Below you will find questions that users have asked about the Rochester 1 barrel carburetor. The questions are followed by our best guess answer. We say best guess, because we don't have the carburetor in front of us and users often leave out important information.
If you aren't sure about tackling this sort of job, then take it to a machine shop. They can usually do it.
Backfiring can be caused from lack of fuel also.
Minor dents and dings in a float are ok, but if you have a major dent, then replace the float. Floats are designed for use up a certain amount of volume. A big dent would change this.
Hesitation when you press the gas indicates you probably have a problem in the accelerator pump circuit. There are a couple of holes in the carburetor throat. Look down the carburetor and you will see them about 1/2 way down in a tube that goes across the carburetor throat. You need to be sure these are clear. You should see fuel squirting from these when pumping the gas.
The largest steel ball goes in the main discharge under the spring and the T.
The small aluminum check ball goes in the bottom of the accelerator pump well (not all carburetors need this).
The other small steel ball goes in the power post, then the small spring and then the cap.
My carburetor is missing the vent assembly on the top of the carburetor. Can I plug it off?
Not a good idea. Perhaps you can adapt something so that it is vented at all times, but keeps the gas from splashing out. Do this until you can find a parts carburetor.
Your problem is either the distributor advance not advancing, or the accelerator pump circuit has a problem. I will only address the possible carburetor problem.
Incorrect check ball placement. See above to determine which goes where.
Clean out the small passage in the tube that goes across the inside of the carburetor throat about half way down. Thin wire should do the trick.Fuel will squirt from here when the accelerator is pressed.
The passage from the accelerator pump well to the main discharge may be plugged. Blow air through it to check. You can also put some fluid in the pump well, then press down on the accelerator pump. Fluid should come out of the main discharge.
Put some fluid in the pump well and press down on the pump. Fluid should come out of the main discharge hole.
The main discharge uses the biggest steel ball, then the spring, then the T.
This is the round shaft type of Rochester B accelerator pump assembly. The return spring 66-15 goes in the well 1st. The delayer spring 67-3 (trim to size) goes over the shaft. The bracket is next, then a retainer clip, which can be a simple C clip. holds it together.
Also of note is that this is a leather pump and will need to be replaced with a complete pump. You won't find this in many of the 1 barrels, but does comes along once in a while. Kits only include a rubber replacement cup which will not work on this pump.
To replace the pump measure the overall length and compare with our 2 different pumps.
A last ditch effort would be to put 2 gaskets on the float bowl. That will sometimes do it.
I now have a couple Rochester B and one carb the throttle linkage on the throttle shaft is lose and the end of the shaft is peened over. I thought this peening was a shade tree repair for the other carb’s throttle shaft has a screw to hold the linkage in place. I was getting ready to turn a new shaft with threads & screw to hold the throttle linkage.
Well because of the video I found that the peening of the shaft is factory. Who would think?
Another method would be to braze the end.
Could be a weak fuel pump - test the pressure and compare with the specifications in your motor manual. Around 4 lbs.
Power piston not working correctly.
In the power cap there should be a check ball with a spring on top.
Make sure the power piston moves up and down without restriction.
There should be a return spring under the power piston.
Could be a couple of things.
The 1 barrel body might be warped, which is common these days. They are too old. Fuel might be dumping over into the carburetor bore temporally flooding it.
The float level may be off enough that when on a hill it makes a difference.
Our experience with the 1 barrel would point to the 1st option.
Carburetor Floods When Stopping, Turning, or on a Hill
This is most likely caused from a warped float bowl as almost all of the Rochester B's are.
- Engineer a jig to clamp the carburetor in a vise and heat it up. Tighten the vise, let cool and check for warpage.
- Adding a 2nd float bowl gasket might help, but is not a lasting solution.
- Replace the carburetor with our N228 new carburetor.
Some of the things causing too much fuel to enter the carburetor.
1. Bad float, or float adjustment bad. Test the float by heating up some water and immersing the float. Any bubbles indicates a leak.
2. Needle & Seat not sealing. Turn the top upside down so that the float rests on the needle. Blow gently into the fuel inlet. You should not be able to blow by the needle & seat. Keep in mind that blowing over 4 - 4.5 lbs will cause the needle to open.
3. Fuel pump pressure. Should test 4 - 4.5 lbs. Higher pressure will force the needle open, letting gas go by. New fuel pumps are especially suspect. If all else fails add a regulator between the pump and the carburetor.
4. Dirty carburetor. Pull the top off of the carburetor. Any dirt, or corrosion at the bottom of the bowl indicates a dirty carburetor. Clean & rebuild the carburetor.
5. Power piston may be frozen, allowing fuel to flow through even at idle. You should be able to move the piston up and down freely.
6. Check ball, or spring may be missing from the power cap. The small check ball, then spring goes in the hole before screwing in the retainer screw.
Watch the video below for tips on what to look for when your carburetor is flooding.
- Engine problem such as bad valve.
- Electrical problem - plugs, wires, points, etc.
- Lack of fuel - Weak fuel pump. Float valve sticking.
- After sitting for several months the gas may have turned varnishing the inside of the carburetor. That will cause passages to be plugged.
- Dirty carburetor, clogging passages and restricting gas flow.
- Check the float level. Both pontoons must be the same height and centered in the float bowl.
- Move the float up & down by hand to feel any catching.
- Test the fuel pump. Around 4 lbs will do it. New pumps are especially suspect.
- At idle look down the carburetor to see if gas is dribbling from the main discharge. The discharge check ball might be leaking, or the spring isn't on top of the check ball.
- Is the choke valve open completely when the engine is at operating temperature? Obviously this is the hot air, or electric type of choke.
- Be sure your gas cap is vented. After a long run, remove the gas cap. If you get air rushing in/out you have the wrong cap on it.
- Check the idle vents to see if they are plugged. Refer to our Rochester B manual to see where the idle bleeds are located.