Pilot circuit question - '79 GS1000

[Guest]

Looking at the original carbs on my bike, I have something brass plugging the hole into the carb flow path. I had thought that someone had broken off needle tips in the holes, but now I wonder if they were plugged on the original assembly. I think I have read somewhere on here that some of the '79s were made this way. Am I hallucinating or is that real. Please help me if you know for sure. Thanks, Ray

[Nessism]

I’m not an expert on the history of the VM carbs but it seems to me that the pilot circuit needs that small hole in the carb body in order to work. I could imagine Mikuni removing the adjustable pilot fuel screw (like on the VM 29 Smoothbores), but in that case there wouldn’t be a pilot fuel screw at all, yet the orifice for the passage would still have to be open.

Do your carbs have the pilot fuel screw, and if so, do they have the sharp point on them? If you have the screws yet the tips are not pointy, they are most likely broken off in the carb body like you suspected.

[Sandy]

In some spots on the carbs where they had to drill the passages they sealed the drill holes with what looks like a small brass bearing or plug. For instance (IIRC) there is a vacuum passage on your #3 carb and vents on your #2 and #4 that share the same hose barb. The passages for both circuits are drilled into all 3 carbs and they use the plugs to deactivate the circuits they don't want. I hope that's what you're seeing and not a broken needle.

[rustybronco]

In some spots on the carbs where they had to drill the passages they sealed the drill holes with what looks like a small brass bearing or plug. For instance (IIRC) there is a vacuum passage on your #3 carb...

You RC, the #3 carb is the only carb with the BB closing off the bowl vent passage.

[Guest]

OK, I'm sure what I originally thought to be the case is correct and must have misunderstood the sealed passage for the pilot circuit opening. I could not understand how they would have been able to function without the pilot circuit either. I will now try to remove those broken tips and use the original carbs, as the junkers I picked up for free are not wanting to operate well. Thanks Folks, Ray

[Guest]

Thanks again for the responses. With a little effort I was able to remove the offending tips from all the carb bodies. I can't imagine why someone would continue to break off the tips after encountering a problem in the first place. Anyway all's right with the gs world again. Thanks, Ray