Question; When you find that grail bike, like perhaps a pre 80's PX-10 that's had a few parts replaced...........whereas someone has jackscrewed a nice pair of Japanese pedals into the French threaded crank arms, are the cranks ruined for the sake of originality?

Eh, pedal threads. Doesn't bother me as far as originality. More practical if they are 9/16".
I would have them tapped to make the threads
consistent and sharp.

plus many pedals (both French and a few Japanese brands) were available in both threadings...so who would know unless/until you told them or they pulled them off for servicing?

It's also possible to repair "by the book", using special threaded inserts. These require a special tapping tool which isn't cheap, as well as a reasonable amount of expertise.

Yes they are but I wouldn't be concerned about it. I did it to a Stronglight 93 crankset so I could use "standard" pedals. If I was anal about it, I would find replacements and save up for French threaded pedals!

I have french pedals with 9/16" threads screwed into a 9/16" threaded stronglight on my 60s px-10. Mind you I also tapped the rear derailleur mount so I could put a shimano crane on there so I'm probably the wrong fella to be asking about originality.

Tap the cranks properly to 9/16" x 20 and obtain the French pedals that look correct with the matching revised threading.
There are no concours judges to mark you down.

If its an 80's PX10 the cranks were probably 9/16-20 from the get go. Most of my early 70's PX10's came from the factory with 9/16-20 Stronglight cranks.

I must confess, I have jackscrewed my share of threads before I knew any better. That said, I have recently come into a couple of french threaded bicycles, both from an era when mostly clamp on cable guides were being used. While I could find a French branded pedal with a JIS thread for my buggered up French threaded cranks, BUT, when that bike comes into someone's hands down the road.........okay, not such a big deal I guess. However, if I were to pick up said crankset at a swap meet or if I bought them on ebay I would feel somewhat jilted..........sorry, just thinking "out loud"

Bikes trashed, its been rendered worthless, send it to me for proper disposal....

Your just fine, ride and enjoy your px10

It's an early 70's PX-10.............the NDS spun out rather stiff while the DS spun out what I would call normal.

By the location of the decals it's a pre 1974..........I thought these were french threaded?

PX10 crank pedal thread size is stamped into the backside. You'd think they'd all be French thread but surprisingly they're not.

Yes, your originality has been jackscrewed and you are now a free man! Mumble a few words of thanks to the deity of your choice and carry on.

Ahhh..........Indeed they are French. Stronglight Crank arms are marked 14 X 1.25 and the Kyukuto Pro Vic II's are marked 14R and 14L

I feel much better now..........

They should have used D(roit) & G(auche) on French-threaded pedals.