Back drag carb - Vent jets

[Kargh]

Carb Part #: 1368-5676

One of those fancy backdrag carbs. Mine happens to be WMK-22 but it seems the main part number is used in several of the WMK-xx carbs.

Anyways, I've read, or so I seem to think I've read, that the vent jets should be removed and the economizer hose blocked with a BB. When it comes to the vent jets, do you just remove them and leave the port empty or should it be capped?

 

[jimmbo]

The back drag carb was introduced in about 1975, it leaned out the mixture under certain operating parameters by lowering the atmospheric pressure inside the fuel bowl. Lower pressure, less fuel pushed into the venture. Worked very well. But gasoline today is a far cry from what it was in the 70s. Todays gas has oxidizers blended in and ends up being too lean with these carbs. I guess a larger vent jet would reduce the leaning but probably would reduce the economy difference to very little.
If you want to disable the back drag feature, just put a small ball bearing in the hose, and reattach the hose tot eh nipple. The vent jet can remain as still will provide enough atmospheric pressure to the fuel bowl

 

[Kargh]

Thanks for the reply. Yeah, that is pretty much what I've read in regards to disabling the back drag. Perhaps you can answer another question:

I removed the idle adjustment screw and spring. When I did that, a small, opaque bb rolled out as well. I don't see this on any part diagram for any of the carbs I've looked at (I've not been able to find a diagram for the WMK-22). Any idea what this is? I assume it just pushes down into the idle tube to help block it?

 

[jimmbo]

a ball bearing was behind the idle mixture screw?

 

[Kargh]

Yeah. I can take a pic of it if you'd like to see it. It was in the idle tube on all 3 carbs, and on the spares I have.