[Rickwales]

Chances of having the right jets in your carb straight off the shelf is pretty unlikely. The needle height only really affects the way the engine accelerate through the rev range. The engine boging or running rich is not connected to to what gear you are in. If you're old carburettor was running fine and then started to play up and you found no amount of judgement could get it right then the first thing to do do is check the valve clearances and then strip and clean the carburettor completely including the little holes in the emulsion tube when you take the jet out. Carburettors don't just stop working they either get clogged up or or the valve clearance alters which then gives the impression there is a carburettor issue. If you found the engine was difficult to start what and / or you were getting fuel blowing back through the carburettor into the air filter then the issue is with the valve clearance.