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Discussion Starter · #1 ·
So I just bought a yamaha tzr50 to play around with, I noticed it has a strang sound when I drive, I know nothing about motorcycle, so I have noe idea what it can be. The sound comes from the engine under the seat somewhere I think, it is a bit hard to locate where the sound comes from.

Here is the sound:

also, does the engine sound healthy? I dont really know how it is supposed to sound. I notice I have 3x the acceleration at around 8k rpm as below 5k rpm.
 

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Take it apart man, your engine sounds like it is in self destruct mode. It's only a 50cc 2-stroke, it should take you all of one day to do it.


& make your next video outdoors and at idle, there is way more chance of hearing something relevant, were are listening for metal on metal sounds that you should never hear.
 

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Discussion Starter · #3 ·
Take it apart man, your engine sounds like it is in self destruct mode. It's only a 50cc 2-stroke, it should take you all of one day to do it.


& make your next video outdoors and at idle, there is way more chance of hearing something relevant, were are listening for metal on metal sounds that you should never hear.
Thank you for your reply.
im not sure it it will be to any help if i take it apart since I dont know what to look for.
What makes you think it is in self destruct mode?

The sound is speed dependant, it goes faster the higher the speed. The sound im wondering about is after the acceleration, the “wave” like sound. The metal like”click” or “pop” is also kinda strange.
 

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Hmm. Something sounds off. Here is what it should sound like.


 

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Thank you for your reply.
im not sure it it will be to any help if i take it apart since I dont know what to look for.
What makes you think it is in self destruct mode?

The sound is speed dependant, it goes faster the higher the speed. The sound im wondering about is after the acceleration, the “wave” like sound. The metal like”click” or “pop” is also kinda strange.
It's not a happy motor sound. It's a 2-stroke and from here it sounds like your piston is slapping the sides of the cylinder, at the very least that is a top end rebuild, meaning the engine needs to have the cylinder head and barrel pulled off so the piston and rings can be inspected and serviced.
 

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If it's any consolation, it's not a difficult service process once you know how to do it.
Your first purchase should be the Yamaha service manual for that bike, that will tell you how to do it.

... and it won't be the last time it needs to be done, the rest of the bike should out last more then one piston and rings.
 

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Do you mix the oil in the gas or is the oil separate? not familiar with 2 stroke bikes.
 

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Discussion Starter · #9 ·
It's not a happy motor sound. It's a 2-stroke and from here it sounds like your piston is slapping the sides of the cylinder, at the very least that is a top end rebuild, meaning the engine needs to have the cylinder head and barrel pulled off so the piston and rings can be inspected and serviced.
If it's any consolation, it's not a difficult service process once you know how to do it.
Your first purchase should be the Yamaha service manual for that bike, that will tell you how to do it.

... and it won't be the last time it needs to be done, the rest of the bike should out last more then one piston and rings.
So I must change the piston and the rings to make the engine work better then.

Im looking forward to learn about MC engines, so this will be fun.
 

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So I must change the piston and the rings to make the engine work better then.

Im looking forward to learn about MC engines, so this will be fun.
Inspecting is what you will be doing, what parts need replacing will depend on what you see when you get inside the engine. Other things you will be checking while you are in there will be the top and bottom end bearings.

I think your rings are stuck in the piston groves and that could be just from foreign material or it could be from damage to the piston.

.... Owner manual is useless for what you are doing you need the Service manual
 

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The bike in the video filled up at a gas pump, so I'm guessing he has oil injection and is not running pre-mix. One way or the other your engine needs 2-stroke oil in the fuel to work.
 

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Discussion Starter · #14 ·
Inspecting is what you will be doing, what parts need replacing will depend on what you see when you get inside the engine. Other things you will be checking while you are in there will be the top and bottom end bearings.

I think your rings are stuck in the piston groves and that could be just from foreign material or it could be from damage to the piston.

.... Owner manual is useless for what you are doing you need the Service manual

Alright, thanks, ill open the bike up this weekend and see what I can find. Any other advice on things to look for?
The bike has not been used in 3 years or so I guess there can be all kinds of things I should do with it to make it work properly...
I also notice it does not sound completely smooth while at idle, the sound is a bit unregular.
 

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You're going to need a small torque wrench, a replacement head gasket, replacement bottom end gasket and some engine coolant. Take lots of photos so you know how it goes back together.
 

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My guess is that the sound is a failed cam chain tensioner. Usually when those fail you get a lot of chatter. Generally they are just a little hydraulic ram that pushes against the chain. If thats the case, the motor is not in any mortal danger, its just noisy.
 

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Wait. Before you start ripping it apart, lets discuss your fuel. Are your running straight gas without 2 stroke oil? I had a Yamaha 2 stroke with a defective oil pump. I had to run 60: 1 premix for it to run right.
 

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My guess is that the sound is a failed cam chain tensioner....
:unsure: it's a 2-stroke engine with reed valves.


It's a 3 year old 2-stroke 50cc sportbike that sounds like a bag of hammers, the horrible noise will only get worse and the damage more extensive until it's fixed.

If you want something to practice on rip apart a chainsaw and put it back together again.
 

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Discussion Starter · #19 ·
Wait. Before you start ripping it apart, lets discuss your fuel. Are your running straight gas without 2 stroke oil? I had a Yamaha 2 stroke with a defective oil pump. I had to run 60/40 premix for it to run right.
I have not filled any gas on it yet, but I was told by the previous owner that I should mix it with synthetic 2 stroke oil.

how can I check the oil pump?
 

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Hmm. Is there oil in your oil resevoir? What color is it? If your oil pump/ injector isnt working right, or the premix is off, your bike will run like **** or not at all. Check out page 22 & 23. Is your fuel cock in the on position? Did you turn off the choke?
 
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