How to Replace Belt on Bostitch Air Compressor? Step by Step Guide

A belt is an essential part of air compressors, it connects the motor and pump to start filling air in the tank. When compressors continue to run for a long time, their belt gets loose or sometimes it breaks. You have to change the belt to rerun the tool. No need to hire a mechanic; you can change the belt yourself. With our detailed guide, you can replace the belt, tight, loose or align it and save yourself the cost of a repairman. Let’s start!

5 Quick Steps to Replace the Belt

There are five steps included in changing the belt that is given below:

Removing Screws

Drain the air tank fully before proceeding. There are almost 3 screws on the front housing of the compressor. Remove them with the help of a screwdriver. Similarly, remove the 7 screws on the backside.

Put Out Pump & Motor

After removing the housing, you will see a pump and motor inside it. There are 3 types of wires there, green, yellow, & white also, unplug them. Now remove the 4 screws on the head of the pump to separate the motor area. Also, detach the piston by removing the bolt attached to the flywheel.

Installing New Timing Belt

Now separate the belt with the help of a screwdriver carefully. Your compressor maybe not function properly if the belt is loose. So, after removing the old belt you have to install the new one.

Be careful while installing the belt because it requires extra force to put on the pulley. Next, rotate the pulley 3 – 4 times to check if the belt fits properly and moving smoothly.

Reinstalling Parts

Start reinstalling the removed parts. First, tightly fit the piston with flywheel using the bolt. Now install the head of the pump and also fit it correctly. The next step is to reconnect the three wires, yellow, white, and green. After that, reinstall the housing and secure all the remaining screws.

Run the compressor 2-3 times a day so the belt can sit in the right place and run smoothly.

Aligning the Belt

It is one of the crucial factors in the performance of a compressor. When the belt of your device is not properly aligned, it continues to break, and that’s the reason why it keeps cracking the belts. So, you must align the belt before turning on the machine. Here are a few steps to check whether the belt is aligned or not:

  • Take a big ruler and hold it against the outside of the flywheel and other small pulley.  
  • Ensure it has the same level as belts, so we can easily get the measurement.
  • Take a measuring tape and calculate the distance from the belt end to the ruler end. Similarly, measure the distance from the middle of the flywheel and pulley. At last, calculate the distance of the small pulley belt connected to the motor. If the 3 points have the same value, your belt flywheel and pulley are aligned.

If the measurement you got from the 3 points is not matching, it means your belt is not aligned. How you can adjust the belt if it is misaligned. Let’s learn

  • First, we will adjust the motor pulley. There is a set screw in the pulley; you have to remove it.
  • Take a hammer or heavy tool and knock the motor shaft 2-3 times. This way, you can realign the motor pulley side.
  • On the flywheel side, the compressor has slots that can easily adjust by losing the bolts. Again measure the distance of the belt and rule, adjust the position of flywheel accordingly. Your belt will be aligned when you get the exact measurement on all 3 points.


Belt drive vs Direct drive – Which is better?

Belt driven air compressors need a belt system to run the machine. They are durable, quiet, and easily lubricated to provide a smooth, long-hours job. Whenever the belt gets broken, you need to change it, which automatically increases your maintenance costs. However, a direct-drive compressor does not require any belt to operate, continuous lubrication, & lowers your repair costs. I would say direct drive compressors are best.

Can a seized compressor destroy the belt?

While operating, when the air compressor suddenly gets stuck, it gives a severe shock to the belt that may result in breaking the belt. It does not cause any issue to the belt tensioner; when your belt breaks simply replace it.

Can I drive an air compressor without a belt?

If it is a belt-driven air compressor then it’s not possible. You must need a belt for making connections between the motor and pump. On the other hand, if you have a direct driven compressor, it doesn’t need any belt to run. Because the motor has a direct connection with the pump.

Where is the belt located in an air compressor?

Mostly, you can find the belt on the side of your air compressor one the two pulleys. If the compressor has housing, you can find the belt inside the housing.

How to measure what size of belt my air compressor needs?

Almost every compressor uses a v-shaped belt, and it’s a very simple method to measure the size of the belt. First, read the owner’s manual, or there is a code printed on the belt. You have to tell that code while purchasing a new belt. If your machine’s belt is lost and there is no way to recognize what belt size you need, call your brand’s customer support and tell them the model number. They will tell the belt code according to your device.

We also calculate manually the size of required belt here:

First, we calculate the diameter of 2 pulleys. Let’s suppose the diameter of big pulley is 10 inches and the small one is 5 inches.

Now measure the center distance of two pulleys; let’s suppose it is 26 inch.

The next step is to apply the formula to get the final number. The formula is L = 2C + 1.57 (D+d), L is the length, C is the center distance of two pulleys, 1.57 is the constant number, D is the diameter of big pulley, and d is the diameter of a small pulley. Put the values in the formula.

                                                L = 2(26) + 1.57 (10+5)

                                                L= 52 + 1.57 (15)

                                                L= 52 + 23.55

                                                L=  75.55 inch

So, you should need a 75.55-inch belt for your compressor.

How to open the belt guard on the air compressor?

It’s super easy to open the belt guard, take a screwdriver and remove all the screws. If your device is rusty and the screws are not opening, apply some oil and then try to lose them.

How tight or loose should air compressor belts be?

At first, you have to check the owner’s manual; they have provided the measurement of the tightness or looseness of the belt. On average, your belt should be loose ½ inch, and never make it loose because the belt may slip from the pulley.

Moreover, the belt must be tight from ¼ – ⅜ inch. Not more than this reading because the belt gets snapped if we make it much tight.

Why do some air compressors have two belts?

There is a timing belt in the compressor that runs pump with the help of the motor. Some air tools have two belts on the pulley; they speed up the pump’s functioning and reduce the pulley’s efforts to shift the load.

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