74 vs 75 suspension

[ksithumper]

Unfortunately there is no suitable  UK race class for my '75 KTM 400, unless I go in with the 12inch travel bikes. (the former pre-77 class died thru' lack of entries).

I would be able to ride in the pre-75 class, assuming I convert the rear to '74 spec.

From the photos I have, the '74 bikes have the same frame and swing arm, only a more upright shock position - it looks like the 75 has both shock positions already in place?

Is this right? What length shock do I need to be a '74 guy?

[tomale]

Welcome, yes you are right, the frame is the same, I believe you will need 13& 1/2 inch shocks, but it sort of depends on how you want to set up the bike. using a little longer set of shocks will change the fork angle and make it corner a bit better but it will loose high speed stability. The other thing you might have to do is add shim in the front forks to limit the travel. Here in the states this bike is legal for vintage class but only if you limit the travel to 7 inche in the front and 4 inches in the back, I believe in stock trim, the front has a little more than that. I think we make too much of all of this but that is another topic altogether, The real change did not appear until 76. My 76 MC5 250 has 9 inches of travel in front and a bit more in the back. Hope this helps

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
75' GS400 (project bike)
72'sixday (project bike)