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Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 11740
Experience:  25+ yrs. experience
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Starter works great, battery good, but my C900 is starving

Customer Question

Starter works great, battery good, but my C900 is starving for gas ... I have to take off the gas line from the fuel shutoff valve to the diaphragm and let the gas drain for a few seconds. before I can start it.
JA: When did you last fill the tank? And do you smell gasoline around the engine?
Customer: New gas ... no gas smell
JA: What is the model/year of your motorcycle?
Customer: 1981 CB900 with the high low gearing
JA: Are you fixing your bike yourself? What have you tried so far?
Customer: I bought it a few months ago and immediately put it in a local shop that specializes in older bikes, they rebuilt the carbs ... I'm trying to fix it now.
JA: Anything else you want the mechanic to know before I connect you?
Customer: I am idiot ...good at reading manauls and watching videos
Submitted: 5 months ago.
Category: Motorcycle
Expert:  Louie replied 5 months ago.

Hi, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.

Initially, proposed preliminary checks (if have not been done) :

  • • drain-clean tank and replace with fresh fuel (even if just to eliminate as a suspect);
  • • verify air box, filter, duct and coupling correctly fitted with no air leak;
  • • check fittings as some versions would have a vacuum feed/lock that allows fuel flow if and only if the engine is running;
  • • check/clean filler cap vent hole (least likely);
  • • check/clean strainer/filter of the petcock/shutoff valve (likely);
  • • ensure correct float adjustment to allow sufficient fuel to the bowls (most likely).

Please click HERE for the chapter of fuel from the Service Manual.

It is in a Portable Document Format (PDF) file and can be viewed in most web browser. Click on the link to open the file or right click then select “Save As…” to download the file. It would require Adobe Acrobat Reader or equivalent for this purpose.