I have spent the money and repaired my saw. Only because I found out my cousin has a new job at a garden machinery spares place. £17 for a new starter recoil spring and drive pulley.
Put them on on Sunday tea time. Pulled the starter handle and snapped the starter rope. Grrrrrrr! Too late to get a replacement. Picked one up on Wednesday. Started first pull. Then had a good tune up without the bar and chain on. YouTube and some old manuals downloaded from the Internet helped no end. Sneaky trick to starting was to squeeze the throttle and the wedge your foot under it in the handle / guard.
When it was all in bits I found the reason why I was having trouble with the chain tension. What I thought was a captive stud for the bar and lock nuts was in fact a long cap head bolt that’s only accessible with the starter coil cover removed. Allen key up the recess, nip the lock nut up, tension the chain, then lock everything down.
A couple of runs of the chain, check, Ok, small cut, still OK, cut up a big log, still spot on.
I AM MAN!!!!!!’
Guess whose neighbours will be annoyed on Friday?