Scooter engine knocking noise

Hi,

My question is, can a scooter with an engine knocking noise pass the MOT?

My scooter developed a noise which sounds exactly like an exhaust downpipe hole which varies with engine speed.
After much investigation the noise seems to be originating from somewhere behind the variator.

Further investigation, exhaust is absolutely fine.
Transmission is fine as running with drive belt off noise is still present.
Engine oil is clean with no fragments.
Top end seems fine, noise not coming from there & compression is ok.
Next I will be removing and inspecting variator.
Then crankshaft & fittings.

Thx

Mark