Topic: Carb Vents? CB750K2

[bird]

Can someone please explain what carb vents/carb vent holes are, and where they're located.

I've searched my manuals and the forum for a clear answer, but no luck. If you can post a photo or illustration even better. Many thanks. bird

[Markcb750]

I think a carburetor pdf is available on the website.


Have you read it?


http://www.sohc4.net/?q=node/65

[CB750F2]

G'Day from Nth Qld. The purpose of the vents is to keep the space above the fuel level at atmospheric pressure. The venting is provided by a standpipe in each fuel bowl. This standpipe is vertical and is long enough so that its opening is above the fuel level. The bottom is connected to external hoses at the bottom of the fuel bowl. These hoses also double as drain lines. The hoses block up occasionally so they need to be checked.
Some carburetor models also have small drillings in the space above the fuel bowl. These holes are bridged together with short hoses and then to atmosphere. These holes provide additional venting and equalisation of pressure above the fuel level. If the vents become blocked flooding will occur because the space above the fuel level becomes pressurised forcing the floats down and allowing fuel into the bowl. Hope this helps, Pat

[Johnie]

The 2 black hoses in the middle would be the vent tubes. They usually drape over the top of the OEM air box. Keep in mind the 2 horizontal black tubes between the carbs are also vents. Click the pic to enlarge it.

[bird]

Thanks guys, one and all. I've downloaded the carby tech stuff, will look for the holes and issues you mentioned Pat, and cheers to the last guy for the photo. I'm a simple mechanic. Big pictures I understand! ^^

[kghost]

Nother Brissy member.....man...thier multiplying...

[Spanner 1]

Really, really good explaination Pat, on the bowl venting....kudos.

[Terry in Australia]

Thanks pat, and I'll have to check the CV's on my K2/F2 special, there might be a blocked breather issue with one or two of the carbs, considering the fuel dribbling out of the airbox.................