The brother wants to ditch the Lefty fork in his about 03 Jekyll. What can go in? Can’t work out if there is a normal fork out there with a matching headset size or if he needs to sleeve it down to fit something. I suspect it’s inch and a half but am not sure. Any ideas? Any other issues? Anyone want a to p/ex a cheap Lefty for something with 2 legs?

An 03 lefty will be very tired, unless given reasonably regular servicing, wouldn’t expect to get lots for it(I might well be wrong).
You’ll need a new headset for the frame, as the headset is specific to the 1.56″ lefty steerer (not the newer “onepointfive” std) – remove it and sell with the lefty.
I assume you’ll be looking for something around 130/140mm with an axle, in order to match the lefty. I won’t suggest anything specific, but you can fit a fork with any steerer type (std 1+1/8, tapered or 1.5) with the right headset.

How much would you want for it?

TBH unless he’s lots of spare cash for the headset, fork, stem & new wheel (it all add’s up). Maybe just get it serviced? What doesn’t he like about it?

It needs servicing every 5 minutes and he wants something that needs servicing every 5 years if it gets a hard life. The alternative is a new bike. It’s going.
I’ll post it here when he decides what to do.

So a 1.5″ headset is what he needs or something to sleeve that frame from 1.5 to whatever?
Ta.

If he wants a fork that needs servicing every 5 years he’ll have to get a rigid one! All sus forks need regular servicing.

A headset is required that fits 1.5 steerer, dependant on fork, you need a headset with a reducer. No sleeve required or even available.. As above, all forks require some regular servicing, some servicing can be done at home, but all have some jobs that need a specialist at some point (eg: bushings)