I'd say around 40-50% of the length of the adjustment screw. It can be a trial-n-error thing. Take off a bit and try it. Keep shortening the rod to achieve enough free-space to allow threading the adjustment screw solidly into the plate and allow enough range on the screw to allow adjustment.

The ends of the rod are heat treated for a reason, but I've modified a few and never have had an issue. Just "shape" the end of the rod to seat properly against the adjusting screw. If it's not perfect...it will seat itself thru wear. May require a few adjustments while this is happening.

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EDIT:
Be sure you have the rod all the way in against the lifting mechanism B4 you start cutting anything.

 

The "lifting" mechanism is the ball and ramp correct?

 

Correct. If the ramp has been pulled forward out of it's seat, there's nothing to push it into it's seated position. Just push on the rod from the clutch-side with a screwdriver (or whatever) and make sure things are seated. The clutch lever should be in the "home" position...all way out against the perch. Only mention this because if the ramp is not seated, you may wind-up whacking too much off the rod.

 

Ok thanks I will give it a try tonight

 

Well, I cut the mainshaft just under 1/2" and put it back in. Now im tackling getting the ball and ramp to move once the kicker cover is installed. So Im grinding a little at a time on the cover for the ball and ramp to move free. Slow process

 

Thanks 0734, it was a trial and error type deal. But I finally got it working good, here is a pic of the kicker on my 92 Springer. Its a little dirty from riding in the rain yesterday