74 - 250 Shift Drum

[KJDonovan]

I picked up an early 74 250 (4-5402696) basket case some time back and I am in the process of resurrecting it.  I came across something this weekend that left me scratching my head, so I thought I would see if anyone can shed any light on this.  

For starters when I picked this up, it was a true basket case, engine was completely torn down in a few boxes.  Based on what was in there, it appeared this was a 74 250, but came from the factory with 14MM kicker shaft which shattered sometime early in its life.  Anyway, I replaced the shattered shaft with a 17MM shaft.  So a friend and I were pulling together the bottom end and just could not get it to shift right at the bench, so after a few tries without success we tear it down again and start looking at the shift drum comparing it to some earlier (72) shift drums I had.  I know the earlier shift control drums are essentially male and engage cuts in the shifter forks and the newer ones are female that engage pins on the shifter forks.  

Here's what I don't get.  On the earlier KTM shifter drums there were 7 detents to engage the locating lever.  7 adding up to 6 speeds and neutral, so there is no wrong way to install the shift drum.  Just drop in the 2 shafts with the gears and forks, then the drum and it all works fine.

On the shift drum I have with this bike there are 8 detents which for a 6sp bike implies a particular orientation during assembly in order for the bike to shift properly.  I scoured all the documentation I have and I can't find anything regarding the orientation of the shift drum during assembly.  

After some trial and error it is now shifting properly at the bench, but now I am wondering if the shift drum that was in the basket, is correct for the bike or something the PO just tossed in.  

In looking at my parts manual (page 34 II) the detent area of the shifter drum depicted there does not resemble this one.  Below is a picture of the shift drum and the area indicated by the red arrow is where the locating lever engages when it is in first gear.  It seems to go through all the gears fine but if anyone has any ideas on this it would be appreciated.

Thanks,

Kevin

[Richard]

I don't know exactly when the MC-5 motors reverted back to all six gears being able to be selected, but my early MC-5 came as a 5 speed. All six gears were there, but you couldn't select first gear. The pin in the shifter drum was not installed. So, my drum has the eight detents also. Six for the six speeds, and two neutrals. One between first and second, and one between second and third.

[ALB]

Kevin,

In checking my new old stock inventory, the shift drums that I have all have the 8 v-cuts, just like yours.
The drums are for all the KTM silver engines. They are all six speed with one of the pins cut out to deactivate 1st gear for the 5 speed MC5 engines.
The early black KTM engines (1972-73) came with shift CAMS. There are only 7 V-cuts on these. They are all 6 speed. These shift cams could also be in the early 1974 engines as KTM was known to use up all excess inventory before installing new/ revised components.

Alan Buehner

[KJDonovan]

Richard / Al,

Thanks for the information.  So with this being case, i.e.  All the 74+ (Non MC5) 250's used the same shift drum in 6sp bikes.  I would assume that this means that at time of assembly, the drum needs to be indexed to a particular starting point, given that unlike the earlier CAM drums it cannot find its own way.  So my question is, what is the correct starting point?  Is it just a trial error like I did or something else?

Thanks,
Kevin