I would suggest a better quality "80cc" engine, especially if this is going to be your first build.
The Zeda Firestorm 80 is a much much better starting point and makes good power out of the box. There are countless people experienced with that version of the engine, so there is a lot of information and support out there.
Your source for 2-Stroke and 4-Stroke Bicycle Engine Kits, Performance Parts, and Accessories!
www.bicycle-engines.com
If you do desire a larger engine, like a "100" then I would personally go with the Zeda Max 100. It's a 2 piece design based around the same G4/G5 architecture of the "80" engines, but has the larger bore like a YD100.
Your source for 2-Stroke and 4-Stroke Bicycle Engine Kits, Performance Parts, and Accessories!
www.bicycle-engines.com
Just ignore all of the sales pitches and jargon words being tossed around on all of these websites that are trying to sell to your emotions. There is a ton of that floating around out there in the MB world. Bicycle-Engines also offers a small warranty with most of their enigne kits too, and they do honor the warranty. I speak from personal experience, having had multiple quality issues fixed by them with no fuss. They sent me a new part quickly.