Plan on speeding at least $300 to $400 to make it reliable.
I have several new edition Whizzers [at least 6] and several have over 6000 miles each on them.
Totally plan on replacing the entire top end because the metal is soft and the threads WILL pull out of the cylinder. Sadly even heli-coils won't hold in the aluminum. The head will run way too hot [90 degrees hotter than earlier models]. Some of the NE-r models have a single valve seat block and the valves will lose their seal when the block shifts or loosens, requiring the cylinder to be replaced [it should be replaced PERIOD].
I have modified hundreds of these motors and I agree they are worth the effort, but some versions have more problems than others.
I am currently working with the new heads to make them run at an acceptable tempature by cutting the fins deeper [using and end mill], and I do think it is possible to make them work correctly.
Very seldon [almost never] are a few minor adjustments going to make you happy, but the problems are fixable in the majority of cases.
The main advantage of the NE-r and Ambassador II are the disc brakes, but understand the wheels, forks, and brakes are very heavy compaired to earlier models, therefore they aren't as fast. The larger tires make it ride better, but extra caution is needed to ALWAYS make sure the air pressure is correct because the side walls are very, very, very soft and can be destroyed easily [I have replaced 2 tires on my Ambassador in under 1500 miles].
You now have the facts, so buy it, modify it, and enjoy. The Whizzer motorbike is different from all others and can be a lot of fun as long as you are willing to fix a few things early on in the process.
These comments are centered around the NE-r because you ask about that model, and earlier NE5 models don't have the same problems as the Ambassador and NE-r. The best model with the least amount of problems is the 2005 and 2006 NE5 models, and often installing a copper head gasket, a set of mushroom lifters, and installing a hardened bearing sleeve on the automatic clutch will cure 99% of the problems on the earlier versions.
Have fun,