These WR engines are rare. The only way to buy one was through a dealer(of coarse) and you had to have a racing license. Class C via AMA, American Motorcycle Association
This is a 1950.
Special features (different from standard WL/45" engines include:
Sprocket Shaft (special for ball bearing)
Pinion Shaft w/oil groove (special for ball bearing)
Crank Pin (special size for WR rollers)
Drilled Connecting Rods
Special Lightened Flywheels
Special Cams (for WR only)
Special Ball Bearing Idler Gear and Spacer
Special Gear Cover for Ball Bearings and Wico
Ball bearings on #3 and #4 cams(both ends)
Ball bearings on #1 and #2 cams (case end only)
Special Angled Tappet Blocks
Flat Show Angled Tappets
Special Tappet Covers
Right Case (special casting for magneto idler gear stud)
Left and Right Case with special machining for Ball Bearings
Right Case machined and drilled for Wico/Edison Magneto
Special Cast Iron Cylinders with larger cooling fins, larger valves,
smoothed ports, and special valve angles...
Special Pop-Up Pistons (same as K, KH, KR)
Special Valve Springs
Special Cylinder Heads and Combustion Chamber
No Head Gaskets !
...and it all must be hand-fitted, must spin free, no binding with correct race
clearances and tolerances for high speed race situations...