Here is my MB5 right next to my friend’s Hobbit and another MB5. Right now I am running stock as it makes my daily ride much more reliable. I have deleted the oil pump with a block of plate and run premix. I have a trail tech temperature gauge and of few other misc things that I have done to it.
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Here is the other motor that I built for it:
New oem CDI
1980 CR80R 6 speed transmission
Polini 66cc kit
NSR50R 4 petal reeds
Barnett Kevlar Clutches and stiff springs
Racing Crank ,Bolt on intake for 20/24mm mikuni
plastic riser for 4 petals
22 mm mikuni carb
Delete oil gear and pump
Oil pump blockoff
New bearings and seals
Voltage Regulator
Lithium Ion Battery
Homoet 70cc pipe
Trailtech temp gauge
IRC tires
35 T rear sprocket
16 T front sprocket
MadMatMax 
Have you run the engine with the NS50 reed block ? Any significant improvement Noticed ?