Some engine problems cause your engine to run poorly – from engine overheating to “running rich.”

Other issues are more severe, so severe that they can cause your engine to stop running altogether.

Case in point – the engine seizure, which you’ll discover more about in this article.

Among other things, you’ll discover:

  • What an engine seizure is
  • 3 common reasons why an engine seizure happens
  • Differences between soft vs. hard engine seizures

What Is an Engine Seizure?

If your bike is running on petrol or gasoline, it has many small parts inside of it. It doesn’t matter if it’s an inline four-cylinder engine, a big V-Twin, or something else – it has these parts.

And these parts are designed to move in and out – from the crankshaft to the camshaft and the piston. 

But suppose that there’s something that prevents the moving parts from moving like they’re supposed to. What then?

Then, the engine can’t run because one or more moving parts are stuck.

3 Possible Causes for an Engine Seizure

1: Lack of engine oil

image of motorcycle oil dipstick

One of the reasons the engine’s internal parts can move in and out is lubrication, which is one of the jobs of the engine oil.

But if there’s not enough oil (or even no oil), it increases friction, which means the parts begin to grind against each other.

For some parts, like the piston, it might not even be able to move up and down through the combustion chamber if it doesn’t get appropriately lubricated.

And that means there’s no way to compress or ignite your fuel and air mixture – in other words, you’re not going anywhere.

So don’t skip the vital oil-checking steps during your next T-CLOCS pre-ride inspection – your engine depends on it.

2. Overheating

image of an overheating engine

Sure, the engine gets hot under normal working conditions, but there is such a thing as “too hot.” 

Remember – most of the moving parts are made from metal. When metal gets hot, it expands – and this expansion is permanent and irreversible. 

Let’s look at the intake valve as an example (pictured below):

image of engine valves

Notice how the shaft of these intake valves is almost the same in length?

There’s a reason for that – if this shaft is too long, the valve plate (the bottom part of the valve) is in grave danger.

It’s designed to open and close at specific points – it opens during the intake stroke and closes during the compression stroke when the engine piston moves up.

If the piston hits that plate during the compression stroke, it will permanently bend that valve so it won’t close again.

Fortunately, you can prevent this with a correct valve timing setup. But if the valve’s shaft has expanded because of overheating, valve timing won’t matter.

That heat expansion means that the shaft will protrude out longer than it should.

Fortunately, you can avoid this by ensuring your engine is cooled like it’s supposed to.

Want to get to the bottom of why your engine is overheating? Feel free to check out the 5 most common reasons for it here.

3. A fuel mixture that’s too lean

While running rich is certainly not ideal, running too lean (i.e., having a fuel mixture that contains more air than fuel) isn’t much better.

Some of the lean fuel mixture effects include reduced power and, for the context of this conversation, increased combustion temperatures.

Sound familiar? It’s just like the cooling problems we just looked at.

But even if the cooling system is working like it’s supposed to, a lean fuel mixture can cause the same problems as a non-functioning one:

  • Increased friction and wear and tear on the internal moving parts
  • Metal components expanding beyond their intended limit



Soft vs. Hard Engine Seizures


With a soft engine seizure, you might experience a sudden reduction in engine performance, often caused by a lack of lubrication.

But the good news is that this seizure is only temporary if you detect it early.

Even if the performance suffers, you can usually restart and run the engine again.

However, you can’t say the same thing about a hard engine seizure.

If you’ve got a hard engine seizure, it’s the result of prolonged overheating or a massive mechanical failure.

And in that case, the engine won’t even turn over when you try to start it.

Because of this, it’s not something you can fix with a can of WD-40 in 5 minutes.

Often, it might be necessary to do a complete engine overhaul to fix a hard seizure.

If you’re curious about what an engine overhaul is, check out the article about it here.