2012 ST 2+2 safe speed for engine?

[PeterBott]

So I got my new 2012 ST 2+2 with a kawasaki 401cc (13hp) engine today. The guys at the shop said they could make an adjustment from the factory setting to make it faster, so of course I said to do it! I tested it on the street last night with GPS and it was doing 28mph with 23" tires. I have since read that it may not be good for the engine parts if the engine is run too fast. I think they just adjusted the throttle linkage or something but I'm not sure. Is this too fast and am I going to damage the engine? I like it being fast but definitely dont want to hurt the cart. anyone have thoughts on this? Does anyone have an idea what they did? it only took a couple minutes.