Jackshaft Assy. – Big Block – The Burris 520BB series 4 cycle jackshaft unit for the “Big Block” Honda GX390 and Briggs 305 type engines allows for an extremely broad range of gearing and installation options. If you are in need of a low gear ratio for short tracks, the jackshaft unit will allow you to use clutch drivers that still utilize the bearing (14T +) and rear sprockets that allow for ground clearance, yet still get ratios about as low as you would want to go.

The Big Block type unit is only available as a rear mounted unit and single side where the drive remains as an inside drive.

Using a Burris chassis plate (not included) allows the engine to be moved to the right to get more clearance between the clutch and seat or seat strut. You must purchase a Burris chassis plate if you do not already have one.

5 degree = BMC 592 (American) or BMC 593 (International)

15 degree = 540 (American) or 541 (International)

SE type – The SE (single end) type retains the inside drive location of the rear sprocket. Used for arena and short track oval racing that require low final drive ratios.

Make sure to select the proper options when ordering (block location, gear sets and shaft type)

Typical Karting applications will utilize the 24T primary gear with the 28T primary being more likely for Quarter Midgets applications.

Gear Ratio Calculator

Click on the link above for the interactive gear ratio chart: