'll like it!