Categories
Saunas

How to adjust idle on a motorcycle

Quick guide with pictures on how to change the idle speed on a motorcycle and why you might need to.

What is idle speed?

Idle speed is the rotational speed of the engine when decoupled from the drivetrain without any throttling being applied. This information is displayed on the rev counter next to the speedometer on both cars and motorcycles. The rev counter shows how many times the engine’s crankshaft makes a full rotation in a minute. The common term for it is RPM (revolutions per minute).

Adjusting the idle speed

When to adjust a motorcycle’s idle speed?

Idle speed must be adjusted when too low (the engine will keep stalling) or too high (causes engine wear and shortens its lifetime). Idle speed of a warmed up motorcycle engine should be between 1000 and 1500 rpm.

How to adjust a motorbike’s idle speed?

Wait for the engine to reach its normal operating temperature and do not adjust the idle speed while the choke is on as it gives inaccurate reading. Refer to the motorcycle’s manual, in this example the adjusment is made on a Suzuki SV650S, where the idle speed control is located on the left hand side below the tank. It is easily accessible and requires a phillips screwdriver only: rotate anticlockwise slowly to decrease or clockwise to increase idle rotational speed of the engine while observing the rev counter. Older motorcycles may require slightly higher rpms to prevent stalling while idle, but do no set it over 1500. That can indicate other problems that need to be looked at and repaired.

How to adjust idle on a motorcycleHow to adjust a motorcycle’s idle speed

Motorcycle chokes

Most modern motorcycles come with automatic chokes, which increase the RPM after igniting a cold engine to reach operating temperature quicker and prevent stalling. Manual chokes on bikes can be on the handlebar (which allows to start riding) or at the side around knee-height that makes it impossible (or very dangerous) to turn it off while riding. The choke shouldn’t be used in warm weather or left on too long in the cold (usually a few minutes is enough) as it causes unnecessary engine wear. Normal operating temperature of a motorcycle engine ranges between 70 and 105 Celsius.

Did you find this article helpful?

Help the site grow with more content to reach a wider audience while keeping it free!

How to adjust idle on a motorcycle

Your motorcycle relies on a proper mixture of air and fuel to power its motor. This mixture is governed by the carburetor, which pulls air into a channel called a venturi and mixes with gas before entering into the motor. At a standstill, the air must pass through a small opening between the throttle valve and the venturi, letting a small amount of the mixture into the motor and allowing the motorcycle to idle. At idle, the throttle valve is controlled by the carburetor’s idle screw, increasing or lowering idle speed by opening or closing the valve.

Step 1

Place your motorcycle in neutral and start the motor. Let the motor run for a few minutes to warm up. Once warm, take note of the motorcycle’s engine idle speed. Most motorcycles require an idle speed of 1,100 to 1,300 RPM (revolutions per minute) to operate properly at a standstill.

Step 2

Turn the idle screw slowly using a screwdriver, twisting the screw counter-clockwise to lower the motor’s RPM or clockwise to increase RPM. Stop adjusting the screw when the tachometer indicates the desired RPM range.

Twist the throttle open a few times and observe the tachometer needle as the RPMs fade. The needle should return to the desired idle speed. If not, readjust the idle and test it again.

A motorcycle idle level rarely changes from the standard setting. If your bike is idling high or low this indicates you may have something wrong. Lets go over a few things to check that might help your motorcycle idling issues.

How To Set The Idle

Many older motorcycles that use a carburetor to mix the air and fuel, set the idle with a simple stop screw. The screw prevents the throttle valves from closing completely, allowing fuel to consistently flow into the motor when you are off of the throttle. Just simply turn the screw in or out to adjust the idle. The screw is usually located on the carburetor near the choke. This same screw system is used on the first generation of fuel injected motorcycle engines.

How to adjust idle on a motorcycle

Newer models that have fuel injection systems have an ECU (Engine Control Unit) that controls the idle level. If your bike has an ECU you cannot adjust the idle easily. If your bike is idling poorly with an ECU then this points to a larger problem than simply adjusting your idle with a stop screw. My recommendation would be to take it to a shop and have it tuned by a professional.

How to adjust idle on a motorcycle

A motorcycle idle is usually set between 1000 and 1500 RPM when the engine has reached it’s operating temperature. While the bike is warming up the RPM can be a little higher than at operating temperature. The best idle speed really depends on the type of engine and air to fuel ratio. The best thing you can do to figure out what idle speed is best for your bike, is to search in the user manual. If you don’t have a physical copy, most can be googled and obtained digitally.

There is risk for running the motorcycle idle too low. This can cause low oil pressure and is a real risk. If you aren’t going to set your idle to the factory level then you should always aim for high idle speed over lower.

Motorcycle Idle Too Low

If your bike has been warmed up and is idling lower than the recommended level from the manufacturer, you probably have a couple of problems:

  1. The engine will stall easily or may not stay running without throttle being added. You will also experience stalling during take offs.
  2. The oil pressure in the engine will be very low

Here are some potential causes of those problems:

  • Idle Screw isn’t set properly or the ECU isn’t setup correctly. This is usually the first thing people check.
  • Too Lean Air to Fuel Ratio – stock bikes usually run slightly lean so if you do any modifications such as change the exhaust or air filter. This could result in more air flow than the stock parts and cause the motorcycle to run too lean. Check out my article on backfires that might answer some of your questions about air to fuel ratios.
  • Valves have too tight of a clearance.
  • Throttle Valves are not synced properly.
  • (TPS) Throttle Position Sensor is not adjusted properly.
  • Fuel tank Charcoal Canister is clogged by dirt or old fuel and isn’t allowing enough fuel to the carburetor.

Motorcycle Idle Too High

A motorcycle idle that is a little high is not dangerous for your bike but isn’t optimal either. However, if your bike is revving out, you should shut if off and attempt to resolve the issue or you could blow up the motor.

When your idle is high these are usually the problems you come across:

  • Louder than usual noise from the motor winding up to higher RPM.
  • You may hear a loud grind sound when you put the bike into gear because the RPM are too high even when you are off the throttle.

Here are some of the probable causes of your high RPM.

  • Idle Screw isn’t set properly or the ECU isn’t setup correctly. This is usually the first thing people check.
  • Your Oil Temperature Sensor or Water Temperature Sensor has gone bad.
  • Your throttle valves are not synced properly.
  • (TPS) Throttle Position Sensor is not adjusted properly.
  • Throttle Cable is jammed and will not allow the valves to close.
  • Cold Start Lever Cable is jammed and the valves cannot close.
  • You have a leak in your Intake Rubber Hoses which are between the cylinder head and the throttle valve housing.

If you haven’t noticed most of the problems causing high or low idle are the same for both issues.

Keep your air filter clean and don’t run bad gas. These are things that can lead to or cause idle issues. If your air filter is dirty then there will be dirt particles that will go through it and find their way into your injection system. Over time this could build up and cause a clog and you will find yourself spending a lot more time working on your bike than the time it takes to just clean the filter regularly. Regular maintenance is a huge part of being a rider and should become routine for you.

As those manufacturing factories set the appropriate idle for these motorbikes and control them electronically, the idle adjustment process is quite different from those previous motorbikes. When a bike possesses a carburetor, you can easily adjust idle speed according to your preference with an idle screw.

Can a flathead screwdriver be used to adjust the idle?

This is actually a simple task that requires only a flathead screwdriver, and you can properly adjust your idle in under 5 minutes, once your engine is warm. This process cannot help you repair problems with your engine, but it can help you keep your car from dying unexpectedly or running too hot, thereby accelerating engine wear.

What should the idle speed be on a Ford truck?

Repeat Step 4 and Step 5 as many times as necessary until the engine is idling at your desired speed. Lower the hood support arm, close the hood and turn off the truck’s engine. Under normal conditions, the truck’s engine idle speed should be about 800 RPMs.

How can I check the status of my Harley Davidson?

Motorcycle status: With H-D Connect service and the H-D App, the motorcycle owner will be able to check key vehicle health information on the H-D App at any time, from any location where sufficient cellular signal is available.

Where does the sidecar go on a motorcycle?

This means that the author is assuming that the sidecar is mounted on the left hand side of the motorcycle. Sidecars were born out of the motoring era of “transport poverty”. That is, it was the cheapest motorised transport to buy, operate and park – apart from a solo motorcycle.

How does H-D Connect work on a Harley Davidson?

H-D Connect service will send an alert to the owner’s phone if the security system is activated when the motorcycle has been bumped or is being tampered with.

Where is the adjustment wrench on a Harley Davidson?

You must first remove the seat to gain access to the adjustment wrench, however. Remove the rear seat screw and push forward and up to pop the seat off. The wrench is located on the bottom of the seat. Check your owners manual and use the wrench to adjust the shock accordingly. Then enjoy your new, even smoother ride!

As those manufacturing factories set the appropriate idle for these motorbikes and control them electronically, the idle adjustment process is quite different from those previous motorbikes. When a bike possesses a carburetor, you can easily adjust idle speed according to your preference with an idle screw.

Can you adjust the suspension on a Harley Davidson?

Harley-Davidson suspension characteristics have improved significantly over the last few decades. But of course, that doesn’t mean you can’t improve the ride quality of your bike even further. And while making suspension adjustments might seem a little intimidating at first, the job isn’t too hard.

Where is the shock adjuster on a Harley Davidson?

You must first remove the seat to gain access to the adjustment wrench, however. Remove the rear seat screw and push forward and up to pop the seat off. The wrench is located on the bottom of the seat. Check your owners manual and use the wrench to adjust the shock accordingly.

How do you fix a rich air fuel mixture on a motorcycle?

The 6 main ways to fix a motorcycle running rich are to:

  1. Adjust the air to fuel ratio.
  2. Check if the needle is sticking in the carburetor.
  3. Check for stuck open floats.
  4. Clean your air filter.
  5. Check for stuck open butterfly valves.
  6. Change your O2 sensors if your motorcycle has them.

How do you adjust a fuel mixture screw?

Here’s how you adjust them. Start the engine and let it warm up. Set the idle screw so that the engine is idling at a normal RPM. Take a small screwdriver and start turning one bleeder screw on one side of the carb inward until the idle either drops or rises.

How do you adjust H and L screws on a carburetor?

Set the idle speed screw (not L or H ) so it is just able to idle by itself. This screw will have a “stop” it rests against. Now turn the L screw out until in decreases in rpm and then back in(very slowly) until it is at peak rpm. Adjust the H screw once more as above and it should be a very serviceable 2 stroke.

How do you tell if a carburetor is rich or lean?

If the insulator near the plug tip is a nice light tan colour then it’s running approximately correct at that load/rpm. If they’re white then it’s running lean, if they’re a dark brown or worse colour then it’s running rich.

How do you tell if a bike is running lean or rich?

Typical symptoms of a rich mixture are:

  1. Poor fuel economy.
  2. Sluggish acceleration.
  3. Choke not needed from cold starts.
  4. Sooty or black spark plugs.
  5. Sooty or black muffler end pipes.
  6. Strong smell of gasoline when the machine is at idle.
  7. Uneven running (will often slow from regular idle rpms and then stop)

How do you set a carburetor mixture?

Carb Quick Guide

  1. Verify carburetor is set to stock settings:
  2. Start bike, bring to operating temperature.
  3. Set idle speed adjusting screw, clockwise to increase rpm, counter-clockwise to decrease rpm.
  4. Adjust idle mixture by turning idle mixture screw slowly clockwise until the engine runs poorly.

What are the two adjustment screws on a carburetor?

Find the adjustment screws on the front of the carburetor. There should be two screws on the front of the carburetor, which are used to adjust the air and fuel mixture. Often these look like flat-head screws and you can use a screwdriver to turn them, adjusting the amount of fuel and air mixing in the carb.

How do you adjust the carburetor mixture on a screw?

Locate the idle mixture screw and turn it clockwise until the needle lightly touches the seat. Then, turn the screw counterclockwise 1-1/2 turns. If your carburettor has a main jet adjustment screw at the base of the float bowl, turn the screw clockwise until you feel it just touch the seat inside the emulsion tube.

What are the symptoms of a lean fuel mixture?

Lean Mixture Symptoms –

  • It is difficult to apply the throttle quickly or the engine picks up speed when the throttle is rolled off.
  • The engine knocks or Pings or overheats.
  • The engine surges or hunts for a stable RPM while cruising at part throttle.
  • Engine acceleration is flat or slow to pick up.

How do you fix a lean fuel mixture?

What repairs can fix the P0171 code?

  1. Replacing the fuel pump.
  2. Replacing the fuel filter.
  3. Replacing the fuel pressure regulator.
  4. Replacing the powertrain control module.
  5. Replacing one or more injectors.
  6. Replacing one or more oxygen sensors.
  7. Replacing the mass air flow sensor.
  8. Repairing a vacuum leak.

Is it better to run rich or lean?

Running lean can give you more power but to lean will blow your engine. Running too rich can also hurt your motor. Think of it when you are mixing gas for your weed wacker. It is always safe to add a little more oil than not enough to the mixture.

Where is the idle screw on a motorcycle carburetor?

This screw could be on the left or right side of the bike. If you can’t find it, try checking on the other side. On some fuel-injected motorcycles, there is a knob sticking out the side of your bike near the engine compartment. You can just turn this knob clockwise or counterclockwise to adjust the idle speed.

Where is carburetor idle screw?

The idle mixture screw controls the air fuel mixture at idle speed, and often is located near the throttle plate.

Where is the mixture screw on a carb?

Most air fuel mixture screws are located on the side of the carburetor, but it depends on the specific engine.

How does a Honda carburetor adjust idle speed?

The carburetor automatically adjusts the mix across the entire throttle range. The carburetor adjustments include idle speed, idle circuit mixture, mid-range and high-speed circuit mixture. The idle circuit and idle speed is adjusted with a screw.

What should the idle mixture be on a Honda motorcycle?

Once the engine begins to misfire, back the idle mixture screw out just until the misfire stops. This is the optimal idle mixture setting. The midrange is checked by speeding the engine up to about 1/2 throttle.

How does the carburetor work on a Honda motorcycle?

Honda motorcycle carburetors deliver a precisely metered air/fuel mixture to the engines. The carburetor automatically adjusts the mix across the entire throttle range. The carburetor adjustments include idle speed, idle circuit mixture, mid-range and high-speed circuit mixture.

How does the carburetor adjust the throttle range?

The carburetor automatically adjusts the mix across the entire throttle range. The carburetor adjustments include idle speed, idle circuit mixture, mid-range and high-speed circuit mixture. The idle circuit and idle speed is adjusted with a screw. The mid-range and high-speed mixture is controlled by changing jet size in the carburetor bowl.

The carburetor automatically adjusts the mix across the entire throttle range. The carburetor adjustments include idle speed, idle circuit mixture, mid-range and high-speed circuit mixture. The idle circuit and idle speed is adjusted with a screw.

Once the engine begins to misfire, back the idle mixture screw out just until the misfire stops. This is the optimal idle mixture setting. The midrange is checked by speeding the engine up to about 1/2 throttle.

Honda motorcycle carburetors deliver a precisely metered air/fuel mixture to the engines. The carburetor automatically adjusts the mix across the entire throttle range. The carburetor adjustments include idle speed, idle circuit mixture, mid-range and high-speed circuit mixture.

The carburetor automatically adjusts the mix across the entire throttle range. The carburetor adjustments include idle speed, idle circuit mixture, mid-range and high-speed circuit mixture. The idle circuit and idle speed is adjusted with a screw. The mid-range and high-speed mixture is controlled by changing jet size in the carburetor bowl.

A motorcycle carburetor, being a key component in a motorcycle, must at times be adjusted to deliver the right mixture of fuel and air to the bike’s cylinder. If this mixture is not set correctly, it can affect the operational efficiency of the motorcycle. This, in turn, can increase the bike’s fuel consumption and can reduce its power. This setting adjustment is relatively simple and as a motorcycle owner, you should be able to adjust your own bike’s carburetor setting when you see a need.

Things you’ll need:

  • Clean cloth
  • Carburetor cleaner
  • Engine RPM gauge
  • Screwdriver

Step 1 – Remove Dirt, Debris, and Oil Deposits

Locate your bike’s carburetor and spray its outer surfaces with carburetor cleaner to dissolve any oil deposits that have built up over time and may be interfering with the efficient operation of your bike carburetor’s moving parts. Use a clean rag to wipe away these deposits, along with any dirt, dust, or debris that might be imbedded in them. If necessary, spray additional amounts of this cleaner, then wipe the surface with a clean part of your rag until all deposits, excess cleaner, oils, and grease have been removed.

Step 2 – Check Your Carburetor Fuel-Air Mixture

Start your bike and let it run. When the engine is warm, locate the fuel-air mixture screw. Usually you’ll find this adjustment screw on the carburetor barrel’s side, three or four inches down from the carburetor barrel’s top edge. Attach your RPM gauge to the carburetor by first detaching the bike’s vacuum hose. When the bike is running at a high idle, check the RPM gauge. If the RPM reads less than 1400, use a screwdriver and turn the mixture screw in a clockwise direction, keeping an eye on the RPM gauge. Stop turning the screw when the gauge shows an RPM of 1400.

Step 3 – Adjust Your Mixture Screw Setting

Your bike’s RPM rate when the bike’s engine is idling at a normal rate should be at the 1000 to 1100 RPM range. To get this RPM when your bike is at a normal idle and the RPM is higher than the normal range, turn the mixture screw in a counterclockwise rotation. At a point when you hear the engine begin cutting out, back the screw slightly until the engine is running smoothly again. The RPM range should now be between 1000 and 1100.

Step 4 – Final Mixture Screw Setting Check and Adjustment.

The final test for the bike’s correct fuel-air mixture should now be made. From the carburetor, remove the RPM gauge and attach the carburetor’s vacuum hose you removed earlier. Have your bike’s engine running at a normal idle. If you hear, or feel, any irregular firing of the bike’s cylinder, turn the screw slightly clockwise until the engine is running more smoothly. Then, re-attach the RPM gauge and check its reading. If it is showing an RPM in the lower range (near the 1000 RPM mark) adjust the mixture screw until the RPM is closer to the 1100 mark. Finally, remove the RPM gauge and reconnect the vacuum hose.

How to adjust idle on a motorcycle

Honda motorcycle carburetors deliver a precisely metered air/fuel mixture to the engines. The carburetor automatically adjusts the mix across the entire throttle range. The carburetor adjustments include idle speed, idle circuit mixture, mid-range and high-speed circuit mixture. The idle circuit and idle speed is adjusted with a screw. The mid-range and high-speed mixture is controlled by changing jet size in the carburetor bowl.

Idle Speed

Idle speed is adjusted with the idle speed screw on the side of the carburetor. Start the engine and bring it up to operating temperature. Refer to your specific model’s service manual for the appropriate idle speed range. Turn the screw clockwise to speed up or counterclockwise to slow down the engine while observing the tachometer until the target RPM range is achieved.

Idle Mixture

Adjust the idle mix with the engine running and at operating temp. Screw in the idle mixture screw until the bike develops a lean misfire, which will sound like the engine is sneezing back through the carburetor. Once the engine begins to misfire, back the idle mixture screw out just until the misfire stops. This is the optimal idle mixture setting.

Midrange

The midrange is checked by speeding the engine up to about 1/2 throttle. Listen to the engine and observe the exhaust gasses. A lean misfire indicates that the midrange jet is too small and must be increased at least one size. White exhaust gas indicates excessive free hydrocarbons (unburned fuel), and a too-large jet that must be decreased by at least one size.

High-Speed

Once the idle and midrange mixture are dialed in, the high-speed mix may be checked. The high-speed jet is checked while the bike is being driven. Speed the engine up to between 3/4 and full throttle with the bike in first gear. Listen for a lean misfire and observe the exhaust for excessive hydrocarbons. Adjust the high-speed jet size using the same parameters as with midrange–lean misfire, increase the jet one size; white exhaust, decrease the jet one size.

How to adjust idle on a motorcycle

Idle is useful for warming up your motorcycle engine. But after it’s reached the necessary temperature, leaving it at idle will make it stall. A common example is when waiting at a red light.

In this article I want to share the five most common reasons why a bike dies at idle, and the best ways to fix these issues without spending hundreds of dollars to hire a pro.

Table of Contents

Bike Dies at Idle: 5 Common Causes and Solutions

The Modern Fuel Injected Engine

The most common reason for your bike dying on idle is that the modern fuel injected engine runs on a very lean air/fuel ratio. This is the most likely cause but there are others to consider, especially if the problem is recent and hasn’t bothered you in the past.

Engine idle level set too low

Unfortunately, on newer motorcycles the idle level often can’t be changed. If it can be changed, it’s done by either using the adjustment knob if there is one, or adjusting the idle screws on the carburetor. In any case, this is a relatively easy two step process:

Step 1

Place your motorcycle in neutral and start the motor. Let the motor run for a few minutes to warm up. Once warm, take note of the motorcycle’s engine idle speed. Most motorcycles require an idle speed of 1,100 to 1,300 RPM (revolutions per minute) to operate properly at a standstill.

Step 2

Turn the idle screw slowly using a screwdriver, twisting the screw counter-clockwise to lower the motor’s RPM or clockwise to increase RPM. Stop adjusting the screw when the tachometer indicates the desired RPM range.

Twist the throttle open a few times and observe the tachometer needle as the RPMs fade. The needle should return to the desired idle speed. If not, readjust the idle and test it again.

Clogged charcoal canister in the fuel tank ventilation line

If the charcoal canister is clogged, it will prevent the gas fumes from entering or exiting the canister and cause all sorts of trouble. So it’s important to clean the canister when it happens. Here’s how to do it properly:

Step 1

Remove the charcoal canister by removing the top and bottom lines from the canister with a flat-head screwdriver. The canister has three lines on top and one line on the bottom. Use a ratchet and a socket if needed to remove the canister from the bracket.

Step 2

Place the charcoal canister on a flat surface. Start the air compressor up and let the air pressure build up to at least 50 psi. Shut the compressor off once the air pressure reaches the 50 mark.

Step 3

Insert the rubber tip of the air line nozzle fitting into the outer vent control valve pipe that is on top of the canister. This pipe is separate from the other two top pipes. The outer control pipe is the on the very end of the canister. The outer control pipe is also a little bit bigger than the other two pipes.

Step 4

Place the ends of your fingers over the openings of the other two pipes on top of the canister with one hand. Pull the air release trigger on the air line nozzle and allow the 50 psi of air to blow into the canister with the other hand. Continue blowing the air into the charcoal canister for about one to two minutes. Remove your fingers from the top pipes and place one of your fingers near the front opening of the pipe on the bottom of the canister.

Apply the air to the opening of the control valve pipe again and use your finger to determine if the air is coming out of the bottom of the pipe. This will ensure that the canister is clean and allowing air flow from the top of the canister to the bottom pipe of the canister. Reinstall the charcoal canister.

Faulty Lambda (Oxygen) Sensor

A Lambda sensor measures the amount of unburned oxygen in a motorcycle’s fuel exhaust.

If the oxygen level is too high or too low, the Lambda sensor sends a signal back to the bike’s computer that tells it to adjust the air/fuel mixture so that the bike can perform optimally and within emission control standards.

If the sensor is damaged, the bike engine can stall at idle and suffer from other related issues, such as poor mileage, catalytic converter failure, decreasing engine power at cruising speed etc.

You can test your motorcycle’s oxygen sensor and see if it’s working properly or should be replaced. Here’s a video explaining how to test it:

Fuel pressure too low

This problem is usually caused by a faulty fuel pump and may cause your engine to stall/die at idle. Common symptoms of a faulty fuel pump include:

  • A Whining Noise is Coming from the Fuel Tank
  • The Engine Stalls/Won’t Start
  • The Bike Surges

If you’re experiencing these problems, consider checking your fuel pump to see if it’s working correctly. Here’s a great video tutorial for doing exactly that:

Valve clearences too tight

There are many problems associated with tight valves. Mainly, the bike won’t idle cold, it will hang up at high idle when coming down from speed, and the fuel econ will be 25-40% lower.

Tight valves also lead to worn valve seats and deformed valves. This can lead to carbon deposit on the seat and reducing the fill and exhaust of gasses.

There is no reason to run a tight valve at all. The perfect balance is a smooth running engine with minimal valvetrain noise. Setting the valve loose has it’s own problems, so it’s best to take a centrist route on this one and have it neither too tight nor too loose.

Motorcycle mechanic, writer and Heineken lover. A bit like Hank Moody on a Suzuki.