Why Does My Dirt Bike Only Run on Choke


why does my dirt bike run on choke

Having been excited to get my second-hand motocross, I was so anxious to take it out on the road and ride it. After starting up the engine on choke mode, everything seemed fine. However, as I was riding my new dirt bike, I happened to turn the choke mode off, and the engine immediately died.

I was astounded that the new bike decided to stop working just after I had purchased it with so much excitement. Therefore, I had to ask my local motocross dealer, why does my dirt bike only run on choke?

The following was the diagnosis he gave me on my newly acquired second-hand dirt bike.

Clogged Pilot Jet

Dirt bikes that only run on choke mode are a sign of a fully or partially clogged pilot jet.

After some time, it is clear that fuel may go bad; therefore, the first jet may get clogged with the fuel that is varnished up in the pilot jet.

Another reason is that the circuit may deliver fuel in the idle mode, which means it makes use of the smallest passages that you have in your carburetor.

However, no liquid that is poured into your gas to clean it up. The only solution is to take the carburetor apart and clean up all the parts.

How to Clean Up Your Dirt Bike Carburetor

As mentioned, the only way to fix your bike from going off when it is not using the choke valve is to clean the carburetor.

There are different ways to make this possible. They include the following.

Clean spray

The clean spray is the easiest way, to begin with, the removal of the clogged jet in your motor cross bikes carburetor.

Products to use include Berryman Chemtool. You can buy this one from Amazon by using this link.

However, if you are looking for a stronger spray, you can use Berryman Chemdip. (This link will direct you to Amazon where you can buy this product)

This is used for soaking parts of your engine. Additional methods you can use include Ultrasonic cleaning and soda blast.

Carburetor Tuning

When your motor cross bike is back to its excellent operation, what you need to do is use an idle mixture to tune the engine.

Your carburetor has a fuel or air screw that you can use to optimize how it feels when it is idle.

By using this screw, you can regulate the tune mode to a tone that you find appealing for your motor cross bike.

Once you have completed this process, your dirt bike does not have to run on choke alone. Your engine will not go off when you are not on choke mode.

It is normal that when your dirt bike is running on choke mode, you use very high RPMs.

This means that you are also using up a lot of fuel. By adjusting the screw that controls air and fuel in your carburetor, you reduce the consumption of fuel on your dirt bike. 

Does Cleaning the Carburetor Always Work?

It is important to note that for dirt bikes, the above information to clean the carburetor does not always work.

Most bikes will only operate on choke. Once the choke valve is turned off, no amount of gas will help your dirt bike to move as the engine sputters down and dies.

In such cases, seek a new carburetor altogether. Choose one that is compatible with the dirt bike model that you have.

Another option is to warm up the bike with the choke on and then turn the choke off.

Doing so allows your motor cross bike to run with the choke off saving you fuel and keeping your engine in good condition.

Nonetheless, this does not work with most dirt bikes models as some still require the choke valve open to operate well.

The Reason Why Your Dirt Bike Will Only Run with the Choke Valve On

 The main reason why a dirt bike only runs when the choke is on is that the primary circuit is running lean. There could be an air leak or some clog in it. 

If you cleaned the carburetor, but the choke valve must be on to run your bike in, it means you may not have done the job correctly.

There are those parts of the valves in the carburetor that need cleaning but will not get cleaned well as you are not able to see or get to these parts.

Therefore, you need to take apart the carburetor to get to the jets and soak it in a solvent for over 5 hours before having to blow out the air passages using high pressure.

Note that the solvent that is used to clean is strong.

Therefore, you need to remove any O-rings or gaskets as the solvent may destroy them.

This is another reason why some dirt bikes will still need to run with choke on due to the damaged carburetor parts.

Remove these parts before soaking the carburetor in the solvent.

Unused Dirt Bike

If you have not used your bike for some time, it will most likely only run with choke on.

Evaporating gas tends to gum up the parts leading to the inability to run your bike when the choke valve is off.

Should you leave the gas valve on, your entire tank will evaporate and block all valves from the carburetor if you have not used the bike for some time.

Secondly, it is not enough to turn your motor cross bike on for a few minutes once in a month when not in use.

You need to ensure you ride the bike in to clean the air valves and flash your carburetor out.

Mostly, these are some of the things you need to consider to ensure that your bike will not run on choke all the time you need to use it for your enjoyment or a leisurely ride.

Conclusion

In conclusion, most dirt bike owners are forced to use their bikes while the choke is on due to proper maintenance.

A well-maintained dirt bike that is not left to stay unused will always operate well even when the choke valve is off.

Ensure you read through various forums to ensure you have enough advice to keep your bike in tip-top shape and functional when the choke valve is off.

Doing so will save you the cost of maintenance for your motor cross bike and the cost of fuel use when the choke valve is on when riding your bike.

Daniel Mose

Daniel is a big fan of dirt biking. I own KTM 250 SX-F. I love learning how to maintain this dirt bike and ensure it lasts long while serving me without any issues. Join me in this journey as I document stuff that we, as dirt bike lovers, ought to know.

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