There are those words again: quality control

This is the biggest problem the Chinese face right now, ensuring that they ship products of a consistent quality.

My SK50 (from the same factory as the JBA) came with a glow-plug hole that was so far out of spec I had to re-tap the threads myself. Obviously they weren't running any kind of regular check on the tooling or engines because the plug threads were so undersized that the tap they used must have been worn out ages ago.

It strikes me that although the factory which makes Magnum, ASP, GMS and SuperTigre engines seem to have their QC sorted, the JBA/TS/SK factory has more than a little way to go in this regard.

If you're lucky you'll get a nice engine -- if you're not, well you might as well flush your dollars down the drain.