As written in our parts dept
http://www.mecoa.com/kb/parts.htm
Sportster engine family consists of 3 sub families. The .20 & .28, the .45, and the .65
Complete History for .20 & .28 .45 .65
Distinguishing features: 4 bolt head, Made in USA on one side of case, K&B (not oval logo) on other side. Some had size stamped on mounting lug but most had no size reference. Plain bearing engine. You can determine the size by counting the cylinder fins... the .20 & .28 have 9 fins, the .45 has 10 fins, and the .65 has 13 - Click on "Model No." to see picture.
you have a Sportster 65