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When you're ready to kick off on that next motorcycle adventure, the last thing you need is the clutch to start playing up. Maybe it's making some funny noises, or it's stopped working entirely and your whole day of riding is shot.
But before you panic and start thinking about the cost of a brand-new bike, consider the last time the clutch oil was checked. The oil that a motorcycle wet clutch is lubricated with plays a huge part in clutch effectiveness and how it feels.
Keep reading and we'll run through everything you need to know about a motorcycle wet clutch.
First of all, don't stress if you have no idea what a wet clutch is. That's what articles like this are for! We'll start with the basics so you have all the info needed to get your bike running like a well-oiled machine again.
As you might already know, the function of the clutch is to connect the engine and transmission using friction and steel plates.
Wet clutches are just clutches that are lubricated in oil, commonly used in dirt bikes and motorcycles. Lubricating the clutch gives it a much smoother operation, especially in motorcycles.
Oil is very important for clutch performance. It affects the dynamic friction that you experience, or for those without an engineering degree, how the clutch 'feels'. Oils that don't have the right friction properties can make the clutch feel less consistent or 'loose' to put it another way.
Think about kicking off when a red light turns green. The quality of oil matters if you want to confidently pull away without the bike cutting out. Oils without the right friction can result in the clutch plates slipping in some cases.
Every engine oil is made from a base oil, with some performance-enhancing additives thrown in. There are three types of motorcycle oil, depending on the base oil that it's made from.
Mineral oil is derived from crude petroleum. Mineral oils are the cheapest of the bunch, and unwanted contaminants are removed during the refining process.
The drawback is they don't perform as well as synthetic oils. Because they flow through the engine slower, there is greater fuel consumption and worse overall performance than synthetic oils.
Mineral oils don't perform as well in extreme conditions and need to be changed more frequently than their synthetic counterparts. It's recommended to go with mineral oil for motorcycles with older engines or with a smaller engine capacity.
Semi-synthetic oils are ideal if you want something that can block oxidation and perform across a range of temperatures, but you don't want an oil that's fully synthetic.
Semi-synthetic oils combine mineral and synthetic oils, so you can get the best of both worlds. They're better than mineral oils but won't cost you as much as fully synthetic oil.
They also contain strong synthetic additives that enhance the oil's performance and even add some new features to the oil.
Fully synthetic oils are highly sophisticated and are best used for new motorcycle models. A bike with an engine capacity above 200cc should use synthetic oils.
Synthetic oils are the best of the bunch. They offer the best possible lubrication and protection for large engines that need to take a heavy load of stress.
They also last longer than the previously mentioned oils and give the best overall protection to the engine. The only major drawback is the cost. Fully synthetic oils are the most expensive option, so you will have to decide if the benefits are worth the price.
Synthetic oil can be used on a wet clutch, but you will definitely need to check that your motorcycle or vehicle of choice is compatible. Check with the manufacturer, or better yet if you still have the vehicle manual see what that has to say.
For example, some manufacturers recommend mineral-based oils for their wet clutch systems. With that said, let's go through the different types of synthetic oil.
Here are some of the main synthetic oils that are commonly used for motorcycles:
Group III oils are made from highly refined base oils, so they're not considered to be truly synthetic but more 'synthetic-like'. The benefit is they're less expensive than truly synthetic motor oil.
Unlike group III oils, group IV are considered truly synthetic. Highly resistant to thermal breakdown and more resistant to viscosity loss at high temperatures, they're widely considered the best motorcycle oils.
Group V oils are made from other synthetic base oils and are generally considered to be the most advanced type of synthetic oil. They provide the highest level of protection for motorcycle engines and transmissions.
Of course, always check that your bike is compatible with any type of oil. Shop for lubricant specifically formulated for wet clutches. Don't assume that any old oil will do the job.
There are a few benefits of using synthetic oil on a wet clutch. Synthetic oils provide better lubrication than conventional engine oil, which helps reduce friction and wear on the clutch system.
They also maintain their lubricating properties over a wider range of temperatures, particularly in cold weather. Synthetic oils flow and lubricate more effectively than normal oils in the cold, which reduces the chance of clutch slippage and makes for better overall shifting.
Synthetic oils have lower volatility than traditional engine oils, so they're less likely to vaporise and create deposits on the clutch components. That not only means better performance but it also needs less frequent cleaning, which is always a nice thing.
Synthetic oil does reduce friction but to a certain extent. Synthetic oils are specifically designed for better lubrication and protection than traditional oils. They're much better at reducing wear and tear on the moving parts of an engine.
They also contain friction modifiers that reduce friction between metal surfaces. This not only improves fuel economy but overall engine performance and life.
Does synthetic oil make wet clutches slip? Yes and no. First of all, the quality of the clutch itself and the driver's shifting technique can play a part in how smoothly the clutch operates.
But aside from that, using synthetic oils in the wrong way can result in clutch slippage. If you go from using a semi or non-synthetic oil to a fully synthetic oil, it might make the clutch slip. This is actually because the motorcycle's lubrication property will be too good because of the previous oil used.
The best way of avoiding a clutch slip is to make sure you're putting the right stuff in the bike. Is the oil okay for that particular motorcycle? What does the manufacturer say? Cheap oil can sometimes be reclaimed oil or carry additional additives, so be careful what you buy.
If you've checked that everything is A-Okay and slippage still occurs, sometimes you simply need to leave the bike overnight and then ride it gently for 40 kilometres or so. This is because new oil put into the engine can douse the clutch plates and they just need to spin to clear off any excess.
The best motorcycle oil for a wet clutch is one that is specifically made for the vehicle it's going into. So if you own a dirt bike, for example, get synthetic dirt bike oil. Just make sure that you get motorcycle oil that is specifically made for a wet clutch. You can't just buy anything and call it a day.
Look out for motorcycle oils with the specification label of JASO MA or JASO MA2. This indicates that they're specifically designed for proper lubrication and protection of wet clutch systems.
It's also recommended to use motorcycle oils with an API rating of SH, SG, or higher, as they're designed to provide better protection against wear and tear, corrosion, and oxidation.
If you want a recommendation that's a bit more specific, here are some of the best brands of wet clutch oil:
The important thing to remember is that wet clutch oil is useless if it's not made for your motorcycle. Just like you and me, it needs the right stuff put inside it to stay healthy.