Hi John..You might have to shorten the push rod..but before you do that check to see if you can adjust it by backing off the screw in the clutch operating arm at the gearbox cover end.
If that won't do it you will then have to shorten the rod.
There is no specific measurement for this..
So, soften one end of the pushrod by heating to red and allowing it to cool naturally.
You won't have to take off very much..I would start by taking off approx 1/16" and then trying it, cutting off more in small increments and retrying it until you get it right. Remember that when the handlebar lever is fully pulled in the operating arm should be vertical after adjustment. Use the screw in the operating arm to make adjustments and then alter the cable settings to suit..don't use the cable to make any adjustments. Also check that you have some free play at the pushrod/operating arm end after you have adjusted the cable.
Reharden the rod by heating to red and quenching immediately in cold water.
After hardening you will have to temper it back as it will be too hard.
Clean off the end for the last 1" or so of the rod with emery until you have a bright finish.
Put the rod in a low flame and let it come gradually up to temperature. As the temperature rises the rod will change colour...first a pale yellow (straw) then a darker yellow then brown etc.
Just as the rod starts to darken from the pale yellow, quickly quench again in cold water.
Don't worry if you go too dark...you just repeat the hardening and tempering process again from the beginning....Ian
email (option): ian@wright52.plus.com