Penton 125cc Bing Carburator Problem

[pklinck]

I have a just restored 73' sachs B engine in a cmf penton motorcycle. I have one problem with the 27mm Bing carburator.

 When I push the tickeler down the gas does not run from the tank (or funnel) down the gas line into the carb.  In fact, the fuel does not run into the carb when allowed at all (from the tank or by a funnel, which it did).  However, in the process of removing, loosening or cracking opening the float bowl a little for air, the liquid will imediately fill up the bowl.  then when fastening the mechanically filled bowl the bike starts and runs great until the bowl is then emptied again.

I cleaned, to the best of my knowledge, the carb, jets, etc. using carb cleaner and air.  Since it runs fine once there is fuel in the carb, i don't believe there is a jet issue....  I put in the standard jetting as recommended.  The needle and jet needle (2.73)were replaced as a matching pair.

Do I have an orfic in the carb or air breather which is plugged which prevents the carb from filling up?  Which one or others which can influence the situation?  THE FLOAT BOWL VALVE IS ALSO NOT STUCK I believe but i did not buy a new one.    Any suggestions or comments?

peter klinck

[DKWRACER]

For fuel flow problems, you could chuck the carb in a vice,with the fuel bowl off, rig up a remote fuel source, then move the float up/down to simulate normal float operation, can also depress the plunger to simulate fuel flow when the plunger pushes down on the float, maybe a float height issue...adios, keep us posted,  Tom Brosius

[Kip Kern]

Check the float needle, and bowl vent tube in the bottom of the bowl.  Blow out every orfice in the carb body and check the choke seat to make sure there is one there and the circuit isn't plugged.

[joe novak]

Also open the gas cap...  There is a vent hole in the gas cap; be sure that is not plugged.   I suggest you remove the fuel line from the carb, open the gas cap, then rotate the petcock lever to be sure the petcock is working properly, and gas will drain from the tank.    joe

[pklinck]

Joe,

It isn't the tank since I poured fuel doen through a funnel and gas line.  I like tom's and Kip's comments.  I will try to repeat the checking and cleaning processes again.  thanks

peter klinck

[Paul Danik]

Peter,

It sounds to me like a float level issue if as soon as the bowl is lowered the float needle drops enough to allow for fuel to flow.

Paul

[DKWRACER]

For fuel flow problems, you could chuck the carb in a vice,with the fuel bowl off, rig up a remote fuel source, then move the float up/down to simulate normal float operation, can also depress the plunger to simulate fuel flow when the plunger pushes down on the float, maybe a float height issue...adios, keep us posted,  Tom Brosius

[Kip Kern]

Check the float needle, and bowl vent tube in the bottom of the bowl.  Blow out every orfice in the carb body and check the choke seat to make sure there is one there and the circuit isn't plugged.

[joe novak]

Also open the gas cap...  There is a vent hole in the gas cap; be sure that is not plugged.   I suggest you remove the fuel line from the carb, open the gas cap, then rotate the petcock lever to be sure the petcock is working properly, and gas will drain from the tank.    joe

[pklinck]

Joe,

It isn't the tank since I poured fuel doen through a funnel and gas line.  I like tom's and Kip's comments.  I will try to repeat the checking and cleaning processes again.  thanks

peter klinck

[Paul Danik]

Peter,

It sounds to me like a float level issue if as soon as the bowl is lowered the float needle drops enough to allow for fuel to flow.

Paul

[pklinck]

Paul,

When the carb is empty, at the begining as i attempt to fill the carb from my funnel (since it is winter and i cannot leave gas in the tank for testing), The gas simply does not enter the carburator.  It only fills the line and not entering the carb.  But as I said, once you open the float bowl cover slightly, the gas immediately falls into tha basin and will flow out unless i close it again.  It is at this time that the motorcycle starts up and runs fine until the bowl becomes empty.....anymore comment As Kip/dwight, mentioned, Maybe the orfic underneath the choke slide could be blockes or the breather vent on the bowl is plugged?

peter klinck

[pklinck]

Paul,  what do you mena by a float level issue?  Damaged?  I adjusted it according to the manual...ie. turn carb upside down and the float level should be parallel to the bench....?

peter klinck

[gooddirt]

Check the vent passages to the float bowl, spray carb cleaner into them from inside the bowl it works better. blow the fuel down the gas line maybe a air lock in the line. can you hear bubbles in the bowl ?

[Paul Danik]

Peter,

  Fuel should begin to flow when the float is parallel while inverted. I always put a piece of fuel line on the carb and blew through it to test the proper setting, when the float is level the air flow should begin if you are lifting the float from its resting position while inverted.
If you want to eliminte the float as an issue, just assemble the carb without the float and needle, put it back on the cylinder properly and turn on the fuel, if it flows it is float related, if not it is a vent issue.  I don't think a vent issue would keep every drop of fuel from flowing, but I have been wrong before.

In reading the Penton manual on float adjustment, it states that the float needle ball must NOT be pressed down while the float is parallel, while inverted, that is the key. If the float sits level at rest, it is not properly adjusted.

Hope this helps.
Paul