What to Do about Rattling Noises in My Generator

red generator in rain
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What You'll Need
Socket set with Ratchets
Long nose pliers
Vice grip pliers
Light plastic hammer
Long stem flat screwdriver with magnetized tip
Small tarp
Gas can
Siphon pump
What You'll Need
Socket set with Ratchets
Long nose pliers
Vice grip pliers
Light plastic hammer
Long stem flat screwdriver with magnetized tip
Small tarp
Gas can
Siphon pump

A generator is an extremely useful piece of equipment to own, especially when considering the intensity of storms occurring at an increased pace for the past few years and in locations sometimes that have never witnessed them as much in the past.

Power outages have become much more frequent these days, but worst, they seem to affect greater areas for much longer periods of time, often impacting hundreds of thousands and even millions of households for days and even weeks at a time.

A power outage occurring in the winter can quickly become extremely worrisome as the temperature in your home gradually drops toward the freezing point while you’re deprived of your phone, TV, and radio to find out what’s happening around you.

And that’s not counting on the fridge and freezer no longer running, or the possibility of warming or cooking any food throughout the blackout.

Owning a Generator

Having a generator handy in the garage, you may not feel as worried and feel more confident than the next guy, should an outage occur. But have you checked your generator lately, replaced the spark plug, checked the air filter, and changed the oil?

When your generator is running, does it produce weird or unfamiliar noises? The equipment is designed to run smoothly, and the noise coming from it should always remain even and regular.

When the motor starts to miss or backfire, or when you start hearing a rattling noise coming from the generator end of the equipment that never used to be there, you know then and there that something is not right.

The thing is, though, that you don’t want to find out that your generator is not at its peak performance the day the power goes out. For that reason, you should run a regular inspection of your generator after every outage. Listen, smell, and look for anything out of the ordinary and investigate further.

Troubleshooting a Generator Making a Rattling Noise

If the generator produces a rattling noise originating from the engine, the chances are most likely that it is related to a metal protective cover that has gotten loose from the engine covering the exhaust manifold or some other part around the motor.

While the engine is running, you should be able to spot the loose cover quite easily as it shakes around, but if you can’t see it, stop the engine and let it cool down. Once it is cool enough so that it’s cool or just warm to the touch, check every cover one by one to find the loose one, and tighten it back up.

A different problem was found on a Briggs & Stratton 2100 generator model 030664. This particular generator is rated at 8000 Watts running with 10,000 starting Watts.

For three past outages, a rattling noise could be heard coming from the generator end of the unit, not very loud at first but perceptible. That would have been the previous winter. But there was no flicking of the lights and no drop in voltage, so it was left like that.

The noise wasn’t very loud, and it was blamed on a metal cover or some other part that got loose but never investigated any further.

The rattling kept getting louder, however, and during the last outage, which lasted over 12 hours, it became loud enough to be heard from inside the house. With a promise finally to look into it as soon as the power outage was fixed, the generator did its duty for the whole time the power was out.

Once the power came back on, it was left running to watch the end of a movie on TV, with maybe 15 minutes left to watch. But that was when the lights started to flicker off, then back on repeatedly.

The generator was immediately turned off, but what happened was that the armature’s bearing at the bearing retaining cap at the rear of the generator went bad and started coming apart (as seen in Figure 1 below).

generator engine

Figure 1

This left an extremely heavy armature spinning loosely at 3600 RPM at one end, causing it to vibrate, thus causing the rattling noise. The excessive vibrations applied against the bearing continued to literally destroy it, increasing the vibrations as it went.

The Costs of Neglect

As this went on, something else was happening elsewhere on the armature, or more precisely, at the commutator where the brushes were making contact.

The vibrations coming from the commutator were transmitted directly to the brushes, also causing them to vibrate, moving back and forth at high speed and along the wires connecting them to the contactors on the brush holder.

And this is where eventually, both of the wires from the brushes broke off from their respective contactor, causing the power to cut out (Figure 2).

generator engine with star icons

Figure 2

The two yellow stars in Figure 2 show where both of the brush’s wires broke off from their contactors. This clearly illustrates how neglecting to check on a problem, no matter how small, can increase the cost of your repairs.

This particular case also could have cost a new armature as the affected one showed signs of heating up on a few windings, but just short of compromising the insulation of a field winding.

1. Get the Generator Ready


If your generator is set up as a stationary unit with a permanent setup feeding directly into a sub-panel in your basement, you’ll have to unplug all the cables leading to it, including the ground wire, which you should have in such a case.

In most situations, the repairs will usually be done with the heavy piece of equipment sitting on the floor instead of on a workbench, so you should clean an area of the floor where you can access your generator from any side and where it can be left untouched if the repairs should require a few days to complete.


Before moving the unit to that particular spot, you should spread out a small trap or a large cardboard to cover the area and prevent any leaks to soak into the floor or ground and also to catch any parts falling on the floor.

Get yourself some knee pads, a large foam pad, or an old blanket to put on the floor to protect your knees, especially in the winter months.

You should also get yourself ready with a large enough pan to collect all the nuts, bolts, washers, and other parts that will be removed from the generator. A bright work light or flashlight is also a must to inspect the inside of the assembly.

As there is always a possibility that some small nut or washer falls inside, a long-stem magnetized screwdriver can quickly become a great asset for fishing the parts out from inside the generator casing.


You might also find that you’ll often get a better view of the inside or get a better chance to reach some of the bolts if the unit is tilted up.

This is where it’s important for you to drain the generator from all of its gas, as it would just simply leak out on the floor or on the ground while in the tilted position.

In most cases, it would be fair to assume that there is some gas left in the fuel tank. And with the case stated here, where the generator was stopped suddenly upon a malfunction, it’s safe to assume that there was still gas left.

You can safely extract the gas from the tank with a siphon pump and easily transfer it to a gas can.

So no matter what, remove the gas cover, check inside the tank for gas, and if there is any, insert the inline hose of your siphon pump inside the tank and, submerge the end in the liquid, then drain the tank out.

2. Open Up the Generator


There are usually two screws holding the outside end cover to the bearing retaining cap, which is the large aluminum casting at the end of the generator casing. Remove both screws and take the cover off.

This will expose the back end of the casing assembly, the armature bearing, the voltage regulator, the terminal block, and most of the wiring (Figure 3).

You’ll find all of the wirings tightly packed in place to fit perfectly, so taking pictures at several angles of the full layout before disturbing anything could prove extremely beneficial in the end.

generator engine with named parts

Figure 3


It is very important at this point that you get your cell phone ready and take plenty of pictures to illustrate every detail of the generator before actually proceeding to the next step.

It is ultimately important that you take many clear pictures of the wiring, showing, whenever possible, the identification sleeve and every terminal with all the wires still hooked up to each one.

The removal of small parts, such as the wire clamps with the placement of the wires, brush holder, and terminal blocks should also be carefully documented.


With the outside cover removed, take a good look at the armature bearing.

This should be a sealed bearing, so if there are any ball bearings showing, and if there is debris around the bearing area, you’ll know that the seals are gone, and the bearing is badly damaged and needs to be replaced.

generator engine

Figure 4

You can also see a larger bolt right on top of the bearing.

Get the proper-sized socket and remove that bolt from the assembly with your ratchet, watching to avoid damaging the rotor (or any part of the armature) while holding it steady so that it doesn’t turn as you remove the bolt.

3. Remove Components From the Bearing Retaining Cap

Before the bearing retaining cap can be removed from the generator casing, several parts have to be removed to free the bearing retaining cap casting from the Stator.

All the wiring from the stator is hooked up either to the terminal block or to the voltage regulator somehow and needs to be disconnected.

generator engine with wires

Figure 5


As seen in Figure 5, a large harness with several wires leads directly to the terminal block, with four of its wires each connected to a different terminal on the terminal block.

Before taking anything apart, take several clear pictures showing the terminals, how, and where each wire is attached. One by one, you can start removing the nuts from the terminals.

Start with the easiest ones to remove, take out the nut and washers, and remove the wire, then immediately return the washers and nut to the terminal screw in the same order they came out.

This is where the magnetized screwdriver previously mentioned in section 1.2 will come in handy, as some of the washers or nuts might slip and land into a hard-to-reach place inside the stator.

A skinny flat screwdriver with a magnetized tip can then be used as a “reacher,” which is conveniently inserted inside the stator next to the part where it can be picked up by the magnetic flux and retrieved.


A 5th green and yellow ground wire and another ground wire with one end connected to the end terminal on the terminal block should now be disconnected from the bearing retaining cap casting by removing the screw identified by a yellow circle in Figure 6.

With these ground wires disconnected, the complete harness is now disconnected from the generator.

The terminal block can be unscrewed from the bearing retaining cap and pulled out while still held by the wires from the stator inside the generator.

generator wires with diagram circles

Figure 6


The voltage regulator is then unplugged from the generator—through the white connector circled in red in Figure 7. You’ll probably have to unscrew and remove the connector from the casting first before pulling it apart to disconnect it.

Once you unscrew the voltage regulator from the bearing retaining cap, you’ll see that it is only left hanging by a red wire and a white wire connected to the brush holder. Insert Figure 7 Here:

generator engine with red diagram circle

Figure 7


In order to remove the brush holder, you’ll need first to unplug both of those wires coming from the voltage regulator from their terminals on the brush holder (Figure 8).

With the harness from the voltage regulator already unplugged in step 3.3, you can finally remove the screw shown in the bottom leg of the holder and extract both parts from the bearing retaining cap. Insert Figure 8 Here:

generator wires with diagram circle

Figure 8


The last wire left to remove from the bearing retaining cap is the black ground wire coming from the control panel shown in Figure 9. You can remove it by unscrewing the screw holding it to the aluminum casting. Insert Figure 9 Here:

hand working with generator wiring

Figure 9

4. Remove the Rotor

There are two sets of very long bolts holding the bearing retaining cap in place. Figure 10 shows 4 bolts with yellow arrows that are used to secure the bearing retaining cap to the generator engine.

Two of the arrows in yellow only show the location of the bolts as they’re hidden behind the casing. 2 black bolts shown with red arrows are used to join and secure the bearing retaining cap to the stator.

It should be noted that the two black bolts are secured with nuts of the same size as the bolt heads at the other end of the stator. A small wrench will be required to hold the nuts while removing those two bolts. Insert Figure 10 Here:

generator with parts identified

Figure 10


Remove the set of 4 bolts holding the generator to the engine. You can now unfold the 2 tabs seen on the stator cover in Figure 10 (on the left side) and remove the cover which in this case is only a thin sheet of metal wrapped around it for added protection.


This next step is to loosen the stator from the engine casing and the rotor from the engine shaft. First, remove the large bolt that goes through the full length of the armature at the center of its shaft. Check for threads inside the hole that the bolt was in.


If there are threads, you’ll need to get a bolt about 2 inches long with threads matching those in the shaft. You’ll also need a length of rod that will fit inside the shaft but is larger than the bolt you just removed.

Insert the rod inside the hole until it hits the other end, then make a mark on it where it reaches the top of the shaft. The rod should be cut about 1/2 inch short of the mark.


If the shaft is not threaded, you’ll need to get a threading tap to fit and cut about 1 inch of threads down the hole. You’ll also need a 2-inch bolt (approximately) also with the same thread. You can then get a rod as described in the previous procedure and follow the steps described thereon.


Insert the rod inside the shaft, followed by the bolt, and start screwing it in the shaft until both pieces tighten up inside. You can secure the armature to keep it from turning, and with the proper size socket, screw in the bolt inside the shaft.

You’ll then notice the armature-stator assembly starting to slide out as it breaks its bond with the engine.

You will not be able to pull it out through the stator, though, as the armature cooling fan next to the engine is larger than the inside diameter of the stator housing.


Once the armature and the stator come loose from the engine, it’s time to separate the carrier-bearing cover from the stator.

This can be done simply by removing the two black bolts from the carrier-bearing while holding the nut at the engine end of the stator.

With those two bolts removed, you can now return the large bolt in place through the shaft and screw it in without tightening it, just to hold the armature in place and avoid damaging it during extraction.


The bearing retaining cap should be removed carefully while passing the terminal block through the opening—with its wires coming from the stator still connected.

If the bearing housing is jammed from the breakdown, you should proceed carefully to remove it, as you're also working to salvage the bearing retaining cap's aluminum casting.


With nothing else in the way, the stator can now be pulled out completely, showing the armature still inside.

You can finally remove the armature with the inside ring of the damaged bearing probably still stuck to its shaft.

In this particular case, it was decided—in order to avoid damages to the commutator or the windings—that the armature would be taken to a professional shop that removed the old bearing and replaced it for $45, including bearing and labor.

5. Re-Assemble the Generator

Putting the generator back together is going to be a different process consisting of re-assembling all the components together, the joining that assembly to the engine.


Assemble the bearing retaining cap to the stator, careful to line them up in their right position so the wiring to the terminal block can be passed through the opening in its right spot.

Secure tightly with the two black bolts through the full length of the stator.


Insert the armature in its position in the engine shaft and insert the long bolt inside the shaft and screw it in but without tightening it yet.


Take the stator and bearing retaining cap assembly and bring it over the rotor while lining up the stator with the engine bracket and the rotor bearing into its housing on the bearing cap.

Use a small plastic hammer lightly to tap the cap onto the bearing to where the stator rests on the engine bracket.


Take the four long bolts and screw them in each of their respective spots onto the engine bracket. Tap gently around the bearing housing to make certain that unduly pressure is not applied against the aluminum casting until everything is secured and in place.


Secure the bearing retaining cap back to the vibration mounts.


Install the brush assembly, the voltage regulator, and the terminal block making sure every wire is connected to its rightful terminal or connector. Secure all the wire brackets back in their position. Make sure that every ground wire is reconnected to the right posts and terminals.

With all this done, you’re now ready to put gas into the tank and start up the engine. Your generator should be ready to go.

To make sure that all the wiring was connected properly, you can use a multi-meter and take measurements across the two hot sides (220 V), the neutral, and each of the hot sides in turn (110 V each), and also check the readings to grounds at different places on the chassis.

If you would like to explore further related articles concerning generators, you can find much more concerning “How to Ground a Portable Generator”, How to Install a Generator Voltage Regulator,” and “7 Must Know Tips For Using Your Generator Safely.”