I have not had that bad of "luck" with those Walbro carbs. No matter the brand, my biggest carb issues are with non adjustable ones.
The one carb that I scrapped, did run when I got it, it was on the M8 I have/ which was bought from a swap meet. I just set about "going thru the maintenance" on that engine, the carb looked dirty on the outside so I figured the inside might be too. This engine WAS to go onto my Troy Bilt Horse, which was stolen from me before I got around to the engine swap. so I just left that engine under the bench and forgot about it for a while.
So, I went to clean out the carb and I had it do something that I never had a carb do to me
(not to this extent anyway) -- I pulled it out of the dip and it started to oxidize on me within a day. Threw it back in, came out ok, and it did the same thing only worse. Repeat, came out clean, oxidized worse again after sitting on the bench. Each time I dunked it, it came out a little less clean, as in less of the oxidation was removed in the soak each time. I soaked it and rinsed it 4 or 5 times before giving up on it, that carb I cleaned in a bucket of berryman's, each time.
It has been sitting a few months since then, and it oxidized so bad that the shafts seized up solid... I went to put it together and gave up on it, This carb has been sitting in my dry garage the whole time. Like I said above in this thread, it looks like it was dredged from the bottom of the river. so it is absolutely no good now.
I was gonna steal the throttle shaft from it that's why I'd kept it/ but it was seized so tight that it became a lost cause. I just ordered new throttle shafts for both of the 8HP carbs that I have, a few days ago from Brian Miller. Incidentally both of these carbs came out looking new. One of them had a little oxidation on the last 1/2" of the "stem", the part the main nozzle and the bowl nut screws into, that carb started out as one of the nastiest, varnished up carbs, that I have ever tried to revive. I have a brand new can of dip, I got the GUNK stuff this time, which did not do much by itself, (it is badly weakened from its heyday, thanks EPA) I did the carb a que in boiling lemon juice to start, then finished in the dip.
Probably should have done it in the opposite order but did not have the can of dip yet when I boiled it. I do not think either process by itself would have been enough for that carb.
The "Mac's" brand carried by NAPA used to be the best carb dip available, have not used that in years, I went by NAPA to see if they still had that stuff, they still sell it but were out of stock, so my buddy there ordered some for stock and is holding one for me. I'm headed out to pick that up today. have no carbs that need dipped at the moment, but at least I'll have it for the next time.
I think it's time to see about getting one of those ultrasonic thing a ma bob's.
One of the #30's I just cleaned is slightly oxidized since being cleaned but nowhere near as bad as that original M8 one did, and this #30 does not seem to be getting any worse. That is the one going on this newly rebuilt M12 that I have, the original carb from that engine will become the spare for my other M12, the one on my Woods ZTR.