Acceleration problems

backyard

83 columbia par car with Walbro WHL-11 carb.

If I ease (real easy) the accelerator on, the engine will rev up but if I do it fast the engine cuts back before it even revs up. It almost seems like its being governed by the carb but there is no governor. I can use the choke and it helps.

When I pull a hill it doesnt want to because I can't mash the gas slow enough. I have to adjust the choke to climb it slowly. When I go down a hill it does real good but with some choke.

I've adjusted the idle needle all the way up to 4 turns, same thing. Doesn't matter where I adust the idle needle to, it is the same.

I've taken the carb off three times and inspected it. All passages are free, bowl is clean, under the welch plugs are clean, carb cleaner comes out all holes. The hole for the choke shaft is oblong so it definately has been used.

I don't know what else to do or try except buy a new carburetor and try it since I think the carb is at fault. Anyone have any suggestions?

BGW

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CharleyL

I know very little about Walbro carburetors, but the description of your problem sounds to me like the accelerator pump (if it has one) is not functioning. With the engine not running, look down the throat of the carburetor and press the accelerator, or operate the accelerator linkage. You should see a squirt of liquid fuel enter the carburetor throat from a tiny hole located down near the butterfly plates. If you do not see this squirt of fuel your accelerator pump is not working or this tiny hole is plugged. Sometimes a single strand of a piece of copper wire can be used to clean out this port by pushing it carefully through with the carburetor off the engine and totally apart. The accelerator pump itself
is a chamber similar to the float bowl chamber, but it's usually located off to the side of the float chamber. It will have a rubber bellows diaphram and a linkage from the throttle
to depress the center of this rubber diaphram as the throttle is opened.

I hope this helps.

Charley

backyard

The earlier, pre 82 models had the tillotson carbs that has the pump you describe, but mine is a float bowl carb. I have a standalone three line pump feeding the carb.

I have cleaned a few carbs in my day and I've never seen anything like this. float is adjusted, float needle works properly, compression is 100 psi, muffler is not clogged, and new crank seals. I feel what seems to be plenty of pressure/vacuum from the line feeding the pump.

I have ordered a new carb so I'll just try it when it gets here. I am going to gravity feed the carb and see if that makes a difference.

CharleyL

My 1987 Cushman Truckster has a Keihin carburetor. It has a float bowl, but off to the side there is another smaller chamber that is the accelerator pump. My Truckster sat in a pine forest for over 12 years before I got it, so almost everything needed rebuilding. When I first rebuilt the carb it took me about an hour, just working on the internal passages, to get them clean enough for the accelerator pump to work properly again. I used carb cleaner and some single strands from #20 ga electrical wire pushed through each passage several times to get them clear so the accelerator pump would work again. I actually got the carburetor working while I was waiting for the rebuild parts for it, but it ran much better after replacing the rubber parts, the float needle valve, the accelerator pump diaphram, and the float (old plastic floats don't usually float at the same level as a new float).

The original fuel pump on my Truckster was way beyond saving and the only replacements that I could find were NOS with crumbling old rubber parts and excessively high ($140) price tags, so I ended up installing an automotive electric fuel pump from ORiley Auto Parts. This pump has an integral pressure regulator, so no bypass filters, regulators, or additional hoses are required for it. A line direct from the tank, through a filter and to the fuel pump, then a second line from the fuel pump direct to the carburetor is all of the plumbing that is necessary. Then a wire from the ignition switch or any place that has power when the key switch is "on" connects to the red wire of the pump. The black wire from the pump connects to the frame. It's that simple. I removed the old mechanical fuel pump and made up a plate and gasket to seal up the hole where it was attached, but the old fuel pump could have remained in place and unconnected as long as the gasket doesn't leak.

Charley

backyard

The new carb fixed the problem. I believe somewhere in the main jet is partially clogged although it will shoot carb cleaner through it. I may try boiling it later on.

CharleyL

Glad you fixed the cart, but too bad that it took a new carburetor when the problem is very likely just a bit of dirt in the wrong tiny place. Maybe comparing the new and old will help you find where the problem is so you can have a spare on the shelf.

Charley