Why Do Harleys Clunk When Shifting Gears?


If you are reading this, you probably ride a Harley and are wondering why it makes a loud clunking noise when you shift it into gear. I’ve test ridden many Harley Davidsons over the years, and every single one of them made that clunking noise when shifting. There is a reason for this.

Harley Davidson motorcycles make a loud clunking noise when shifting into gear because they have dog ring gearboxes instead of a synchromesh ring. The clunking noise that a Harley makes when shifting into gear is normal, but the clunking can be exasperated in cold weather or by a too high idle speed.

While some riders love the clunking noise a Harley Davidson makes when shifting gears, other riders no not like it all. While I don’t mind the noise, all I want to know is whether it is bad for the gearbox. Let’s find out.

Why Harley Davidsons Clunk When Shifting into Gear

I’ve not ridden a Harley that does not clunk when shifting into gear from neutral. And I’ve ridden more than 20 Harley Davidsons over the years. I’ve also not read of many Harley owners that claim their bike does not clunk when shifting into gear. Even the HD dealers say it is normal. There are several reasons for this.

Harley gearbox clunk when shifting gears due to the design of the dog ring gearbox

There are a couple of characteristics that may cause clunking when a bike is shifted into gear and Harleys have all of them present. Harleys have what is referred to as dog ring gearboxes. Without getting technical, a dog ring is a mechanism that helps the gears mesh together between shifts. Dog rings are used in race cars to ensure fast (and often clutch-less) shifting, as opposed to leisurely smooth shifts that synchromesh rings allow in road cars.

Basically, how it works, is the dog rings are mounted on the gears and have large recesses (detents) on the sides that ‘catch’ the output gear and match the speed before meshing the gear teeth. It allows for quicker shifts, but are more aggressive than gear shifts with synchromesh.

While many motorcycles employ dog ring gears (due to the engineering of sequential gearboxes), big V-Twin engines (like all Harley Davidson motorcycles) with their high torque delivery have larger diameter gears and output shafts. These heavy gears result in more inertia with the resulting momentum keeping the shafts spinning when the clutch is disengaged.

Large V-Twins with high torque will clunk more than an inline-4

Higher rotational weight of the large gear set shaft results in more clunking noise. A Japanese inline-4 sports bike may also have dog ring gears, but everything is smaller and there is less torque, so the clunking is also less severe.

The clunking sound that a Harley gearbox makes is often worse in cold weather due to the friction between the clutch plates in the thick transmission oil. Even with the clutch lever fully pulled in, the input shaft may still be spinning fast. Combine this condition with a too high idle speed for extra clunkiness.

Is it Bad for My Harley When it Clunks into Gear?

In short, no it isn’t. Most (if not all) Harleys clunk when shifting gears. I’ve experienced this on all the Harley I’ve ridden and I’ve confirmed it with the experience of countless HD owners on internet forums. Only a handful of riders claim to have softened (or even eliminated) the clunk-shifting.

If you are still unsure, listen to the clunk just before this Harley Davidson Seventy-Two pulls away in this official HD commercial at around the 2:00 time stamp. If that clunk was not supposed to be there, I am pretty sure a company who spends millions on engine acoustics would edit that out.

While all Harleys clunk when shifting into gear and it is totally normal due to the design of the gearbox, there are some factors that can cause excessive clunking which can accelerate the wear of the gearbox.

If the incorrect oil is used in the transmission (especially in cold conditions) the clutch plates may not totally disengage when the lever is pulled in. This means the output shaft will still be spinning with the engine as you slam into first gear. If the idle is too high, it can also augment the clunking if the clutch plates are binding.

How to Prevent Excessive Clunking in Your Harley Gearbox

The best thing you can do to avoid premature wear of your Harleys gearbox is to use the correct synthetic gear oil that was designed for large V-Twin engines. Amsoil Synthetic V-Twin is recommended and conveniently available on Amazon in gallons or quarts (see Amsoil Synthetic V-Twin).

While riding, try to shift into the next gear faster. If you wait too long to shift, after you’ve pulled in the clutch lever, the engine and gearbox speed will differ too much and result in a louder clunk to match the speeds of the gears that need to mesh.

When shifting into first gear from neutral, the severity of clunk can be minimized by taking a little more time between pulling in the clutch and dropping the bike into gear. This gives the internal gears and shafts time to slow down before having to engage with the stationary first gear. If your idle is too high, make sure to adjust it to the correct speed.

In cold whether, the higher viscosity of the gear oil may make the clutch plates bind together. If this happens, try the following: Start the bike, pull in the clutch lever completely, blip the throttle once, and then let the bike idle for at least 5-10 seconds with clutch pulled in completely. Now shift into first. The throttle blip will hopefully disengage the clutch plates and the wait will allow the output shaft to slow down.

If your clutch is not properly adjusted, it may not fully disengage when you pull in the clutch lever. This will also result in the output shaft spinning with the engine when you shift into gear. Make sure your clutch lever has the proper amount of free play as per the owner’s manual.

Finally, if you really can’t stand the loud clunking when shifting into first gear, but you simply have to ride a Harley, then start the bike in first gear (with the clutch in of course) instead of neutral. Just remember, the bike will move when you let go of the lever!

So are Harleys any Good?

Harley Davidson motorcycles are just different from other bikes. There are many things over the years that they could have ‘improved’ (modernized) to make the Harleys perform better. But many would argue that it would dilute the heritage of the brand. I don’t have a strong opinion either way, but one thing that I do know is that every time I get onto a Harley, none of that matters.

Related Questions

On the topic of gear shifting and clunking noises, have you ever experienced the situation where your bike starts okay in neutral, but dies when you shift into gear. If so, check out why in this post.

Harley clutches are very durable, but how long should the average motorcycle clutch last? Read more here to find out.

Francois Steyn

I've been riding motorcycles since I was in school and have traveled thousands of miles on various bikes through more than 10 countries. For more info, check out my about page: https://adventurebiketroop.com/about-us/

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