Engine noise

 hey there i have Yamaha DT175 bike from 2001.  Its pretty new and i bought
it new. I noticed that it makes noises when its idiling and when it has low
RPM's. Its like clicking sounds sounds like metal clases.. its not loud! but
it still doesn't sound normal.
Do you have any ideas what it could be?

 

 
jimmy joe wrote:

If it's an air-cooled 2-stroke, the piston rings will make a clashing
sound as they pass the exhaust port. 2-strokes don't have an exhaust
valve, they have a big oval shaped hole that the piston blocks off as
it comes up on the compression stroke. The piston ring bulges out into
the port and makes a clashing noise while the piston goes up, and it
does the same thing when the piston goes down on the power stroke. Air
cooled 2-stroke engines are noisy. But I like them.
I can't get an inexpensive new 2-stroke dualsport bike here in the
USA. You must be in Australia or New Zealand?

 Thanks for your answer.
ive asked quiet a bit of people what could be wrong.
ive heard that it could be the spark timing and now you say its that its the
piston rings...
If i check it all then i couldn't be wrong!
i live in denmark... i think the only places DT175's are sold is in denmark
and in australia

 
jimmy joe wrote:

Piston ring clash and cylinder fin "ringing" make air-cooled 2-stroke
engines very noisy, even if they have a quiet exhaust system...

If the spark timing is too far advanced, your engine will make a
tinkling noise that sounds like a poppet valve has too much clearance.

That tinkling noise is called "pinging" in the USA, the British call it
"pinking". But 2-stroke engines don't have poppet valves to make the
noise.

Pinging occurs under heavy load and part throttle conditions. You would
have to be moving for the engine to ping. If light pinging goes on for
a few minutes, you will see little black or brown specks on the spark
plug insulator nose.

If pinging goes on for very long, you'll start to see little shiny
balls of aluminum from the melting piston on the spark plug. I have
actually burned holes in 2-stroke pistons from not knowing what pinging
was. I was using the wrong heat range spark plug to keep from fouling
the normal spark plug. On the freeway, the "hot" plug got too hot, and
the fuel/air mixture ignited too early...

There is another noise like pinging, but it's louder. It's a loud
clattering sound that occurs when you have too much oil or very low
octane gasoline in your premix. It's called "detonation". Instead of
the mixture igniting too early as in pinging, when an engine's fuel/air
mixture detonates, it explodes all at once...

Even if you have an injector pump like Yamaha has, you can still get
too much oil injected into the crankcase and the low octane oil (it
really doesn't even have an octane rating, it will have a cetane rating
instead) will auto-ignite from the compression and heat in the
combustion chamber, just like diesel fuel in a diesel engine...