Am trying to change the fork springs on my 74 T150V and have run into a few problems. I have removed the mudguard (fender), wheel, and handle bars ok but after taking off the bottom half of the fork legs, but I cannot get further. I am trying not to remove the entire head assembly but cannot budge the locking nut on the bottom of the fork plunger nor the 'Allen' nut in the top of the fork leg (under the dust cap). Can anyone advise me - is it only the top nut I need to remove to drop the assemply out and access the springs? If so, what is the size of the Allen nut (smaller than 12mm, impirical maybe 7/16th?). Thank you kindly.