Ref: LD125 1958 model – late serial numbers.
If I were to try to date an engine, I would use the other BLA website here:
http://www.lambrettaframecheck.co.uk/pages/ItalianFrameInfo.html
It is the only one that I know of that lists serial number for Lambretta engines and was also put together by the BLA. NB: This BLA website also shows the higher (1957+) frame numbers up to 566718 (LD125 57 – 1958 model).
I have many Lambretta books. However, I do not have any with engine number date references.
This BLA website shows that for a 1958 LD125 and with your serial number, the (engine) range should be between – 330710 to 344718, which would imply your engine is original, given the number you provide me.
Note: I normally use this BLA website as a guidance for engine dating. For this example, if I found a 1958 LD125 Lambretta with your frame number and it had an engine outside the range above (But within one year), I would assume that the engine was original. I mention this as I have a number of Lambrettas and some fall outside the advertised range (by one year), but I believe they are the original engines for a number of reasons.
NB: Some reasons for an engine replacement may include when replacing the engine mounts, due to force used, the lugs get broken (Where the rubber mounts are located). Another may be that a person is not able to get the mag flange off if they need to carry out a seal or crank replacement and they break the case. These are problems I have had in the past.
For further information on your Lambretta LD and dating history and information, please see the attached images (Check email) that I have taken from the latest book produced by Vittorio Tessera (Founder of the Italian Lambretta Club in 1988 and founder of the Scooter & Lambretta Museum in Italy) and released this year. Note: one of the images reference the earlier models and are attached for your interest. These two pages apply to the Lambretta LD125 only.
All the best and have a good weekend.
John