Motorcycle Repair: cb160 carb, check ebay, carburetor body

Question
Hello.  What is the little flap on the choke slide for and is it necessary?  I'm missing one, just the flap part, and since parts diagrams don't identify it, I can't order a new one nor do I know what it's called.  Will the bike run with just one on one carb?  Thanks, Andrew

Answer
Andrew, unfortunately the flapper doors are not a replacement part. And more unfortunately, the the doors and the springs get sucked into the motor when it is running, causing severe damage in most cases.

The flappers were put in the choke plates to keep the engine from being over-choked when the choke lever is pulled all the way up, cutting off about 99% of the air to the engine, causing a rich mixture which can foul spark plugs as well as creating atmospheric pollution.

If the engine is in good shape and well-tuned, the chokes are generally not needed beyond the first few minutes of operation. Choke requirements vary with altitude, humidity and temperature. Once the choke lever is pushed down the choke plate recedes into the carburetor body channel and is out of the airflow path.

I would keep a close eye on the condition of the carburetor which still has the flapper door attached. Usually the tension spring end breaks first, then the flapper starts flapping back and forth rapidly, failing soon and then gets ingested into the intake tract and either wedges the intake valve open (bending the valve when the piston comes up) or the part gets "compressed" inside the combustion chamber, damaging the piston/rings, valve and combustion chamber surface.
Rarely, do they clear the engine without damage.

Check Ebay or other used bike sources for another carburetor body for the 160 (CB or CL) and rebuild it with your float valve, gaskets, o-rings, float and jets.

Bill Silver