In October of 2016 there was a post about the failure of the primer fuel line leading from the gascolator. Here is the link. In that post I suggested it was probably a good idea to cap or completely remove the priming systems from the Carbon Cub, pending a redesign. Unfortunately, I never got around to it.

Yesterday while performing a routine inspection I discovered the fuel line leading from the primer pump to the cylinder had fractured. See image below.



The primer in the Carbon Cub consists of 1/8" copper tubing in two segments: one from the gascolator to the primer pump on the instrument panel and the second from the pump on the instrument panel to aft left cylinder. My failure was in the line from the pump to the cylinder so there was no fuel leak from the brake. The cylinder had a small leak through the primer fitting but it did not change engine performance that I could notice.

The post from October, 2016 involved a failure of the line above the gascolator on the way to the pump. This kind of failure is very serious business as it introduces raw fuel on the firewall near the exhaust.

Today I completely removed the priming system from my 2014 Carbon Cub. The process is very simple all you need are two 1/8" NPT Allen Head Pipe Plugs. Here is a link to aluminum plugs on Amazon. Here are the steel plugs.

I put a steel plug in the cylinder and an aluminum plug in the gascolator then removed the tubing.

In my opinion these failures are safety hazard that clearly call for a mandatory service bulletin to remove this system until a redesign can be undertaken.

I have had a Carbon Cub since 2010 and never required the primer to start the engine. I have heard from folks operating the Carbon Cub in Canada who claim they normally don't need to prime the engine. When you consider the safety hazard associated with running a fuel line to the cockpit and back to the engine for a system that is rarely if ever needed, it would seem prudent to just remove the priming system.