Do I need a lawyer for a car accident when fault is disputed?

Laying this out as a comparison because the disputed fault part changes the whole calculation. Riding my motorcycle, a car turned left across me at an intersection, and now their insurer is pushing this line that I "must have been speeding," which I wasn't. Clearish crash, except they're trying to make it mine. So do I need a lawyer for a car accident where liability is actually being fought, or can I handle the fault argument myself?

Solo, the appeal is no fee, and if fault were clean I'd probably try it. The problem is that in Pennsylvania any slice of blame they pin on me comes straight out of my recovery, and past a certain share I get nothing at all. So the speeding line isn't them being annoying, it's them trying to assign me a fault percentage to shrink the check, and I'm not equipped to fight that against an adjuster who does it for a living.

With a lawyer, the trade is the contingency cut, but the job becomes rebuilding the fault picture, the turn, the sightlines, witnesses, any camera, and pushing the speed story back off me. On a disputed fault motorcycle case that rebuild is most of the value.

So my read is disputed fault flips this from a maybe into a probably, where a clean minor crash might not. Riders who've gotten the "you were going too fast" treatment, did fighting it solo ever actually work?