Yz valve noise.

[glockman]

My 450 started making a very odd valve train noise today. The valves are all in spec the piston is about 15 hours old. The bike has about 200 hours with the original timing chain and tensioner. I'm thinking the timing chain or the auto decompress mechanism. Any ideas?

http://youtu.be/906lidcCgGk




Sent from my iPhone using Tapatalk

 

[jeeper]

Any ideas?

BUY A 2 STROKE!!!

 

[Chase39]

Have you pulled the valve cover off since?

 

[Greg]

The cam chain tensioner probably failed... The failure is fairly common, happened to me on a DRZ several years ago. Mine sounded just like your video. I replaced the factory automatic tensioner with an aftermarket manual tensioner. They're pretty cheap and easy to change, I wouldn't be too worried.

Here are some manual tensioners for your bike... - http://www.bigborethumpers.com/tensioners.html

 

[glockman]

Have you pulled the valve cover off since?

Yes. I took the valve cover off and checked the chain and valves last night.

I am going to replace the chain and tensioner today. They are both overdue.

 

[Chase39]

Let us know how it goes

 

[Tonkaman]

The cam chain tensioner probably failed... The failure is fairly common, happened to me on a DRZ several years ago. Mine sounded just like your video. I replaced the factory automatic tensioner with an aftermarket manual tensioner. They're pretty cheap and easy to change, I wouldn't be too worried.

Here are some manual tensioners for your bike... - http://www.bigborethumpers.com/tensioners.html

Greg is dead on. Definitely ditch the auto tensioner before it costs you a motor

 

[glockman]

Bought a new chain. Haven't decided on the tensioner. What is the advantage of the manual vs auto? The original has made it 6 years and lots of hours. How do you know how tight to adjust the manual type?


Sent from my iPhone using Tapatalk

 

[Tonkaman]

Auto tensioners have a reputation for being very unreliable. Even though your tensioner has lasted longer than most that just means its a ticking bomb. The biggest problem is one slip and the motor us trash.

Adjustment is easy just turn the tensioner in until you feel the chain dragging then back it off 1/4 turn and lock down

 

[Greg]

Auto tensioners have a reputation for being very unreliable. Even though your tensioner has lasted longer than most that just means its a ticking bomb. The biggest problem is one slip and the motor us trash.

Adjustment is easy just turn the tensioner in until you feel the chain dragging then back it off 1/4 turn and lock down

x2!

 

[glockman]

Out of convenience I picked up a factory tensioner. Installed it and a new timing chain. Fired it up and, no difference. So I started digging. Pulled the head and all the valves were present and not broken.
I turned the crank over and bingo, wrist pin was halfway out of the piston and sliding up and down the cylinder wall.
I took the parts to LMR to see if the jug is salvageable. Apparently this is common with Wiseco pistons. Due to no oil journals in the wrist pin they seize.

Total damage
Cylinder, piston, connecting rod.
The guy at LMR looked at my head and noticed two burnt valves and really wide contact band. All new valves and a head grind are in order as well.

Now I'm contemplating just selling it as is and buying a YZ250 2t.

 

[jeeper]

Now I'm contemplating just selling it as is and buying a YZ250 2t.

Yes.

 

[Tonkaman]

I would crunch the numbers but lean heavily toward a new purchase. Sounds hypocritical from me since I'm building a motor right now. I factored in all my other mods that I would have to do to a new bike and the fact that it will soon be a second bike. It will by no means be the cheaper solution tho

 

[glockman]

I'm leaning toward new cylinder, piston and rod. Ride that for next year, then redo the head. I still have factory shims in and the bike starts when cold with no issues. So the head should be good for another 20-30 hours. That spreads the pain out a little.

 

[glockman]

Had a wild thought today about pulling the motor from my TTR 250 and putting it in my yz frame. Then buying a YZ 250 2T like I have been contemplating. Now to take some measurements and see how hard it would be.