Sometimes you get lucky, but the majority have had bad luck - including myself - I have boxes full of old and new carbs. Worst experience? A customer brought me an 04 Arctic Cat DVX400 with a brand new carb on it. His complaint; it would start and idle, but wouldn't take throttle. In my experience I determined it was not getting enough fuel as the throttle was opened. I removed the carb, opened it up to check the jet sizes - no size engraved on the jets - I looked at the outside of the carb - a HUANSONG HYQZC - on the other side WML0177 PD36J-C
When I started working on the vehicle, I did not know it was a Chinese 'will fit' unit, but when I went to remove it I thought it was curious that the throttle cable had a loop in it to enter the operator chamber on the air filter side. I was accustomed to seeing the cable enter at the 1:00 o'clock position, not the 8:00 o'clock position. My first obstacle was Mikuni jets did not have the same thread as the Chinese clone. So I started drilling out the main jet (I have an assortment of decimal drill bits in .001 increments). I improved the performance substantially, but determined that by the time I got it right it would cost more than a new carb. I asked the owner what happened to the original carb and he said he was trying to make the vehicle faster and was drilling out the jets. He explained he knew he bucked up when he broke a drill bit and found out the slide wouldn't move. In his effort to remove the slide, he tore the rubber diaphragm off the slide. He found one on Amazon for $45, bought it, put it on and found out it wouldn't run above idle, so he brought it to me.
Now the Mikuni carb for the Acrtic Cat DVX400, Kawasaki KFX400 (KSF400) and the Suzuki LT-Z400 is the exact same carb. In case you didn't know it, the quads were manufactured by Suzuki. Kawasaki owned Suzuki at the time sold Arctic Cat complete vehicles except for the plastic. They came complete with carb, air box, electrics and used the same Mikuni carb with the exact same calibration - plastic, wheels and tires were proprietary to the vendor. Parts from Kawasaki is cheaper than parts from Suzuki and Arctic Cat parts are exorbitantly high priced. The first time I ordered an Arctic Cat part it came in a package with the Suzuki part number pasted over with the Arctic Cat part number. The Suzuki part was about 1/5 lower priced than Arctic Cat.
I ended up ordering a Mikuni carb from Kaw $437, Suz $627 and AC $788 - installed it, adjusted it and it was done. I also had to have a new throttle cable because the owner messed it up trying to stretch and bend it to get it connected to the cheap carb.
I usually don't have many problems with Chinese carbs on Chinese machines, so TaoTao, Eton, Dinli, Yamaha Vino scooters, Suzuki LT50 & LT 80, Arctic Cat 90, Polaris 50's and 90's, Jonway, Coolster, Kawasaki KFX50 and numerous other brands and models, but 20 out of a hundred Chinese carbs are junk out of the box. Weigh the advantages and disadvantages and make your choice.
BTW, Chinese carbs are not good aluminum - they are mostly zinc - they are easily damaged by alcohol and most OEM manufacturers will not warranty them if they have had gas in them. They can also be damaged during cleaning and can be damaged while running if ethanol blended fuel is used.
Just my experience, but I keep the Chinese carbs on hand (2 of each). Damn scooters need them frequently and they are cheaper to replace than clean.