72 DS7 carb missing part?

[ampzip]

Hello, new member. I recently purchased a 72 DS7, and I love it. It hadn't been used for around 20 years. I bought it from a guy who had a local shop tune it up to get running.

I've put around 50 kms on it so far, but the other day went for a ride and it had almost no power, wouldn't stay running. I pulled the plugs and noticed one was very dark, and the other was black and wet, clearly running rich. It was hot that day (30 Celsius, 85) which would contribute? I also put high octane gas in the tank, which would make it burn slower, so could these two in combination cause the richness?

I don't really know the state of all of the ignition related components, so will need to test those as well.

In any case, I pulled the carbs and noticed what looks like a tube missing in the right side carb. Anyone know what the function of that tube is?

Edit: Pictures

[SoCal250]

The tube in the left carb body is for the enrichener (choke) circuit. The right carb does not have one because it is fed from the left carb by the short hose connecting the two carbs when the choke lever is pushed down.

[ampzip]

Great to know the carb isn't broken. Thanks

[m in sc]

take the jet tubes out and cleaned the carbs . prob what it's so rich.  tbh you can run these on 87 to 100 octane they are fine when stock. 

[DesmoDrew]

   Also, when putting the carbs back together after cleaning, note that the bowls are 99% identical, and can be interchanged by accident.  The bowl that goes with the left carb that has the brass tube will have a little hole at the bottom of the chamber that the tube inserts into.  That little hole feeds the fuel to the choke (enriching) circuit.
   Easy to swap bowls by accident and then the bike is hard to start after cleaning/rebuilding the carbs, because the choke is not getting fuel.