Stock '10 Ultra Limited 103 CID, 70 HP, 85# TQ. Stock '10 Sportster XR1200 74 CID, 90 HP, 74 # TQ.

I just don't get why the Sportster EVO motor gets so much more stock HP than the much larger and more "advanced" (?) TC motor in the big bikes and still manages to pass EPA requirements.

 

look up your math to compute HP, now look up the rpm each motor is making said hp....

 

The XR1200 Sportster engine will rev MUCH higher than the Big Twin engine will ever be able to because of less reciprocating mass. The Sportster engine has smaller pistons and smaller valves compared to the Big Twin engines. All the Sportster engines have four cams, one for each valve and the engine was designed to be a RACE engine from the start. The XR1200 is the very latest in a long history of RACING Sportster engines and would get even more horsepower if the air intake was larger, like on the Buell motorcycles and it has special oiling to help cool the pistons down as less heat equals more horsepower. I hope that this information will help you to understand. Take care and ride safe out there! Sportsters Rule!

 

OK, I guess that's what's up with the differences.

Thanks for the help, I appreciate it.

John