Motobecane carb

My 78 motobecane only has a top speed of about 24 mph. If I give it a little choke it will get up to around 30. What can I do to get this speed with out using the choke. Does the carb need cleaning or a larger jet. Also is there any adjustment on this carb besides the idle stop?.

Bob

Re: Motobecane carb

The choke cuts off air through the carb, so the fact that you run faster with it closed partway means you're running too lean (too much air per amount of fuel). What you need to do is make sure that all the normal stock restrictions on airflow are in place (airbox, air filter) and that you do not have an air leak between the airbox and carb, or carb and intake. Spray carb cleaner on suspect areas with the engine running to find leaks.

Re: Motobecane carb

Bob Phillips /

Thanks Matt: The problem is I don't have an air box for it. I got the bike for free and it was missing the air box. It does have the small air filter with the screen on it but not the cover box. Can you tell me if the air box has foam or some other material in it that would restrict the air flow. I looked on the Moped junk yard for the air box but it says they are no longer available. I may have to try to make one but I still need to know about filter materal.

Thanks.

Bob

Re: Motobecane carb

There is no foam or any other matierial that further filters or restricts the air flow. Just small holes in a large box.

Re: Motobecane carb

Bob Phillips /

Thanks Bret, I guess I will have to make up some thing to help keep the air flow more consistant. I notice the problem is worse going into a head wind. I think air is being forced into the carb.

Bob

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