Why is my Motorcycle idling so high?

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When it comes to motorcycle mechanical problems, it can be very frustrating. Just like any other vehicle, one problem could be caused by several different factors and sometimes it’s hard to know where to start looking.

High idle is a common problem on motorcycles. It can be annoying and dangerous for both you and your bike. It is important to diagnose the problem quickly.

So why does my motorcycle idle high? If the motorcycle is using too much fuel and air, it can cause it to idle up. This is often caused by an improper adjustment of the idle screw on your carburetor, a loose throttle handle screw or a bad carburetor throttle Spring.

Fixing motorcycle issues such as a high idle doesn’t always have to be a scary experience. Since 2006, I’ve been fixing and restoring motorcycles.

Why Motorcycles Are High

I can’t tell you how many times I’ve gone to start up a motorcycle only to be startled by the loud noise of a high rev that it starts with and continues to idle high. I have mostly owned older motorcycles, so the sound of the high idle isn’t exactly super pleasant.

You’re not alone if you’ve found yourself in this situation. This is a common problem on motorcycles, particularly older models with a carburetor. It’s a good idea to be come familiar with the signs and symptoms of a high idle and know how to tackle the problem because chances are you’ll likely run in to it again.

The motorcycle idles very high due to more fuel and air being sucked into it and combusting. Higher combustion results in faster piston strokes and crankshaft rotations. This increases exhaust flow and pushes air out, which makes it louder.

The most common reason why a motorcycle idles too fast is because the idle screw and air pressure are too high. This screw is used to prevent the throttle plate completely closing. This screw is located on the carburetor and can be turned and adjusted. It will raise or lower your throttle.

Each motorcycle’s carburetor is unique so you may find the idle screw in a different place. Refer to your owner’s manual to locate where it is and attempt to adjust it with a screw driver and see how your motorcycle reacts.

Sometimes you will find a stop button or a set screw at the right hand throttle. This is used to ensure that the throttle stays in place. Occasionally that screw will become out of place and won’t let your throttle release all the way so your motorcycle will constantly be throttled a little bit.

You can usually tell if this is the cause of the problem because the throttle isn’t doing a full turn. You should examine your throttle to see if it has a set screw that holds the throttle in place. If you find one, adjust it so that your throttle is free to move back and forth freely.

The spring on a carburetor pulls on the throttle when the throttle is turned. This spring helps to bring the throttle back into idle when it is released.

If that spring on the carburetor gets old or malfunctions, it won’t pull back the throttle to the idle position and also won’t close the butterfly valve inside the carburetor which leaves you in a high throttle position.

You can check if the problem is with the throttle cable by connecting it to the carburetor. If you notice it’s stretched too much or simply missing, replace it.

Sometimes, the throttle can be held in a high idle mode due to gunk or grime. The throttle cable can also be damaged by sticky or grime.

A CB650 I owned had these problems. I removed the throttle from the right-hand side. It was covered with gunk and had strange stickiness. I cleaned it and sprayed some oil on the cable lining of the throttle. There was still a lot of gunk.

Please note: Most fuel-injected motorcycles will briefly idle high after being started. Then it lowers. This is to ensure that the motorcycle heats up quickly. This is perfectly normal and not something to worry about.

A video series I created about motorcycle restoration from start to finish. It includes a 25-minute video detailing how to clean and rebuild carburetors. The series also covers other difficult-to-tackle parts such as electrical and body work. I give dozens of tips and tricks that you won’t find anywhere else online. Click here for more information if you’re interested in viewing multiple videos that will help fix up your bike or if you’re interested in completely building your dream motorcycle!

High Idle Riders Are At Risk

If you notice your motorcycle is idling high, it’s important to quickly address the issues and keep that from happening because there are a few risks involved if you continue riding like that.

Having a high idle means the motorcycle is getting power but isn’t using it because it’s stopping itself due to either the brakes, it’s in neutral, or it’s in a low gear. It is possible to feel the power building up while riding at high idle, but it can also manifest unexpectedly.

For example, if you come to a stop on the road either in traffic or at a stop sign, letting off the break a little bit can take you a lot further than you want to go because there’s so much power building up. It is possible to rear-end someone or run a stop signal.

There are also risks involved with your motorcycle if you’re riding with a high idle. It is possible for your motorcycle to shift extremely hard between gears, and you might even hear a loud clunking sound. This can later cause issues with your transmission and clutch because a hard shift like that isn’t good for the gears.

What RPM’s Your Motorcycle Should Be At

Having your motorcycle maintaining the right RPM’s is vital for it’s health. A motorcycle shouldn’t be at constant high RPM’s because that will wear out the engine a lot faster as well as rattle your ears and everyone else’s around you.

In combustion engines, the idle speed is usually measured in revolutions per minute of the crankshaft, or RPM’s. A good idle speed will generate the right amount of power to get the motorcycle going then increase to whatever you’d like it to be as you get going down the road.

A healthy RPM for most motorcycles should be between 700 RPM’s – 1,000 RPM’s. Some motorcycles are a little different from each other, so be sure to check your owner’s manual to make sure. You can often tell by its sound. Any idle higher than 1,500 RPM’s is considered high and should be adjusted.

How to Prevent High Idle

You may notice a high idle rate on your motorcycle. It can increase slowly or be so intense that you are completely surprised when it starts to get worse.

High idle can be hard to avoid unless you’re willing to inspect every bolt and nut on your motorcycle regularly. The causes of a high idle are usually pretty easy to fix, so it’s usually no big deal when you find yourself having this issue.

It is important to maintain the health and integrity of your throttle and throttle cables. Keep these items away from anything that might spill or cause them stick. Avoid leaving your motorcycle exposed to the elements or parking it under unattractive trees.

Similar Questions

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