I fixed my scooter's surging problem, but I have no clue why the fix worked!

[AgilityOnAnRV]

After doing and testing everything on the planet in hopes of solving the problem of my scooter surging / lurching around 50 mph I finally decided to try (re)replacing my new carb diaphragm with the old one. Voila, problem solved. I just cruised down a frontage road at 60 mph with no sign of surging.

I'm glad that the problem is solved, but what the heck? Can anyone explain?

Thanks!

[AgilityOnAnRV]

Oh, and this totally makes me think that some shops have no clue what they're doing. I was just at the point where I was going to turn over diagnostics to a shop and when I spoke with someone just yesterday they said that it's definitely in need of a carb cleaning and that it would be around $130.

Yeah, that would have helped... empty my wallet.