Possibly a vacuum in the fuel tank or a lack of fuel is restricting fuel IMO.

1. Open the fuel cap enough to know it is getting air.

2. What are the Approx fuel mixture screw turns from a light seating?

3. Give some history on the saw and when this started before the new carb.

4. Two cycle engines are so temperamental, they are retiring me to electric saws etc at home vs away.

I don't know how long you mess with it? IMO once you replace the fuel lines ( and carb.) takes awhile to get all the air out of the lines and carb. I would get it started rev it up and use some carb. cleaner down the carb. venture see if that allows it to stay running and hopefully work any air that may be trapped... After you do this several times and still no luck I would make sure the filter on the end of the hose in the tank is not restricting gas to be pulled up. revisit carb. installation making sure the gasket not partially blocking any small passages.

Point brought up by loger the carb. maybe too lean when the saw begins to warm up. Half choke should help in this case.. Don't know your expertise with two cycles when it comes to adjusting carb.

I have used and tuned lots of two cycles over the years. I get no lag when i accelerate from idle. Idle is slow enough to prevent chain rotation and still purr. problem is that even with new gas and vent lines I'm not getting consistent fuel flow apparently. I have ordered new check valves. That is the only part that I Have not checked. I even went so far as to remove the vent plug (porous metal filter on end of return air line) and that didn't change the problem. I suspect it is the check valve because when I open the fuel tank I find that the system doesn't cut off.

In case anyone is going to say something about the exhaust, I have run this saw pretty cleanly so there is absolutely no carbon buildup on the muffler (BTW, it would take one heck of a lot of rich fuel operation to foul a significant percentage of the muffler screen - speaking of this as a likely problem is a real red herring).

I asked my Son this question yesterday because my Sears 16" chainsaws only work about 3 or 4 years and then won't start (I have 2 that won't start). He said that the gasket between the carb and engine may have a crack in it allowing a vacuum leak so the fuel won't get sucked up to the carb. I will have to check that next in the mean time I ordered an electric Black and Decker one( I'm 75 and my arms hurt from trying to start these).

Also the fuel filter could be restricted , air leak at the carb or ignition module going south . Check valves ? no check valves within fuel system , perhaps a partially restricted inlet needle valve and a weak or stretched diaphram . Old thread just my 2 cents !

I'm still enjoying my 16" and 14" "Electric Saws " that are meeting my needs. That is working on the Half Mainly Splitting Wood due to my restrictions after a Neck Fussion. I am learning a New Lesson On Using Vibrating Tools.

I'll get back on Log Splitter Maintenance...

I use 3 different Electric Brands at home and have serviced more. I have not found one to complain about if Maintained and used "Reasonably". They have extended my 70+ Age use at home. My Electric Log Splitter is running a Tight Race with my Electric Saws. I feel the only difference is Electric Powered (with Hydraulics) vs Gas Powered. I have seen many Electric that w/n compair with "Good" Gas Splitters. Just as I have seen very Few Gas Slpitters that are not reasonable.

With today's compertition I am seeing some "Gas 27 Ton Splitters with All The Bells And Whistles (that I'll hope to Track Their Service).

Keep the wood chips flying Loger , look after that neck !