Accelerator Pump Diaphragm Relief Hole

The hole at the bottom of the pump diaphragm cover is a relief hole. Any fuel coming out of this hole indicates the diaphragm is bad and should be replaced.

The other hole just below the pump diaphragm is a relief hole for the power valve. Any fuel coming out of this hole indicates the power valve is leaking. Not all 2150 carburetors have this hole.

Notice the deep cover over the power valve. This indicates this carburetor has a 2 stage power valve.

TROUBLESHOOTING

You press on the gas pedal and the engine seems to bog down. What to do?

1st let me say that there are issues besides the carburetor that can make this happen, but since I'm in the carburetor business, I will assume everything else has been taken care of and concentrate on the carburetor. Also I will assume the carburetor has been rebuilt. If not, then that is where I would start.

Most likely this problem lies in the accelerator circuit. Here are some things to look for.

• Make sure the return spring is between the accelerator pump diaphragm and the carburetor body.
• Is the red umbrella check valve installed and the big end is on the pump diaphragm side?
• Check the check weight in the main discharge. This is the middle hole under the venturi cluster. The check ball goes 1st, then the check weight. You can check the check ball to see if is is sealing by holding the check ball down (use a brass drift punch), and operating the throttle. You should feel some pressure because holding down the check ball is sealing the main discharge. If you suspect the ball isn't sealing, then use a brass drift punch to tap on the ball a few times, which will help form the hole around the check ball.
• Using thin wire, run through all of the small holes and passage ways. Ethanol will leave deposits behind that normal cleaning will not get out. Pay special attention to the venturi cluster. There are some very small passageways in this assembly and it is very common for them to get plugged up.

After all of this is done add some mineral spirits to the float bowl and operate the accelerator pump. You should see fluid come up through the main discharge (where the check ball and weight is). Replace the venturi cluster and operate the pump again. You should get a fairly strong stream of fluid out of both sides of the venturi.

Do all as mentioned here and you should be able to eliminate your hesitation problem, or at least eliminate the accelerator pump circuit as the cause.