A different flat spot mystery solved

[65swb45]

I recently got a carburetor in for rebuilding with a note from the customer saying that it had a flat spot after the last shop worked on it. Now those of us who've fussed with carbs for any amount of time know that there are many, many reasons why something else is wrong with the engine that makes the carburetor the victim, not the culprit.
As Im taking the carburetor apart, I can see that it's a decent rebuild. Not great, but decent. As I get to the end of the disassembly, I release the retainer from the power piston and pop goes the piston.

But it wasn't the usual pop. It just kind of fell over the air horn and down into the choke butterfly instead of a full launch.

So I pull out the spring and do an instant OH! It's not the stock spring. After rebuilding 1400 carburetors I know what the stock spring looks like...and this aint it. So I walk over to the workbench (I did this teardown outside because it was a nice, sunny day) and grab a loose spring for comparison. The stock spring is 10mm longer. And that 10mm provides the extra oomph to get the piston to open the power valve.

Unfortunately I don't know Mike's user name on the forum to tag him with the pic.

 

[MudDauber]

Hey Mark,

As always, thank you Sir for solving this mystery! I cannot wait to get the carb back on the pig and perform some trail rides before summer gets in full swing. Thank you!

All the best,

-Mike