As you have found, the carburettor settings are pretty critical and need only the slightest adjustments.
However you seem to be getting there and at least you can complete your work.
Several factors come into play as the machine gets a few hours behind it.
First, the carburettor wears to some degree.....jets don’t wear to any extent but the needle on the throttle slide does.
Secondly, two stroke engines rely on good crankcase oil seals.....these live on the ends of the crankshaft where it exits the engine castings. Any wear on these allows air to be ingested into the engine and this plays hell with the carburation. If you can grab the flywheel and feel any up and down play whatsoever, expect the seals to have seen better days.....Its only very high hours machines or those fed on poor oil that suffer this way.
John
However you seem to be getting there and at least you can complete your work.
Several factors come into play as the machine gets a few hours behind it.
First, the carburettor wears to some degree.....jets don’t wear to any extent but the needle on the throttle slide does.
Secondly, two stroke engines rely on good crankcase oil seals.....these live on the ends of the crankshaft where it exits the engine castings. Any wear on these allows air to be ingested into the engine and this plays hell with the carburation. If you can grab the flywheel and feel any up and down play whatsoever, expect the seals to have seen better days.....Its only very high hours machines or those fed on poor oil that suffer this way.
John