whats the biggest engne you can fit on a 1999 sportster?? 96 CI????

 

Chris, S&S 100 inch engine has the same cylinder length and will bolt right in. 88" is about the biggest I would want to take out of stock cases. Built a couple of those, on with the Revolution kit and one with Axtell's kit. Both made 120 ponies. Fun if ya like the frot end in the air.