I bought mine with the issue also and it was very confusing at first where i spent 3 attempts on it. Although it was a good bargaining point

.
Id try a repair kit which is 25 quid.
or start by checking rods with a ball joining end and ensure the clips are all tight that lock them on the balls
second thing is at the very back of the engine is a shaft with a round ball attached. this has two top hats either end, ensure these are on the outside of the bracket are as they can be fitted wrong.
Third slacked the clamp on the shaft that goes to the gear lever. the shaft can be moved back and forward and side to side. its real trial and.error but see if you can then get first. But make sure its not 3rd trying to trick you by starting up and pulling away. once you have a rough feel for them all finely tune it with the adjuster on the lever
Adam