Front Axles

What's the Difference?

by Alan Buehner

Originally printed in the 2008 issue #41 of Still….Keeping Track

The Penton motorcycles came equipped with Cerianni forks from 1968 thru 1976, after which they were equipped with Marzocchi forks.

The front axles used on these all look the same. They are fat on one end then taper down to slide through the wheel hubs. Looks are deceiving because the different sizes of forks used different lengths of axles. The purpose of this article is to show and identify the various axles.

Each axle shown is identified with the Penton/ KTM part number followed by the years, size, and brand of forks used and the measurements.

Refer to the POG "Tech Tips, What's the Difference? Front Forks" article in the Spring 2004 issue no. 22 newsletter. This shows and explains the different front forks used on the Penton/ Ktm motorcycles.

A. #6-35-000 front axle used on all the 1968-71 Penton motorcycles using the 35mm (short) Cerianni forks. The over-all length is 1 O" (255mm) with the thinnest part of the shaft being 7-1/8" (183mm) long.

B. #51-09-081-100 front axle used only on the early 1972 bikes equipped with the (baby) 32mm Cerianni forks. These forks have narrow fork plates that measure 6- 1/4" center to center for the fork tubes. The over-all length is 9-1/4" (235mm) with the thinnest part of the shaft being 6-3/4" (173mm) long.

C. #52-09-081-100 front axle used on the 1973-73 bikes equipped with the 32mm Cerianni forks (measuring 6-3/4" center to center on the fork tubes) and the 1973-76 bikes equipped with the 35mm Cerianni forks. The over-all length is 9-3/4" (248mm) with the thinnest part of the shaft being 7-1/4" (185mm) long.

D. #55-09-081-000 front axle used on the 1976-78 MC-5 and 1977-78 GS-6 bikes equipped with the 35mm Marzocchi forks. The over-all length is 10-1/2" (270mm) with the thinnest part of the shaft being 7-1/2" (193mm) long.

E. #55-09-081-100 front axle used on the 1979 KTM MC-80 bikes equipped with the 35 & 38mm Marzocchi PA ZTI A/S forks. The over-all length is 10-3/4" (270mm) with the thinnest part of the shaft being 7" (177mm) long.