I have a similar problem:
I have a Haibike Trekking 6 i630 (2022 model) with Yamaha PW-ST motor and 38T chain-ring. The chain-ring is dished and all in one piece; it slides straight onto the motor shaft - no separate spider. The chain-line appears to be 52mm, and the OLD is 148mm.
I would like to raise the gearing, as I spend a lot of time in the top two or three gears. With a 10 speed 11-46T cassette, hill-climbing is fine and I don't use bottom gear or high power very often.
As far as I can tell, I'll need a spider and separate chain-ring, perhaps 40T or 42T. I don't know whether going larger would compromise hill-climbing, although the motor does appear pretty strong. I've seen spiders for other versions of the PW motor but not specifically PW-ST, and they are out of stock anyway.
Is any PW-** spider likely to fit and have the correct chain-line?
What size chain-ring should I fit?
Where can I buy the parts?
Any thoughts or ideas, anyone? Am I on the right track, or heading for a pitfall?!
Thanks in advance.