I would replace that spring with a factory part. Shortening the spring will change the spring rate or tension and will not provide proper engine speed control. It will most likely cause the engine to run at a higher speed than spec.

When you cleaned the carb did you do so in a chemical bath or ultrasonic cleaner? If not one of the very small passages may be blocked and causing fuel starvation which leads to surging.

I think the low speed jet is dirty.Honda has a limiter cap on the low speed jet which can be removed if you are very careful.
Is your unit a straight HRX 217 or a HRX 217 HXA?
Reason I ask the HXA will idle different with the blade off tha on.
Try this
Get a long Phillips screwdriver and turn the idle stop screw in one or two turns and see if that mekes a difference.
Then let me know what happens.

I agree about the price being cheap, but that is a easy carb to rebuild. Nothing usually goes bad.
Also the new carb comes with a cheaper float bowl and you have to remove the one from the old carb. Heck if you go that far make a attempt to rebuild and learn.
You will need some long 6mm studs to properly align the carb.
This is very important.

I replaced mine in ~15 minutes and it now runs like a champ, no studs or bowl changeover. If time has no value then knock yourself out, but these carbs are literally disposable. Plano had mine on my doorstep in a few days.

How could they possibly sell a complete Honda carb for $15 ???

"How could they possibly sell a complete Honda carb for $15 ???"

I believe they use currency?

http://www.planopower.com/store/honda/hrx217k1tda.php

The use of 6mm studs really helps align the carburetor. If anyone wants to change the carburetor the studs will save you time and make the alignment easier. And you will not have any chance of air leaks.
The new carburetors do not have the drain option. So, it is best to have the drain attachment. This is most likely what caused the original problem. Not draining the gas.
The old carburetor had the drain option. The new does not.
The blade brake units have a heavier flywheel and they will idle better than the ones with the flywheel brake off system.

I like the idea of the studs. It can be a hassle trying to get a bolt through all that mess.

My comment about the carb's price was rhetorical, as you know. They must now be using unemployed Chinese prisoners to make something with all that machining so cheap.

Probably the actual cost is about $7 bucks. Makes you think how much profit there are on BS, KAW, Kolher Carb. ??????? maybe mark up and retail is usually 300% or more????

Sometimes the air/fuel idle mixture screw could be adjusted too lean causing the surging if it has one. I would try to adjust it counterclockwise 1/16 to 1/8 turn see if that helps the surging?????

The ethanol in the gas attracted all that water in the carb while the mower was sitting. I had a guy get a HRX from his father unlawful that sat 1.5y and he couldn't get it running. When I got it the bowl was filled with rust colored water and the bowl was certainly rusted. I got a rebuild kit (didn't know the carbs were $20 at that time or would have went that route) cleaned the bejesus out of the bowl and all passages/parts carb related, put it back together and it started first pull!

I actually have a Plano carb sitting on my toolbox for my HRX, just waiting for the need to slap it on!