The Milwaukee-Eight (M8) engine has become a modern classic, quickly gaining popularity among Australian riders. The M8 is the successor to the Harley Davidson Twin Cam engine and was first introduced in 2016.
The M8 engine is very different from the other engine designs used in Harley-Davidson motorcycles. For instance, it returns to a single-camshaft configuration and has internal counterbalancers.
If you want a riding experience that is a modern take on a classic engine, any Harley Davidson running an M8 engine is perfect. With that being said, due to the M8’s unique and fresh design, maintenance is slightly different compared to its predecessors.
This guide will cover everything you need to know about the Milwaukee 8 engine. This includes how frequently you should go in for servicing, the best oil for the Milwaukee 8 engine, and signs that there might be an issue.
Maintenance Needed For Harley Davidson Milwaukee 8 Engine
The maintenance and servicing schedule for Harley Davidson bikes with an M8 engine is slightly different from those with the predecessor, the Twin Cam engine. Routine maintenance is critical for longevity and ensuring your bike rides smoothly.
Below, we’ve outlined the general maintenance required for M8 engines. Keep in mind that specific maintenance needed will differ depending on the model and production year.
- If you have a new Harley Davidson motorcycle, it’s important to go to your “break-in” first service at about 1,600 kilometres. At the first service, they will change the engine oil and filter, check the transmission oil, and inspect the motorcycle’s components.
- After the first service, the bike should be serviced every 8,000 kilometres or so or annually, depending on whichever comes first. This service is for changing the oil and filter and inspecting the bike.
- If you’re wondering about the Harley Davidson M8 oil capacity, it typically takes 4.5 quarts of oil when changing the filter. Harley Davidson recommends 20W-50 synthetic oil for most riding conditions.
- The transmission fluid should be changed every 32,000 kilometres. It’s important to use Harley-Davidson fluid and check the owner’s manual for specific instructions.
- The spark plugs should be replaced every 40,000 kilometres under normal circumstances. It is important to inspect them every 8,000 kilometres.
- For motorcycles running an M8 engine, the coolant should be replaced every 48,000 kilometres. You’ll need to drain the coolant from the radiator and engine block and replace it with Harley-Davidson-approved coolant.
- Brake fluid should be flushed and replaced every two years. Failure to replace the brake fluid is a safety hazard.
- The Milwaukee 8 engine features hydraulic lifters, so unlike other engines, there is no need for regular valve adjustments. The only time it needs to be brought in is if there are any abnormal sounds.
Many M8 Harley Davidson motorcycles also come with built-in diagnostic systems. These systems can make it easier to find, diagnose, and fix any issues with the engine and electronics.
We recommend always going to a technician who specialises in Harley-Davidson motorcycles when going in for a routine service. If you plan to perform maintenance yourself, make sure to follow the owner’s manual and use the recommended Harley-Davidson fluids.
Signs Your Milwaukee 8 Engine Needs Servicing
Motorcycle engines, including the Harley Davidson M8, don’t just start causing problems out of the blue. There is usually a lead-up when it comes to engine issues, and if you know the telltale signs can help you catch them early and prevent them from causing long-term damage.
- Loss of power, excessive engine heat, or a sluggish feel when accelerating can indicate the engine is sumping.
- If you hear a “clunk” sound when putting your bike into first gear and/or stiff gear changes, it can indicate problems with the transmission.
- If you can smell oil or you notice patches of oil underneath your bike, this may indicate an oil leak. The most common spots for an oil leak are the rocker box gaskets and cam chest seals.
- If you hear any noise coming from the valve train, it could be due to inconsistent oil delivery and/or the hydraulic lifters not maintaining pressure properly.
Common Milwaukee 8 Engine Issues & How To Fix Them
While the M8 engine has been a game-changer in the world of motorcycles, with reduced vibrations, improved power, and more efficiency—it isn’t without its issues. Below, we’ve outlined the most common M8 engine issues and how to fix them.
Excessive heat
One of the most common issues riders are experiencing with their M8 engine is excessive heat. The increased heat levels can be a problem, especially in hot weather. It can lead to discomfort and put unnecessary stress on components in the long term.
The best way to fix the excessive heat problem is through prevention. Always keep up with maintenance and regular servicing. If you still find that excessive heat is a problem, aftermarket engine guards or heat shields can help.
Engine vibrations
The M8 engine was designed specifically to reduce vibrations compared to previous iterations, like the Twin Cam engine. Some riders still report excessive vibrations, however, especially at higher RPMs.
The best solution for this is to check for loose engine mounts or any other components that might be contributing to the vibrations. If you can’t find anything, it may need a balancing and tune-up at a professional workshop.
Transmission issues
Although it doesn’t seem as widely reported as some other issues, some riders are having problems with their transmission on bikes with an M8 engine. These issues can range from difficulty shifting gears to grinding noises.
Regular maintenance helps prevent any transmission issues. If the problem persists, we recommend going to a professional technician who specialises in Harley-Davidson motorcycles.
Oil consumption
Some riders have reported a higher-than-usual oil consumption with their M8 engine. This isn’t normal and could indicate that there is an issue with the oil, oil tank, or engine itself. While occasional oil consumption is normal, excessive consumption is a sign of underlying problems.
The best solution to oil consumption problems is to get ahead of it. Regularly inspect your bike’s oil levels and change the filter as instructed in the owner’s manual. If you notice any signs with the oil, contact a professional for repairs.
Professional Harley Davidson Servicing and Upgrades at Taverner
Taverner Motorsports has been in the business since 1975. Over the years, we’ve seen every combination of problems for all makes and models. So, whether you need a team for routine servicing, repairs, or upgrades, you can count on us. We pride ourselves on our experience, being reliable, and timely.
At our workshop, we’ve also got a specialisation for Harley Davidson motorcycles. We have extensive experience with Harleys, whether you’ve got a Twin Cam engine or running with an M8.
At Taverner Motorsports, we also offer M8 performance upgrades. It’s a fantastic engine, but we believe there is always room for improvement. We can tailor the engine to suit your riding style. Whether you’re looking for camshaft upgrades, piston and ring upgrades, or anything else, the Taverner Motorsports team has you covered.
If you have any questions about our Harley-Davidson performance upgrades or M8 engine enhancements or want to book a service, contact us today and request a quote. We’d happily answer any queries and help you achieve the motorcycle of your dreams.