There was a strange bit of plumbing that made no sense. Barb connectors had been added to the intake rocker cover and primary cover. A hose ran directly between these connectors. According the britbike forum, this served no useful purpose. Sometimes venting is added to the rocker box and/or crankcase to help prevent leaks. It makes no sense to pressurize the primary by venting the rocker box into it. I removed the single hose and replaced it with two short sections of hose to vent both parts of the engine.