I had the same problem, mine accelerated ok at low speeds with small gradual throttle movements, if I moved the throttle quickly it bogged down.
I fitted new needles, pilot jets and reset the carbs. I was running in and running rich but think it was due to the richness. I modified my slides from 3.5 to 4.5 and that helped as it also leaned out throughout the range. After I got the mixture leaned with the idle screw and lowered the needles I then fitted two new spark plugs as I have found that the Champion N5's don't like running rich with modern fuel . Once new plugs were fitted no further problems, I found that once a plug starts missing no amount of cleaning will cure the problem. One plug on the rear cylinder lasted 25 miles which I put down to a rich mixture killing it.
I'm running 289's so slightly different but I looked at everything and was pulling my hair out so I hope this helps.
I fitted new needles, pilot jets and reset the carbs. I was running in and running rich but think it was due to the richness. I modified my slides from 3.5 to 4.5 and that helped as it also leaned out throughout the range. After I got the mixture leaned with the idle screw and lowered the needles I then fitted two new spark plugs as I have found that the Champion N5's don't like running rich with modern fuel . Once new plugs were fitted no further problems, I found that once a plug starts missing no amount of cleaning will cure the problem. One plug on the rear cylinder lasted 25 miles which I put down to a rich mixture killing it.
I'm running 289's so slightly different but I looked at everything and was pulling my hair out so I hope this helps.