die Bohrung indessen legte tuechtig zu

07:24 Apr 6, 2017 

The additional context does not mention any reboring, but shorter stroke of the piston. reboring means grinding off any scratches and fitting an oversized piston. It's still unclear, whether the bore diameter has been changed. On the other side, I wonder, how the engine power was boosted. A shorter stroke may enlarge the displacement, but reduce the compression. This can be (over-)compensated by boring the cylinder and/or modifying the cam, i.e. the ignition point.

03:09 Apr 6, 2017 

What it deals with in that paragraph is how the bike was adapted after the head had been refurbished. The sentence before it reads something like: For the cam, the master builder orientated himself on the shorter strokes of the later Manx engines. And then follows the sentence in question.

21:59 Apr 5, 2017 

... the conversion of a Norton Manx engine."
This would seem to imply a 'rebore' of the engine.
"I sort of know what it means..."
Does the context suggest that a 'rebore' took place? Please confirm or otherwise.
Thanks

13:55 Apr 5, 2017 

After the rebore, the engine produced a lot more power.

Not sure how the 'indessen' fits in without seeing the full context.