Horsepower and torque. These two things are desired by Harley-Davidson owners, and most will go to elaborate means to achieve what they want. When H-D introduced the 120R, it was only a matter of time before aftermarket manufacturers developed parts to make The Motor Company’s biggest motor even bigger.
After we sent our bottom end to the guys at Darkhorse Crankworks, it only seemed fitting to reassemble the motor as a 124-inch beast. To do this, we contacted TR Reiser of T-Man Performance and went over the details of the build. TR informed me that he has developed a 124-inch upgrade kit for the 120R crate motor using Nikasil cylinder technology as well as a new piston ring design. The kit is a bolt-on and requires no case boring. After we got some specs from TR and passed the info along to Darkhorse and Dave Mackie, the two were able to set up our heads and the crank accordingly and get the bottom end on its way back to the shop. TR sent us the piston and cylinder kit. We had the 120R heads worked over by Mackie, whose porting skills and finishing work are second to none. When we had received all the parts back it was time to get to work building a 124-inch monster.
Sources Darkhorse Crankworks darkhorsecrankworks.com
Dave Mackie Engineering davemackie.com
JIMS USA jimsusa.com
San Diego Customs sandiegocustoms.com
T-Man Performance tmanperformance.com