This 13mm screw cap has 3mm extra length.

If the first threads in the housing are worn, preventing the original cap from being tightened, this longer cap offers a solution.

However, this doesn’t apply to all carburetors with a 13 mm screw cap: in some models, the overflow channel is positioned lower, so the longer cap blocks it.

In that case, the cap can be installed with approximately 1 mm of extra thread.