Check your diaphragm
 

No lady's not THAT diaphragm .:p..the carb vacuum piston diaphragm.
A fellow SH owner was in need of a new one due to his having a hole.... I had a bunch of spares so sent him one........he found a crack in the rubber...so I said Id send him another....... I went though 5 sets of spare carbs to find ONE diaphragm without cracks or holes rubbed in them. so from 10 vacuum pistons I had, 9 were bad with holes and cracks in the rubber diaphragm.
Of course I had to check the set on my bike now......and sure enough even though I felt no runability issues, the front one had a small crack in the rubber..likely not leaking much if at all, but it would have soon.

So two new ones ordered up at $62 a piece .. Surprising, that's cheaper then the smaller one I replace all the time on our training bikes..that little mikuni 28mm carb piston is $78.. But a whole new carb is only $198....wish the carbs on our bike were that cheap to replace. ($400 a piece)
So get busy, and check those rubbers for holes boys ...lol

Did you buy OEM ones? I just bought a set for $100 a piece.

MSRP full retail is $104.56 each.
Common street price on line is $80.56 each.Yes I just bought a set, at $137.74

Sorry you paid so much, have a look at online retailers next time Partzilla.com $80.63 each https://www.partzilla.com/product/ho...466e917f56e1ff

or $83.60 each Ronayers.com https://www.ronayers.com/oemparts/partsearch/honda

Those are that expensive? Why does that seem like a lot of green for 2 flimsy rubber diaphragms?

Well it is the resin / plastic valve as well.. But ya, I know what you mean.

I have 62 Kawasaki BN125 trainer bikes I maintain...the Mikuni BS28 carb has the main vacuum valve (like ours) and a small coast enricher valve about the size of a quarter. The larger vacuum valve is $75 my cost the smaller one is $95 ..$170 for just two wear items,,,, They sell me the entire carb for $190...
Bit o rubber and plastic (or rubber and brass) is damn pricey

I went through my local dealer. I guess that's why. Oh well, They were able to get them in less than a day.