I asked if it ran and he said it would with new ignition parts. I had the family waiting outside in the car for awhile while we looked at the 750 and made a test cut and didn't have time to get into the 550. Any idea how hard it is to find parts?
The pro series ignition parts are popping up all the time for sale on feebay. It may be a simple fix, so could end up just taking a little time. Not sure how much you know about these ignitions, so if I say something obvious its because I'll assume for other readers some details are needed.
All the pro series (350/360,450, 550, 650, and 750) use pretty much the same ignition system. I say "pretty much" because there are differences such as 450s using a blue trigger module that has a rev limiter, and there's other little details I won't bore you with here. All the saws have a trigger module that is mounted next to the flywheel and a transformer or coil that bolts over the end of the spark plug.
I've laid hands on dozens of the '50 saws and the only ignition failures ever seen were due to a failed contact somewhere in the system. Two problems that have popped up more than once are where the transformer mount contacts the rear cylinder shield for ground, and the coil spring inside the transformer that contacts with the spark plug. The first problem just needs a good cleaning to fix. For the second problem, I've seen cases where the spring had been overly compressed, covered in gunk, and times where the spring had broken. If its broke, you may could solder, but may need a replacement, otherwise its an easy fix. There's always the possibility of a shorted kill switch that could cause a problem, but I've never seen this on a '50 saw.
There's posts on here at AS about how to troubleshoot these systems, so I won't repeat. You can google and hunt for "homelite 750 ignition site:arboristsite.com" and find more than one post that'll hopefully answer any question. Bottom line is the transformer is easy to test and the trigger module pretty much needs testing by parts swapping. Anyways, don't be scared of ignitions for these saws, just go get that 550, 'cause you'll love it.
Dan