RPMs Stay High After Revving? – Top 14 Reasons & Fixes!


Is your bike struggling with high RPMs after revving? Thousands of riders have faced this problem at one point or another.

Usually it’s a problem stemming from throttle cables that are either not lubricated properly or maladjusted. But transmission fluid, worn out clutch and other parts can also play a huge role.

Here’s a list of the 14 most common reasons for high RPMs after revving and fixes that will help you eliminate this problem for good.

Throttle Cables Are Not Lubricated

Throttle cables(amazon aff. link) are a common cause of excessive or unusually high RPM especially when they are not properly lubricated, dirty frayed or improperly adjusted. These parts should be checked and adjusted or lubricated regularly to eliminate the problem.

Sticking Ignition Advancer

If this is the case, examine the ignition advancer, carefully clean it, lubricate and just ensure it operates smoothly.

Problems with Transmission Fluid

Transmission fluid carries power from the engine through to the transmission. The fluid is important as it also helps in lubricating various parts of the transmission system. Gearbox band slippage or even torque converter issues may cause the transmission fluid to leak. When this happens, the engine RPM goes high after revving. On the other hand, gear shifts may begin to delay or even become more erratic.

Some of the reasons that may cause transmission problems leading to higher RPM include:

1. Transmission Fails to Stay in Gear or Engage

When you put your motorcycle or other vehicle on gear but it fails to move, the most likely culprit is low transmission fluid which may be as a result of leaks. However, this could also be a problem with the valve body of the automatic transmission. If you are using a modern vehicle with computerized transmission system, you may need to troubleshoot the transmission codes.

2. Missing Gears or Delayed Shifts

Transmissions may take longer to go into gear due to low transmission fluid that may have been caused by a leak, contamination or sometimes a result of water intrusion caused by flooding conditions. Although this may not be a serious cause of alarm, it may contribute to overheating effects which may as a result cause damage to the internal transmission parts. As a result, your engine may experience increased RPMS after revving. The other possible problem could be a computer related error which stops the gear from moving into a higher one resulting in unusually high RPMS.

3. Transmission Slipping

Low transmission fluid may be the cause of problem or sometimes internal tear and wear affecting some of the transmission parts. Worn clutches for instance will cause your engine to rev abnormally high.

4. Leaking Transmission Fluid

If you monitor closely and observe a red fluid under your vehicle, you should be worried of a possible transmission fluid leak. This is particularly dangerous to the vehicle if the fluid leaks on a hot surface. It is recommended that the fluid level be regularly monitored using the dipstick in order to maintain a proper fluid condition and level.

5. Burning Smell

Many users report that when they had this experience, a burning smell was always in the air. It is true a burning smell, cause by fluid leak or as a result of low fluid results into a burning clutch smell. However, I this is identified in good time, the transmission may be rescued from the possible damage.

6. Humming Noise

A roaring or humming noise from within the transmission is many times a symptom of gears damage, bad bearing or other internal damages.

7. Gears Grinding While Shifting

If you notice gears grinding any time you attempt to shift gears, it may be a sign that the clutch is not releasing or the shift synchronizer rings are broken or worn out. Also, the transmission oil may be low, dirty or the engine is running on the wrong fluid. This problem is particularly common with manual transmissions.

Worn Out Clutch

In manual vehicles, clutch is known to interact with the transmission system making it easier to change gears. When the clutch is wornout or slips during operation, the engine revs higher. This happens as the transmission will be struggling to work correctly. A slipping clutch also causes a vehicle engine to lose power, and rev highly while struggling to keep up the speed.

Defective Speed Sensor

Automatic vehicles characteristic of the modern vehicle industry use speed sensors. These sensors help the vehicles to determine when it is necessary to shift the gears up or down. If the speed sensors become faulty, they may fail to shift gears as required. This may cause the vehicle RPM to increase as the engine needs to work extra hard in order to perform the required task.

Dirty Fuel Injector

As opposed to the traditional carburetors, fuel injectors are the modern way through which vehicles move fuel from the fuel tanks through to the internal combustion chamber. They are modern and more efficient than the old school carburetors. However, they are more susceptible to dirt which clogs them after a while.

In order to counter this problem, most riders or drivers use fuel injector cleaners(amazon) or just some gas additives to keep the injectors on check over time. If you don’t use any of these, there are higher chances your fuel injector will get very dirty at some point. This causes poor combustion and may contribute to a very high RPM.

Defective Idle Control

High RPM especially when idling can be closely associated with a faulty idle control valve. The idle control valve for every vehicle helps the vehicle to maintain a constant RPM on every idling. The valve has a fuse which may make the valve dysfunctional especially when blown.

Bad Spark Plug or Ignition Wires

Damaged or worn out spark plugs are likely cause of rough idling. As the gadget that sends electrical current into the combustion chamber in order for the fuel-air mixture to be ignited, any problem with the plug affects ignition and RPMS.

Note that if the plugs are not in good condition, they won’t produce enough electric current for the ignition. This results into inconsistent combustion which eventually results into a rough idling. Consequently, the RPM may considerably go high.

On the other hand, bad or damaged spark plug wires or ignition coils leads to a similar engine problem as bad spark plug.

Incorrect Cam Timing

Incorrect cam timing may likely occur during a replacement or adjustment during repair. If these valves are poorly times, which means both the intake and exhaust valves are not open as appropriate, compression may be reduced and gas may be caused to travel to unintended locations. This way, the loose belts contribute to rough engine idles and even high RPM.

Clogged Air Filter

Your vehicle or motorcycle engine requires clean air from the outside in order to get a sufficient fuel-air mixture in the internal combustion chamber for a more efficient combustion. Every vehicle therefore has a key component which is the air filter. This gadget prevents debris from entering the combustion chamber.

A dirty or clogged air filter means that there is no sufficient air entering the combustion chamber. This results into an incomplete combustion and will always cause the engine to idle roughly. Because the engine struggles to burn the gasoline, the RPM speed may considerably get higher.

Vacuum Leak

A vehicle has a number of hoses that contribute to air and fuel delivery into the engine’s internal combustion chamber. The vacuum hose may have been worn out, damaged or just loose and has a leak. Any problem with the vacuum hose causes high and rough vehicle engine idling.

If this happens, a large volume of air mixes with fuel and may easily cause a misfire. The result is a vehicle that has a rough idle with an abnormally higher RPM.

Issues with The Carburetor

Carburetors are more traditional to the modern fuel injectors. However, if your vehicle still uses a carburetor, it should be inspected for being a culprit in an increased engine RPM or generally a rough engine. A good indicator of carburetor problems is black smoke coming out of your exhaust.

Bad Idle Air Control Valve (IAC or IACV)

This vehicle engine component helps to adjust the volume of air going past the throttle when the plate is closed. This system regulates engine idle speed and ensures a regular idle even with the air conditioning or headlights on.

Some of the symptoms of a bad idle air control valve one should monitor include:

  • Randomly fluctuating idle speed
  • Rougher engine idling
  • Frequent engine stalls
  • Check engine light comes on
  • Backfires

Incorrect Ignition Timing

This happens when the piston comes up and the spark plug is fired just before the piston reaches the top dead center. When this occurs, there is enough time for the fuel-air mixture to start burning and reach maximum efficiency. However, if the timing is advanced too far, the spark lights the fuel before the mixture is fully compresses resulting in an explosion.

Consequently, the expanding fuel catches up with the piston midway. This is because the piston is under pressure from the top and bottom. However, while in this situation, the fuel detonates and may burn holes on top of the piston, valves may burn in the process or the connecting rods may fracture. As this occurs, the detonation which comes as a result of an excessively advanced ignition comes back under extremely high RPM.

Luka Barron

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

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