Modern Vespa

PX200, electric start is giving a clunk, but not turning.

Just had an engine rebuild, to replace seals, and kitted with Pinasco 225 at the same time.

Had an issue with bottom fin and flywheel, but cut fin back until flywheel was moving freely.

Electric start worked fine before rebuild, but now just gives a clunk and doesn't turn over.

I can kick start and when started it seems to run fine.

Battery aside (it's fully charged and giving me 11Ah on a 9Ah battery), where do I start with fault finding?

Some issues I have read ..
1) studs on kit protruding and jamming
2) compression too much with new kit
3) brushes on starter
4) starter relay

How do I check the possible faults?
Any other possible causes?

Thanks

Hello.
Cut the problem down the middle and see what side it is

1. Turn off petrol tap.

2. Remove spark plug

3.Put spark plug back in cap and place against the engine body somewhere so it can spark freely. This will protect the CDI from blowing itself up

4. Now turn the engine over with the electric starter.

5. If it doesn't turn over, check all electrical connections are clean and well connected. especially the heavy cables which carry all the current. A 1volt drop at the starter motor can be enough to stop it working properly.

6. If that doesn't work, have a pint of "Bucky"and wait for the next idea.

I'd measure how many volts the battery has to start out with. Then I would check the grounds (earths).

Problem solved ..

One of the things I replaced during rebuild was the flywheel cover. Badly fitting cover was preventing the starter from extending far enough to connect with flywheel teeth.
A bit of bending and bashing and I created enough space to allow connection.