A drastic reduction in fuel to air ratio within the carburetor is the primary reason why a snowmobile won’t run unless you put it on choke or half choke. The fuel air mixture will need to be fixed to run the snowmobile with the choke off.
You don’t need to panic if your snowmobile runs only on choke or half choke because there are some steps that you can take to fix the problem. You will find these steps in this article, as you read on.
Steps to Troubleshoot Snowmobile
Follow all the steps below to make your snowmobile run without choke or half choke.
Check fuel line
If the fuel line becomes blocked or damaged, enough fuel won’t reach the carburetor, so the fuel to air ratio will be low. You should unclog the fuel line or replace it if necessary to allow enough fuel to reach the carburetor. Here is how you should check whether the fuel line is blocked or damaged.
Remove the hood that covers the engine and inspect the fuel line. You don’t necessarily have to change the fuel line If it is clogged or collapsed. You can easily unclog the fuel line and straighten up collapsed parts.
Remove the fuel line and try passing fuel through it. Clear blockages with pipe cleaner tools or an air compressor.
However, if the fuel line cracks or splits, you must replace it with a new one. After you have solved all the fuel line issues, you should start the snowmobile and observe whether it runs without choke.
If the line is clean but not enough fuel is moving from the tank, it could be the fuel filter.
Check the fuel filter
A fuel filter’s function is to screen out dirt from fuel, but if the filter becomes too dirty, it will hinder the free flow of fuel. So if your snowmobile runs only on choke or half choke, it would help if you check the fuel filter.
To verify whether the fuel filter is dirty, you should trace the fuel line until you get to the area where the fuel filter is located. The filter is usually on the fuel line somewhere.
After you have spotted the fuel filter, inspect it carefully. If it appears too dirty, then you have to change it. Fortunately, a fuel filter is cheap and easy to replace. Follow the steps below to replace a dirty fuel filter with a new one.
I recommend checking out these Snowmobile Fuel Filters (link to Amazon), they usually have the best deals and can get them to you quickly.
- Start by removing the clamps that hold the old fuel filter to the hose.
- After that, you should pull the fuel filter out of the fuel line.
- Clean the area where you just removed the old filter and get a new filter ready for installation.
- Take the new filter and fix it into the ends of the hose.
- Make sure you observe the arrow’s direction on the fuel filter before you fix it into the hose.
Every fuel filter has an arrow that indicates the direction of fuel flow. Allow the arrow to point towards the carburetor while you are installing it.
You can cut off a short length from each end of the hose if the ends are too slack for the new filter. After you have fixed the new filter into the hose, you should clip it with a clamp.
For safety purposes, ensure you stay away from all heat sources while you are replacing the fuel filter. Once you have carried out the installation steps above, you should start the engine and observe whether fuel isn’t leaking around the new filter regions.
And of course, you should attempt to run the engine without choke to see whether the new fuel filter solves the problem.
Here’s a video showing how to replace the fuel filter and fuel lines:
If your snowmobile still requires choke or half choke to run, then you should proceed to the step below.
Adjust the Air-Fuel Mixture Screw
When you engage your snowmobile’s choke, it regulates the mixture of air and fuel within the carburetor. While the choke regulation is important, you can make the carburetor not to depend solely on it by setting the air-fuel mixture screw correctly. You will need a screwdriver for this adjustment.
Here is how you can adjust the air fuel screw within minutes.
- Remove the part of the snowmobile that covers the carburetor.
- Look for screws on the carburetor’s side.
- Please don’t loosen any screw underneath the carburetor.
- The screw underneath it keep the throttle plate air-tight.
- Usually, the air fuel screw will be on the side of the carburetor where you can adjust it without detaching the carburetor from the engine.
A person who isn’t familiar with carburetor’s parts may find it hard to differentiate the air fuel screw from the idle screw since the two screws are always on the same side. Here is the major difference between these two screws.
The air fuel screw is smaller than the idle screw. Once you have identified the right screw, you should use a screwdriver to adjust it.
If you tighten the screw, more fuel will flow into the carburetor, but if you loosen the screw, only a little fuel will flow into the carburetor.
Since the goal here is to increase the fuel that flows into the carburetor, then you need to tighten the screw. It would be best if you tightened it gradually because an excess fuel flow into the carburetor can create a different problem.
We recommend that you turn the screw only by a quarter turn. Start the snowmobile after each turn and observe whether it can run without choke. If it still requires choke, you should add an extra quarter turn and observe once again.
The snowmobile will run without choke when you eventually reach the optimum adjustment level. In case the problem persists after several adjustments, then you should proceed to the step below.
Here’s a video showing how to clean a carburetor if you feel like going all out since you’ll be messing with it anyway:
Adjust the Idle Screw
The idle screw also plays a role in the mixture of air and fuel, especially at idle speed. Just like the air fuel screw, you can easily adjust the idle screw until your snowmobile runs without choke. Open up the hood that covers the engine. Locate the idle screw just like you located the air fuel screw.
The idle screw is bigger than the air fuel screw, so make sure you adjust the right screw. Usually, the idle screw will be very close to the choke. After you have identified the idle screw, pick up your screwdriver, and adjust the screw gradually.
Here is a fast adjustment technic that can help you save a lot of time.
- Turn the screw counter-clockwise so that the rpm reduces at first.
- After that, you should start the snowmobile while gradually turning the screw clockwise until the snowmobile can run without choke.
- Most of the time, you will have to adjust the screw more than once before the problem is solved.
If the issue persists after numerous adjustments, you should carry out the steps below.
Check fuel pump
The fuel pumps forces fuel to flow through the fuel line, so if it becomes damaged, fuel won’t flow well. Fuel contaminant is the primary cause of fuel pump damage.
To verify whether the fuel pump in your snowmobile is still functional, you should follow these steps.
- Remove the hood that covers the engine.
- After that, you should detach the hose supplies fuel to the pump.
- Connect a vacuum gauge to the pump’s inlet and pull the starter cord.
- See what the gauge reads when after you pull the starter cord.
- If the gauge records a vacuum, it means the pump still draws fuel through its inlet when the snowmobile is running.
- Now that you have checked the pump’s inlet, you still need to check its outlet.
To check the outlet, you should remove the hose that connects the pump to the carburetor. After that, you should connect the vacuum gauge to the pump’s outlet. Pull the starter cord again and observe what the gauge reads.
If the gauge reads a high pressure, it means that the pump still supplies fuel to the carburetor when the snowmobile is running.
You should replace the fuel pump if the test above reveals that it is damaged. Before you replace the fuel pump, you need to take some precautions. Ensure you stay away from all heat sources. Ensure your surrounding has good ventilations. Wear gloves and safety goggles.
After you have taken every necessary precaution, you should follow these steps in order to replace the pump.
- Start by draining the fuel in the tank.
- After that, you should remove the hose that supplies fuel to the pump.
- Also remove the hose that carries fuel to the carburetor.
- Loosen all the bolts that hold the fuel pump to engine.
- Bring out the old fuel pump and insert the new one.
- Use bolts to fasten the new fuel pump to the engine.
- Connect the fuel pump’s inlet to the fuel tank using a hose.
- Also connect the pump’s outlet to the carburetor.
- Use clamps to hold the hose tightly to the pump’s inlet and outlet.
- Restore fuel into the tank and watch out for fuel leakage.
Start the snowmobile if fuel isn’t leaking at any region. Observe whether the snowmobile runs without choke.
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