Thanks Rivets for your reply - I saw those two specs in the manual - and it's not obvious which one applies !
I thought it was probably the small gap but I can try the other.
Greetings from Somerset, UK. I'm coming to this forum as there seem to be a lot of knowledgable people looking.
I have a Flymo L400 hover-mower which I've owned since new (about 1997) and the engine is a Tecumseh TC300 ( TC300 3156 (F) ) and the carburettor is a Tillotson HU, and the ignition...