I was having some carb issues on my new-to-me 58 Duo Glide. I pulled the carb to see what was going on. I found some things that were missing or needed cleaning, but I found a hole (that had nothing in it initially) that I didn't see in the manual that is puzzling me.

Please see the first picture -- the nicely machined hole (no threads) is above the float bowl; if the carb was mounted, it would be toward the rear cylinder. I sprayed some carb cleaner in it to see if it went anywhere and got spray into the venturi and down into where the bowl would have been.

The second picture shows a rebuilt carb of the same model. It appears to me that there is a plug in that hole. Can anyone confirm or deny the plug? If it should be plugged, any idea what material or part number?

Thank you,

 

I've got an M 51 on my 38. It has the exact same hole. What we have here is your float bowl vent. One question, when you sprayed into the hole, did you have any gas in the bowl? That hole goe's in about 3/8", then angles down at a 30-35 degree angle. Nothing to concern yourself about. And I wouldnt plug it.

 

mine is open on my 64. and its a bowl vent

 

Gents,

Thanks for the insight. Having a vent that goes into the perimeter groove of the venturi seemed a bit counter-intuitive to me (kinda like a vacuum leak), so I appreciate your help.

Flat Head -- I already had the bowl off and everything else removed when I sprayed carb spray in it. FWIW, I was able to slide out the venturi tube and was then able to see how that vent was ported.

Thanks again,