Straight from Novarossi is their newest engine; the Plus 21-5K and KT (turbo version). The engine is the successor to the massively popular Plus 21-5 engine.
The differences with the 5K are, a P5 sleeve, updated crankcase with 7 ports. The engine serves as a tribute to Novarossi’s P5 series; but eclipsing the P5 with more power, and better performance!
More info @ Novarossi