Motorcycle Repair/cb160 carb

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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

Motorcycle Repair

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Bill Silver

Expertise

Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.

Experience

I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

Organizations
VJMC (Vintage Japanese Motorcycle Club) of North America

Publications
VJMC newsletter, as editor for two years and as contributing editor currently.

Education/Credentials
3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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