I don't believe they are.
I have 4 different Ebay Kits from 4 different suppliers ( in OZ).
One was total CRAP!
If your in OZ do Not buy anything from OZ Bicycle En****s,
No concern for the fact that the courier took a month to get it to me,
Dents in fuel tank,
Crap unbalancd GT5 crank,
a teaspoon of metal filings in the motor,
Crappy exhaust also with a dent,
Mag lasted about an hour,
ect,...
Another Kit From Motow***s was alright except a weird barrel? and bearings missing out of clutch basket.
The last two kits also had faults. (one had no chance of the head gasket sealing with out lapping both barrel and head. the other had a flat spot on the clutch fly wheel teeth.)
Make sure you get one from someone who will honor warranty!
And check it properly before running it.
Everyone of my Ebay Kits had at least one issue!
Maybe I'm just unlucky?
Fussy?
There not all the same!
Try and find one with the straight fire head and the 40mm crank.