Changing gearing on Raleigh Sprint

[west coast worker]

Thanks. Freewheel range is 14-26 and chainrings are 52/42 (must have miscounted before!)
I'd like a bigger big cog on the back of course, but I'd also like a smaller one for more top end speed, and I have a feeling that's not going to be possible with a 5 speed (I don't think the Sachs Huret rear derailleur would cope with a 6 or 7 speed, but I guess I could fit a new one, I did up my old Puegeot from 5 to 7 speed, that ended up as 14-28 plus a compact on the front, but it was too much of a stretch to be honest, I'd be happier with 6 speed).

 

[west coast worker]

Thanks to everyone for the friendly advice.
I have decided to experiment with fitting a new freewheel block, looking at a 13-32T, which will give me theoretically both more speed top end plus significantly lower gearing for hill climbing, albeit some biggish step changes. I'll let you know how it goes.