Topic: Air tubes for K7

[jawntybull]

I have just bought a k7 CB750 for a restoration project and am building an inventory of missing parts. The bike came with a loose airbox (not installed). The airbox has four hard plastic tubes that rattle around and are clearly meant to be attached to the carbies. the problem is that the diameter of the tubes is the same as the carbie inlets. In other words it appears that each tube should have a rubber attachment that is then clamped on to the carbie to join the lot together. I assume also that if a rubber connector is meant to be on the tubes, it would seal off against the airbox too and therefore stop the rattling around problem.

Is this correct? If so I am missing the rubber connectors and the clamps... in that case can anyone suggest a source for these? In the Honda parts book the rubber connectors appear to only come as part of the hard plastic tube assembly.

[doobiebro]

The loose airbox could be for an earlier model 750.  Prior to the '77 model, the carb inlets were 39mm.  For the '77 and '78 models, the inlet went up to 42mm.  If you have a '76 or earlier airbox, the connecting tubes would be too small for the '77 carburetors.  Normally, the connecting tubes clamp directly to the carburetors.  You can still get new connecting tubes from Honda.

[Duke McDukiedook]

A picture of the offending part would help.

[jawntybull]

Thanks guys, I have ordered new tubes so will see how they go. The old ones were so hard that they were more like plastic than rubber. I measured the OD of the carbies at it's 46mm - I assume that 42mm is the ID?

[doobiebro]

I am not sure whether the 42mm is I.D. or O.D. to be honest.  The simply remembered the measurement from when I bought pod filters and the shop first sold me a 39mm set.  Those did not fit, but when I exchanged them for 42mm I had no problem.

One thing you may do to be certain of the fit is to check that your carbs haven't been replaced with some from another model.  There should be a marking on the bottom of the outside of the #4 or #1 carb body that describes the carb.  I am away from my motorcycle at the moment, but I believe it should read "PD41A".  The manufacturer is Keihin.