RE: pros and cons of 2 and 4 stroke engines ?
There actually is a potential problem in the use of a remote needle valve with two stroke engines.
The main pressure drop in the fuel delivery system occurs across the needle valve. With a needle valve in the carb this does not present a problem, & in fact, assists in fuel vaporization. However, with a remote needle valve the pressure drop is still at the needle, but the fuel now discharges into an additional length of fuel line, which also causes a frictional pressure drop. Additionally, the suction (negative) pressure from the carb throat further lowers the pressure in the fuel delivery tube to the carb. If the combined pressure reductions exceed the vapour pressure of the methanol in the fuel, it will vapourize in the delivery line & produce bubbles (flashing). Flashing is even more likely if the delivery tube lies near the engine case & is heated by the engine. The whole business is even more compromized by operation at high ambient temps (a nice warm sunny day).
Flashing does not always occur with this remote configuration, but it happens often enough to be a pain. Many fruitless hrs have been spent by modellers searching for pinholes in tubing & various other causes for the bubbles that plague their fuel delivery & tuning when, in fact, it is flashing. I avoid remote needle valves on 2-strokes like the plague.