ballpark wrote:

Hi,

I will try to explain the priming system up to the point where I am not
sure what it does anymore. The bulb is located on the side of the air
filter mounting plate. When you push it the air moves down a cone and
then runs though a small channel around the top of the carb inlet. The
channel is half made by a groove in the air filter, and it is enclosed
by the gasket that fits between the air filter mount and the carb.
Then the air comes out a small hole, and goes into a small hole with
about a 1mm diameter in the side wall of the carb intake mount. Here
is where I get lost. It's hard to follow the internal channels of the
carb. There are 2 holes pointing back at the air filter that I think
have something to do with it. One is large at about 3mm diameter and
the other is very small, closer to .001 of an inch.

When I cleaned the carb I disassembled every thing I could and actually
washed it in a water/soap bath. I used an old toothbrush to clean all
the crevices. I also used a small wire and ran it though all the
passages I could find. I didn't really see any crud come out. I would
also note the the carb, before I cleaned it looked fairly clean. I
then rebuilt the carb using new o-rings and gaskets. Everything was
clean and dry when i put it back together. One thing I didn't remove
was the half circle plug on the underside of the carb. I didn't know
its purpose and didn't want to mess it up.

As for the intake, its all plastic. I removed the bulb and thoroughly
cleaned the channel.

The bulb itself appears to be blowing the appropriate amount of air. I
think that I can also feel air come out of the 2 small holes I earlier
described. It's like it just not picking up any gas.

I think if I understood the theory on how the primer was suposed to
work, then that would help. Like, when priming, what hole should the
gas come out of? Are there any ball valves that could be missing?
Thanks again
-Brian



Serendipitously, on another newsgroup I haunt (rec.crafts.metalworking)
the same question came up and I'll paste the poster's explanation of how
the primer bulb system works he

*******************************************

The float controls the level of gas in the float bowl, most carbs have a
small air inlet to keep it from air locking. On the primer bulb models,
this air inlet is hooked to the primer bulb. When you squeeze the bulb
the air pressure forces the gas down in the float bowl, and up into the
main needle, dumps raw gas into the carb throat. As soon as you remove
the pressure, the float needle opens a bit to replace the gas that was
pushed out. Radically simple.


******************************************

Now, that makes elegant sense to me on a carburetor with a float bowl,
and that hole you mentioned in the center of the bulb may well provide
the bowl vent.

So, take off from that point and see if you can figure out why the
primer isn't doing it's thing. If it's supposed to work on the principle
described above, then I'd have to assume that there's a leak from the
carb bowl to atmosphere preventing pressure from building up and pushing
gas out the main needle valve. Try

But some carbs which mount right onto the fuel tank also use primer
bulbs, and those must work on some other system. Maybe there's just a
couple of little ball check valves which facilitate the pumping action.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."