Kt 100 talk

Well if you want to look at numbers to see the comparison to an open, we can look at power to weight ratio (HP/Weight). Lets say we have one go kart with a Sudam 131 that makes 50HP, which means by UAS rules it has to weight 235lbs + 131lbs = 366lbs. This means:

50HP/366lbs= .137HP/lb

So for a yamaha to get the same power to weight ratio it would have to weigh 190lbs (assuming it makes about 26HP). Now I'm not sure about you guys, but I couldn't get a go kart to weigh 190lbs with me in it. Now lets say we have a modified yamaha that makes 35HP, it would still have to weigh 263 lbs.

Now this would all change when you look at the tires load sensitivity, but thats another subject. These numbers are would only be completely reverent if we ignore most of physics. That being said, it is still a very good reference when you are looking at motor choices.
Big problem with any engine making that kind of H.P. is that the more H.P. , the less, reliability, then you need to look at comparative rods and ign. systems.