also check for an air leak when you close the throttle,i have had several people bring me engines they have rebuilt but didn't get a good seal when they put it back together aluminum does and will warp when heat is applied from prior running !!!!! and you take the engine apart it will tweak that is why when you rebuild automotive,motorcycle, engines with aluminum heads, blocks ect. they machine them resurface them!!! i have had 2 dle 55 that i had to resurface the crankcase to the cylinder, also if you split the crank case and there is no gasket you need to reseal the case with anerobic gasket maker from permatex!!!! do not use silicone!!! a closed throttle should go to idle with a sealed engine,also you may re kit the carb the diaphrams are only good for so long !!! this to will also give you eratic running...,engine timing only affects rpm and power!!!! if you still have problems i would gladly take a look at it!!! for free!!!! i do have references if needed!!!! also the low speed needle only affects the idle and transition for full, the high side is just that only high rpm. i also accept that everyone has an opinion and weather right or wrong i hope my info. will help you!!!!!! mike