Knock in pit bike engine

[locko90]

When I push the bike in neutral while it's not running it's making a knocking sound from somewhere at the front sprocket,

What could this be?

 

[my67xr]

Can you upload a video with the noise ?

 

[locko90]

Yeah man I should be able to get one up by tonight

 

[locko90]

heres that vid of the sound man, what do u reckon it could be? also the knocking sound is louder then that after I ride it for a while.
[video=youtube;jUHqNeQEXzo]https://www.youtube.com/watch?v=jUHqNeQEXzo[/video]

 

[locko90]

probably time for a new engine ? I think I can get a 2nd hand one pretty cheap off a mate.

it seems to ride fine, but theres this knock, maybe I should run thicker engine oil?

 

[my67xr]

So when you were rolling it back and forth then was it in neutral ?
It sort of sound's like there's a fair bit of play between the front sprocket and the output shaft.
I couldn't really hear what you were saying in the video, but was it louder when the chain was tighter ?
How much slack is there in your chain when your full weight is on the bike?

 

[locko90]

Yeah it was in neutral. I think your right about it have a lot of play between the front sprocket and the output shaft.

Yeah it's louder when the chain it tighter.

There is a fair bit of slack in the chain when I sit on it. I'm all ways adjusting it.

What do u reckon I should do mate ?

 

[my67xr]

Take the chain off (undo the joiner link and remove) and run the chain over a piece of rod, watch the chain for any tight link's.
If it doesn't bend as smooth as the rest at certain points then that could be the problem
Also check the condition of the front and rear sprocket's,
and try moving the output shaft on the engine and see if there is any noticeable movement, forward and back mainly.
The seal would most likely be leaking too if there is excessive movement there.

Turn the sprocket around with the chain off and see if the noise is there still too.