7 Engine Problems With Harley Davidson 96 Cubic Inch & (M8)

The Harley Davidson 96 cubic inch is a twin-cam engine released as part of a series from 1998 to 2017. It is the successor to the Twin Cam 88 model that ran from 1998 to 2007.

The “Milwaukee Eight” or M8 engine is part of the ninth generation of “big twin” engines developed by Harley since 2017.

This Article Explains: “The 7 Most-Common Problems with Harley Davidson 96 Cubic Inch & Harley Davidson M8 Engines”…

Here Are The 7 Most-Common Engine Problems In Short:

Despite being regarded as one of the most reliable Harley engines ever, there have been some notable Harley Davidson 96 Cubic Inch over the years, including issues with the cam chain tensioner, the oil pump, and the bearings.

As for the M8 engine, there was first a major issue with the oil pump used, some issues with cold starting below 50 degrees Fahrenheit, as well as the transmission vent and the piston oilers.

Most-Common Problems With Harley Davidson 96 Cubic Inch

While the Harley Davidson 96 cubic inch twin-cam engine was largely seen as one of the best they’ve made, 3 particular issues that it suffered were connected to the cam chain tensioner, the oil pump, and issues with the bearings.

Let’s look at each in turn.

Cam Chain Tensioner

Some argue that the choice of plastic shoes riding on the cam chains was a design flaw in the twin-cam 96, but also a design flaw born out of a desire to improve the overall experience.

It is thought that the use of plastic shoes would help to reduce excess noise.

The problem is that if the bike owner doesn’t realize in time that there is an issue with the plastic rubbing away, then sooner or later it will be metal to metal contact and a lot of damage can be done.

Oil Pump

The Harley 96 cubic inch also had issues with the oil pump getting jammed. This would be worse when the first issue with the cam chain tensioner was going on.

If the worn plastic bits get into the oil pump, then they can prevent oil from flowing into the engine.


If the oil pump is jammed, then it leads ultimately to the third common problem, which is that oil won’t go through to the bearings to lubricate them properly.

This subsequently causes damage to the rods, pistons, and other engine components.

Most Possible Solutions?

To stop these three common problems, the best solution to all three is to trace them to the source, which is the issue with the plastic feet on the cam chain tensioner.

If you ensure that the plastic components are not allowed to wear down too quickly, then the other problems won’t follow.

It requires constant vigilance on the cam chain tensioner so that issues don’t spill over into other components.

Another key point is to keep any Harley-Davidson motorcycle carrying the twin-cam 96 engine well oiled and lubricated.

Most-Common Engine Problems With Harley Davidson M8?

Interestingly, the Milwaukee 8 (M8) engine was generally very well received with very few complaints from Harley owners, even though there were some definite teething problems upon its initial release.

1. Oil Pump

From the moment that the M8 engine was launched, it was noticed that the oil pump was either a poor choice or just the wrong component, with many reporting problems.

The problem persisted on models through 2017-2019.

What was happening was the oil was sumping, which means that instead of returning to the oil tank where it should be going, it builds up in the crankcase and the cam gear case, which causes friction and power loss in other parts of the bike that are quickly becoming starved of oil.

2. Cold Starting

Many users of the M8 engine reported experiencing difficulties in cold starting at temperatures under 50 degrees Fahrenheit.

In cold temperatures, the engine was just refusing to start up.

One of the reasons for this is the increase in additional electronics that are present on bikes from that time and beyond. The electronics drain the battery and make the start harder and harder in the cold weather.

The other main reason is to do with the engine oil becoming too viscous in the cold.

If your battery is charged and it won’t start, then the problem is the oil.

3. Transmission Vent

There were some reported issues with transmission fluid levels being wrong on the bike because too much was being transferred across into the transmission housing reserve when it wasn’t necessary, causing levels to become imbalanced.

4. Piston Oiler

One other problem that was common in the M8 was engine revs getting too high, which in turn would send oil pressure too high and cause the piston oilers to come loose.

Most Possible Solutions?

The oil pump issue took some time to fix, but with a combination of recalls, new vents, and replacement oil pumps, the issue has now largely been fixed on newer models.

If you are buying a model from 2017-2019, you should inquire about the oil pump and if it’s the factory pump or a replacement.

Cold starting can be fixed by making a switch to a less viscous oil in the winter months.

First one should check the battery levels to make sure there is power. If the battery is ok, then the problem is most likely the oil.

The transmission fluid issue was fixed in the same way as the oil pumping issue, by replacing transmission vents and through careful repairs.

There was no quick fix. Once again, if buying a model with an M8 engine from 2017-2019, inquire about those repairs.

Finally, for the piston oilers, replacing them without splitting the cases is very challenging.

Most have to do a complete overhaul to make it work, but if you can’t afford that, you can look for a repair specialist who knows about replacing them without splitting the cases.

What Are The Symptoms And Causes Of A Failing Harley Engine?

As with most motorcycle engines, the signs of failure are fairly uniform.

If you detect any of the following symptoms, it signals that your Harley engine might be in need of professional attention.

1. Difficulty starting

Cold starting or not, when you are struggling to get the bike started, it means there is something wrong in the engine.

It could be something simple like needing thinner oil in the cold, or it could be something more mechanical.

2. Engine misfires

If you are getting misfires – hesitation in acceleration – then this is another big sign of imminent engine failure.

In a car, you’d be getting a flashing red “Check Engine” light which usually means “stop right now and call a mechanic.”

3. White or blue exhaust

If you see white or blue exhaust coming from the tailpipe, then that’s another very bad sign that the engine is experiencing extreme difficulty.

The color in the smoke is typically caused by broken valve seals that are allowing oil to get into the engine’s combustion chamber.

Can The Carburetor Be Related To These Problems?

On just about every motorcycle, including Harley-Davidson bikes, where there is a carburetor there is a chance for many engine problems to occur.

When it comes to the carburetor, the key is making sure that the unit is not clogged up. This means regular cleaning and maintenance on the carburetor unit and its jets.

7 Easy Things To Check If the Engine Is Not Starting?

  • Check the Battery
  • Assuming Battery is Good, Check If There’s Gas in the Tank!
  • Did you Engage the Clutch?
  • Is The Motorcycle in Gear?
  • Are There Any Loose Wires?
  • Is Your Kill Switch Off?
  • Check the Fuel Injection System and Spark Plugs!

What Are The Pros And Cons Of Harley Davidson 96 Cubic Inch


  • New cam drive design brought Harley bikes into line with EPA noise restrictions
  • Transmission casing was attached directly to the engine, which was a better construction and design choice compared to the previous displaced design in the Evo engine
  • Combustion chamber changed from “D” shape to “Bathtub” shape, which creates a more efficient combustion environment
  • Cams made with one per cylinder and each carrying 2 lobes, which meant that the rods enjoyed better alignment with the rocker arms.


  • Quieting measure led to excessive wear and tear on chain tensioner, which forces many to seek aftermarket solutions anyway
  • Still not liquid-cooled: even with improvements to the cooling fin areas and the insertion of a new oil jet, it was still not as efficient as a liquid-cooled engine

What Are The Pros And Cons Of Harley Davidson M8


  • Two extra valves added for each cylinder head helped the M8 to offer better torque than its predecessor
  • The M8 boasted a much greater intake flow capacity; about 60 percent greater than that of the previous Twin Cam models
  • Same weight as predecessors, but allowed for greater acceleration thanks to better torque ratings
  • More fuel efficient than previous models, and lower heat output which made riding more comfortable for Harley owners


  • Early models were dogged by oil sumping problems caused by problematic oil filters. While many have since been repaired, it makes buying earlier models riskier.
  • It’s only available on Touring and Trike models. It’s unfortunate that the engine, despite being a big improvement on predecessors, is only available on a limited number of models.

What Do Other Harley Owners Say?

Harley owners are an interesting group because they always defy industry responses to Harley-Davidson when it comes to mechanical reliability and performance.

Harley owners are far more likely to be positive about their bikes even if there are issues because they are fiercely loyal to the brand.

Having said that, there are some owners who despite their brand loyalty couldn’t help but point to one or two of these problems.

In particular, oil pump and oil sumping issues were unavoidable in the M8 engine between 2017 and 2019.

For the 96 cubic inch engine, the use of plastic teeth on the cam tensioner caused some ire, but Harley owners tend to remain positive and find solutions – even aftermarket solutions – to work around these problems.

Where Were These Models Made?

Both the 96 cubic inch and the M8 engines – along with any and all V-Twin class engines – are made in Harley-Davidson’s home base of Milwaukee, Wisconsin.

This was the birthplace of Harley-Davidson and is still the center of its engine development work.

The company has facilities in Kansas City, Missouri, and York, Pennsylvania, as well as a small factory in Tomahawk, Wisconsin where fiberglass and plastic components are made for some of the touring bikes.

What Is The Resale Price Of “96 Cubic Inch” & “M8”

For a used 96 cubic inch engine, you can expect to pay anywhere from $2500 to $3500 depending on the condition and year of manufacture for a 96 cubic inch engine.

New M8 engine units are selling for between $6100 and $7000, so for pre-owned units, prices can range from $3000-5500 depending on the condition of the engine.

Interestingly, the price of both these engines is more influenced by how modified they are and not how original. Where originality is usually an asset, in this case, it’s not.

The original versions had design and mechanical issues that were later fixed and modified by users.

Therefore, those that are modified from the factory specification are likely worth more.