Topic: 77 78 Pd 750 carbs question.

[754]

The small vent hose near inlet fuel hose ..
 Goes to where ?
 What is its function?
 Part of the reason I ask is, there is the clip on both ends of the hose, like it secures it to something, and it was pointing up so it looks like stuff can get into the hose..

[Tdubsy]

Its just a breather of some sort,

should be routed upwards towards underside of the tank. doesn't connect to anything

[Pielz]

Can you post a photo? I should have these same carbs and I've never seen that on mine. Wanna know if I have something screwed up lmao

[madmtnmotors]

Some of the later PD carbs have this vent hose while others do not. I have examples of both but I can't get to the numbers on the carb bodies right now. This vent hose on my K8 CB750 is a two piece affair with each piece being 6 or 8 inches long joined with a straight inline coupling. Mine extends up to the top of the airbox where there is a cable clamp looking bracket that secures the hose with the open end facing to the rear. I'm guessing the two piece assembly would allow splitting the hose when removing the airbox without having to pull the hose loose from the bracket or the carb. This is the bowl vent for all four carbs that are joined by crossover tubes, similar to the crossover tubes for the accel pump, instead of having each bowl vent individually to the atmosphere. Evidently at some point in the development of the PD carbs Honda thought "hey, lets combine the bowl vents"...

If the carbs are off the bike you can trace the crossover openings on the sides of the carbs with a little compressed air or aerosol of choice. The vent crossover connections are inline with the vent hose connection IIRC much like the fuel crossovers are inline with the fuel hose connection.