B12 engine new 3rd gear rattle

[Jdeac]

Hi all. Been out for a blast today. And the motor/gearbox has developed a rattle in third gear.

On power cant really hear it. But steady in third and deceleration you can hear it. 

Chain tension good, outputshaft bearing good.

What could be the cause of this?? And should I be concerned riding it.

[Jdeac]

I shall try that. I had only adjusted the chain this morning. After the bike had a good cleaning.

[Jdeac]

So dropped the oil today. As the noise almost seems like third is partially engaged. Put a magnet in the drained oil. And see pic

[Jdeac]

What part has let/letting go hear??

[clivegto]

6 minutes ago, Jdeac said:

What part has let/letting go hear??

Sprocket bearing possibley. Usually it's 2nd and 5th that goes on the dogs. 

[Jdeac]

@TonyGeeThat's was my thoughts. I've never stripped a motor before!

@clivegto if the sprocket/output shaft bearing had gone/going surely it would make the noise in all gears

[clivegto]

As Tony says bottom end can be split with out removing the top end so you best take it to bits for a look see yourself, I would. 

[Jdeac]

Ah crap. Hear comes a learning curve

[Jdeac]

Just been flicking through the manual on my lunch break. And looking at what needs to be done. 

Are there any specific tools I'm going to need. Clutch tool I know but anything else.

Cheers

[SiBag]

@fatblokeonbanditdid a nice writeup of how to change the gearbox without taking top end off. Off another form I think.

[Lachie04]

TIP: there's a bolt hole at the back of the case an at recess at the front to fit a 5-6mm nut and bolt to help pry the cases apart. I don't think they tell you that in the manual (thanks to @fatblokeonbandit)

 

[Jdeac]

Thanks for the tips guys. I shall probably pull the motor out on the weekend. Just do small bits in the evening after work until its ready to drop. 

Pulled the exhaust of tonight and the sump for a little look. I know there is loads I cant see.

But anyone see anything? The small lever part on the end of the selector drum has some material on it.

[Jdeac]

I get what your saying. 

And the parts are magnetic so steel. 

As above I'm just going to pull it apart slowly. I've never done anything like this before. So took a couple of pics. To see if there was anything that stood out.

After the sump was off I found a piece of metal about 2 ish mm long. Fresh metal one side and black in colour the other.

I'll probably put the motor in out of my project build for now so at least I will have a bike to ride. Then this one will (hopefully) get built for the project

[Jdeac]

Also anyone recommend a clutch tool. As I dont have one