Hi!
All MVVS twin engines I have seen and run myself have the same design flaws. They are impossible to set rich despite open the needle all there is...

However...they are very easy to start, and throttle fairly well as long as you use glow power.
As soon as you remove glow power and throttle down and run the engine at low rpm...and then apply full throttle...one of the cylinders will cut out! I have tried many many different glow plugs and also used the 7mm and 8mm glow carb...all in vain!

Another design flaw is that if you want to use silencers instead of mini pipes...one of the silencers will be in the way when you try to adjust the high speed needle.