Your motorcycle is not running unless you start it with a choke, is it?
Or worse, you have to keep the choke on the entire time you are riding your motorcycle?
Without an open choke, is your bike not starting or not running at all?
The main reason why your motorcycle is not running without a choke is because of clogged petcock, fuel lines, fuel filters, or pilot jet of the carburetor.
Cleaning the dirt in these parts should solve the issue. Other possible reasons can be dirt in air filters or air leakages.
If it is only the starting problem, i.e., you need to start the bike with the choke but can close it after you have started the motorcycle, then it is not a big concern.
Cold weather or the motorcycle sitting idle for a long time can cause cold starting problems.
But, on the other hand, if you need to keep the choke open for the entire ride and the motorcycle pretty much dies on you as soon as you close the choke, then we need to seriously look into the problem.
Even if you need to start with a choke frequently, it is better to diagnose the problem so that the issue does not escalate.
Now, let’s investigate the reasons why your motorcycle is not running without the choke in detail.
Reasons why the motorcycle won’t run without the choke
The 2 main reasons for a motorcycle to only start or run with the choke on – are either because of problems in the airflow or because of the fuel flow.
Let’s discuss each one by one.
Reason #1: Problems in the air flow
Although the number of cases with issues in the airflow to the engine is low, it is always better to check them just to be sure.
Here, the air-fuel mixture entering the engine is important for the motorcycle to run.
So, if the air entering the engine is not sufficient enough, then we have the problem of our motorcycle dying out on us.
The most common situation is the bike starts spluttering and eventually comes to a halt.
For this exact reason, we need to check the air filters and make sure that the filters are clean.
If you feel there is too much dirt in the filter and not sufficient air is entering the engine, then it is time clean the filters or better, replace them with a new one.
Reason #2: Problems in Fuel flow
Fuel flow issues are the main cause whenever the bike only runs with the choke on.
Again, as mentioned earlier, the air-fuel mixture entering the engine system is very important for the motorcycle to run smoothly.
Any deviations or problems in the sufficient fuel flow to the system, the problems are bound to arise.
Okay, I got the theory. So where do I need to check?
Well, the entire fuel flow system.
The petcock, the fuel lines, the fuel filter, and of course, the dreaded carburetor.
Specifically, the carburetor since it is the main culprit in most of the cases.
If your motorcycle uses a fuel injection system, then this case won’t be applicable to you as there will be no carburetor in your motorcycle.
But if your motorcycle uses a carburetor for fuel supply, these parts need to be examined.
Any dirt in these parts – petcock, fuel line, fuel filter, pilot jets – will prevent the entry of sufficient fuel into the engine system.
How does the choke help here?
The choke is a mechanical lever that provides a rich fuel mixture to the engine when pulled out.
So, whenever you need a rich air-fuel mixture in the engine, you can pull the choke.
In this case, when your motorcycle is having starting troubles, switching the choke on – makes the engine receive a rich fuel mixture.
As a result, the engine combusts the mixture easily.
Thus starting the engine, and hence the bike.
Chokes are especially helpful during cold starts. It helps the motorcycle to start easily.
Here are the solutions for when the motorcycle won’t start without the choke on:
#1. Check the air filter
First and foremost, make sure it is NOT an air-flow problem.
Check your air filters first.
If the air filter is filled with dirt, not enough air can pass through. And the air-fuel mixture is just not right for your motorcycle to run smoothly.
If the air filter indeed turns out to be the issue, then clean up the dirt or if applicable, replace the filter with a new one.
However, most of the time when your motorcycle runs only with the choke open, it is not the air but the fuel flow that is causing the problem.
So, once you are thorough with the air filters, it is time to check the fuel flow passage.
#2. Inspect the fuel pipe, petcock, and fuel filter
Now we come to the fuel flow problems. Which is the most likely reason.
Dirt in the petcock, clogged fuel lines, and dirty fuel filters can all be the reasons why your motorcycle only runs on choke.
Let’s start examining them one by one:
First, check the fuel lining.
The fuel pipe flows from the tank to the petcock to the carburetor.
Take out the pipe connecting the petcock (reserve fuel switch) to the carburetor.
Of course, turn the fuel petcock OFF before.
The fuel should flow out of the pipe.
If yes, the fuel pipe is working fine.
Repeat the same with the pipe coming from the tank through the filter then to the petcock.
If there is a problem, either the fuel pipe is bad, or there is something wrong with the connecting part – the fuel filter or the petcock.
Petcock (reserve fuel switch) controls the fuel flow from the gas tank to the carburetor.
Check if the petcock switch is working fine.
Take out the fuel pipe connecting the carburetor.
Now change the switch.
When the petcock is OFF, no fuel should flow out from the pipe.
And when the petcock is ON or on RES (reserve), the fuel must flow out of the pipe.
If not, petcock is the culprit.
And you must change it.
The fuel filter is located right below the gas tank.
Try to remember when was the last time you replaced the fuel filter on your motorcycle.
If you cant remember, then you must replace it.
Now, take out the fuel filter.
And check its condition.
If the paper plates are dirty and blackened, you must replace the filter.
If it is in good condition, we move onto the next solution.
#3. Clean the pilot jets and tune the carburetor
Clogged pilot jets are the most common culprit whenever your bike only runs with the choke on.
Another possible reason is carburetor is not tuned right.
You have to take the carburetor out of the system for this.
If you feel disassembling and reassembling your carburetor is a herculean task, outsource this task to your mechanic.
However, if you are sure about getting your hands dirty, well get down to it then.
Here are some tips for you while you are cleaning the carburetor.
- Note the make and model of your carburetor and the motorcycle before disassembling.
- Keep the appropriate carburetor kit ready with you for a smooth cleaning and reassembling.
- Nuts and Bolts – organize them properly. The rust on the parts makes them impossible to interchange.
- Clean them with carburetor solution
- Air hoses can be handy.
- Adjust the pilot jets first while reassembling.
Be gentle while cleaning up the pilot jets and the fuel lines.
For a detailed roundup, here are the steps to clean the pilot jet of your carburetor.
For carburetor tuning, you can refer to the video here.
You need to be careful not to scratch or damage the inner lines.
Also, never ever use a wire to clean the pilot jet. Always blow air into the jet for cleaning.
For cleaning the carb, using a solution to clean is the best way to go about it.
- The main reason why your motorcycle is not running without the choke on is because the engine is not getting the right air-fuel mixture for its intake.
- For air flow problems, check your air filter. Most likely, it is clogged or there is too much dirt on it.
- If yes, clean the dirt, or better, replace your air filter with a new one.
- Another problem causing air flow issues could be air leakage. Check for the rubber bladder and pipes for any leakages.
- If it is not the air-flow problem, then the fuel is not being supplied sufficiently to the engine. And that’s why, choke needs to be switched on to pump in more fuel.
- Fuel flow problems can be because of dirt in the petcock, fuel line, fuel filter, pilot jets, and carburetor. Any clogging in these parts can deter the fuel flow to the engine.
- So, remove and disassemble your carburetor and clean the pilot jets, fuel lines, filter, and the carb – with a carburetor solution and an air hose.
- Reassemble the carburetor on your motorcycle. Lo and behold, you don’t need the choke anymore to run your motorcycle.
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