main crank drive sprocket teeth broken

[marcus243]

hi i need some advice from someone that knows more than i do about xs650 engines.I am in the middle of a rebuild and i found one just teeth broken on the crank sprocket,what i was wondering should i change the sprocket or the whole crank?
are just leave its only one teeth.please help

 

[jamesgs4]

Just replace the sprocket.

 

[XSRob]

Welcome marcus243. Not sure where you will find a sprocket. May be easier to replace the crank assembly but make sure you keep the same rod number. From your other post your rods should be 256 so keep clear of 447 and 533 rods!

 

[jamesgs4]

oops, i read it as main chain drive sprocket.

 

[XSLeo]

Maybe someone that has a few cranks can spare a sprocket. Ebay may have one.

 

[marcus243]

thanks i will look into that

 

[grizld1]

If you replace the sprocket, you'll need to degree the cam and may need to press off and move the cam sprocket; the position of the crank sprocket influences valve timing, and a small change in position can make a big difference.

Bear in mind that the tooth on the sprocket broke for a reason, and all the reasons I can think of are likely to have caused other damage as well, less obvious but equally severe. As XSRob suggests, you may be better off replacing what you have with a good used crank.

 

[XSLeo]

Aren't the sprockets keyed to the crank?
If so wouldn't splitting the crank, swapping the sprockets, pressing back together, be ok?
If keyed they only fit on right?

 

[XSRob]

Thats what I was thinking but what do I know

 

[Punkskalar]

Which sprocket again? I have a bunch of crank parts here, take a picture and I can match it up for you.

 

[marcus243]

thanks anyway got a complete crank off ebay the other day , should be here before xmas i hope

 

[XSRob]

I'd be interested to see how the crank parts go together as never delved that deep.

 

[XSLeo]

I helped rebuild two, I cant recall if the sprocket is splined and keyed or just keyed. I think it does both. When you rephase the crank you need to cut a new key notch in the sprocket hub. Three splines around.