Motorcycle Repair: 1973 honda cb 350-carbs, honda cb 350, poor vacuum

Question
Hi. Own a 1973 CB 350 and I am having trouble figuring out why I have to have the choke fully engaged in order for the bike to run. It will not run well if I engage the throttle to its max. At first I thought it was the ignition but have given it a tune up and still the problem is there. There doesn't appear to be any rips or tears in the carb diaphragms. I'm lost from there. Can you give me any suggestions as to what the heck the problem is
Signed, Boyd.

Answer
Boyd,

Also, check out these websites:
http://oldmanhonda.com/MC/interactiveMC.html
http://oldmanhonda.com/MC/wiring.html
http://oldmanhonda.com/MC/Rtiming.html


if it needs the choke to run then it is
either a lack of fuel or too much air leaking
into the intake.

-Make sure your gas tap has a good flow of fuel
to the carbs.

-Check the carb jets for plugging, the
main jet and other small jets and tubes
can plug very easily.
A good soak in some carb cleaner and then
physically checking all the jets is a good idea.
The main jet controls 3/4 to full throttle fuel.

-check around the carb intake tubes or flanges
for leaks, you can use carb cleaner spray or
wd40. It will speed up if it is leaking air.

-Loose or leaking exhaust gaskets can also
lean out the fuel mixture.

-is your camshaft tight on the points end?
if it wiggles the points will too, causing
a misfire.

-low compression can cause poor vacuum as well,
making it hard for the engine to draw fuel in.


http://www.dansmc.com/carbs.htm