I have the same carb. On yd gy6. 155cc. 1500 feet roughly. Only half to use the choke when air temp. Gets in 50's or below. Even then only need to choke it once on full choke. Will die shortly. Then take choke off and fires up. If try to choke after its running. Will die. I haven't changed the jets. Using stock ones it came with. That being said I believe at lower throttle I think I'm slightly rich. But mid, and WOT. spark plug check looks good. It does bog slightly on take off. I've read that down jetting would be best for current setup. (Even with A12 cam..high flow intake and exhaust. Which I have.) The stock jets are good once you get into the 175 Bb. Kits. But I don't have 4V. So not sure how that applies in your case. But sounds like your setup with that carb. Reacts much like mine does. Plan on getting a 175 bb kit. Its not running so rich that I think its a big issue. Since do want to up grade. But if I wasn't going to upgrade, I'd go ahead and down.
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