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Unlike car engines, motorcycle engines don’t rely on cam belts for their valve timing – instead, they use cam chains.
And this episode is dedicated to demystifying not just cam chains but valve timing as well.
Tune in to discover:
- What a cam chain does, and whether it’s the same thing as a drive chain
- How an incorrect valve timing can destroy your engine
- 4 cam chain and valve timing FAQS – including whether a cam chain needs to be replaced
Transcript
Hello, and welcome to another episode of 30-minute Motorcycling – a podcast for those riders who are at the beginning of their own Dual Wheel Journey, where you’ll discover something new about how your motorcycle, moped, or scooter works – in less than 30 minutes.
Do you know what a cam chain is, and what it has to do with valve timing?
How often do you need to replace your cam chain?
And, since I brought it up, what is valve timing, and why does it matter?
I’m this episode, you’ll find the answer to all three of those questions – plus two more.
But before we get started properly, I’d like to point out that a cam chain and a drive chain are two different things.
Yes, they’re both chains, but a drive chain is exposed in the open, while a cam chain remains closed up inside the motorcycle’s engine.
Now that we got that out of the way, let’s talk about what a cam chain is.
A cam chain is a chain that is wrapped around the camshaft pulley at the top of the engine and the crankshaft pulley at the bottom of the engine.
This cam chain is absolutely vital for a fully functioning internal combustion engine – which brings us to the topic of valve timing.
Inside the engine, there are these small, thin metal pieces. These small, thin metal pieces are called “engine valves” or just “valves” for short.
They’re not particularly complicated design-wise – just a metal stem with a round shape at the bottom. But despite their simplistic design, they perform a key role in any well-functioning internal combustion engine.
And that role is to let fuel and exhaust gasses in and out of the engine at a specific time.
It doesn’t matter if you’ve got a 50cc Peugeot Speedfight 4 or a 900 cc Kawasaki Vulcan – at the bare minimum, every motorcycle engine has at least two valves – one for the intake and one for the exhaust.
So that’s a summary of what valves do – so what about valve timing? After all, that’s one of the things we’re supposed to demystify in this episode.
In just one sentence, valve timing is the exact time when the intake and the exhaust valves are supposed to open and close.
If they open at the wrong time, expect engine trouble. Serious engine trouble.
If one of the valves opens or remains open at the wrong time, the risk is that the piston will slam into the valve as it travels up inside the combustion chamber.
And since the piston is much, much bigger than the valves, the valves will be damaged severely if this happens – just like the law of gross tonnage states.
If the valve is damaged, it will bend, which in turn, means that the valve will not close properly, which in turn causes:
- A drop in engine performance
- Knocking noises
- Misfiring
So what about the cam chain? Where does it come into play?
Well, the cam chain makes valve timing possible – since it wraps around both the camshaft and the crankshaft pulleys, they’ll both rotate simultaneously – as long as the chain is wrapped around them, and the timing marks are aligned, the valve timing will be correct.
And that’s cam chains and valve timing demystified. But before we end this episode, let’s answer 4 FAQs about both topics.
Question #1: Do you have to change a cam chain?
If you know a thing or two about how cars work, you’ll know all about cam belts (AKA timing belts) – more specifically, you’ll know about the dreaded belt replacement you must do every 100,000 kilometers or 60,000 miles.
In that case, you’ll be happy, and even relieved to hear that a cam chain doesn’t need to be changed as regularly – generally, a cam chain lasts as long as the engine itself.
The only time you’d need to replace a cam chain is if it is in rough condition.
Question #2: Is there a difference between a “cam chain” and a “timing chain?”
Not much – apart from the choice of words, there’s no difference between a “cam chain” and a “timing chain.”
Question #3: What are some common symptoms of a loose cam chain?
Do you hear a rattling sound coming from your motorcycle’s engine? If you do, that’s the most obvious sign that your cam chain is too loose.
And finally – Question #4: How is valve timing set?
It depends on whether your motorcycle or scooter has a two- or a four-stroke engine.
For four-stroke engines, the camshaft controls the timing of when the valves open and close.
As for two-stroke engines, many have their valve timing set through port timing, although some use the same camshaft approach as four-stroke engines.
If you’d like to read more about port timing, I’ve included a link to an article on mecholic.com in the description for this episode that goes into more detail about it.
And that’s the end of this episode – we’ve demystified both cam chains, valve timing, and on top of that, we’ve covered some common FAQs about both of them.
I hope that you enjoyed listening, and above all, that you discovered something new.
Until next time, keep your helmet on, and your eyes on the road. Bye!
