Sprocket Nut Sheared

Ayrtonf7

Well lads!

The bike stopped about 10 minutes short of work this morning due to a loss of drive. Wasnt really sure what it was at the start but my boss let me go out and take a look at it this morning and it looks like the bolts that stop the sprocket from freely spinning have completley sheared!



Looking into sourcing the parts now but because Im in Ashbourne its proving a tad difficult! Any idea what couldve caused this though ?

Its off a CB250 Nighthawk

CJhaughey

Ayrtonf7 wrote: »

Well lads!

The bike stopped about 10 minutes short of work this morning due to a loss of drive. Wasnt really sure what it was at the start but my boss let me go out and take a look at it this morning and it looks like the bolts that stop the sprocket from freely spinning have completley sheared!



Looking into sourcing the parts now but because Im in Ashbourne its proving a tad difficult! Any idea what couldve caused this though ?

Its off a CB250 Nighthawk

Didn't you have problems with these before?

Wossack

not good..! got them from cityspares recently enough I think yea?

cant imagine what would cause that.. missing cush rubbers or something?

though them being from cityspares, they prob werent new? so who knows the history of them, or what they came off of? (could have been weakened from whatever caused the bike to wind up being broken by cityspares in the first place?)

weird though - never seen that before

Ayrtonf7

CJhaughey wrote: »

Didn't you have problems with these before?

Yeh. When the chain came off the sprocket it destroyed the threads and nuts. I replaced them though shortly after and have been grand every since.

Wossack wrote: »

not good..! got them from cityspares recently enough I think yea?

cant imagine what would cause that.. missing cush rubbers or something?

though them being from cityspares, they prob werent new? so who knows the history of them, or what they came off of? (could have been weakened from whatever caused the bike to wind up being broken by cityspares in the first place?)

weird though - never seen that before

Yup Id say about 6-7 weeks ago. They were brand new and still in packaging. Somebody had ordered them in and had never came to collect em so I got dibs. They wernt OEM though so maybe that had something to do with it ?

Was just talking with my dad there as well. He cant believe it either, no idea what happened.

Max Headroom

Humour me...how are they mounted..i cant work it out by the picture..i'm assuming that the sprocket mounts behind the nuts...but whats the smooth part behind the flange....

OK..looked on CMS...so the sprocket is held on by a large washer and circlip , right..????....did you have these fitted..??

Ayrtonf7

Max Headroom wrote: »

Humour me...how are they mounted..i cant work it out by the picture..i'm assuming that the sprocket mounts behind the nuts...but whats the smooth part behind the flange....

OK..looked on CMS...so the sprocket is held on by a large washer and circlip , right..????....did you have these fitted..??

The smooth part fits into a hole on the wheel. There just there to transfer the drive from the rotating sprocket to the actual wheel. Its the circlip and washer that hold the sprocket on and yup I had both of them on.

I believe they may have just been bad quality. After looking at the bolt closer it appears that the threaded section and smooth section are actually two different pieces (each with half the flange on one end) welded together. The weld wasnt strong enough and they just ripped apart.

CJhaughey

The fact that they were spurious has a lot to do with it in my opinion.
Is your chain adjusted correctly and not too worn, if there is a lot of slack in the chain it can lead to big loadings on things as it flaps about.

Ayrtonf7

CJhaughey wrote: »

The fact that they were spurious has a lot to do with it in my opinion.
Is your chain adjusted correctly and not too worn, if there is a lot of slack in the chain it can lead to big loadings on things as it flaps about.

I replaced the chain, sprockets, swing arm and a sprocket mounting bolts when the chain jumped off last time so I don't think it was that. The chain was a tad bit loose but definitely not hanging off. I normally adjust it once a week so it wouldn't have been off by much.

Think ill just put it down to low quality parts. I think ill be sticking with OEM for anything non-consumable.

CJhaughey

Ayrtonf7 wrote: »

I replaced the chain, sprockets, swing arm and a sprocket mounting bolts when the chain jumped off last time so I don't think it was that. The chain was a tad bit loose but definitely not hanging off. I normally adjust it once a week so it wouldn't have been off by much.

Think ill just put it down to low quality parts. I think ill be sticking with OEM for anything non-consumable.

Check your sprocket alignment as well, after fitting a new swingarm it might have moved a tad.

Max Headroom

also check that the gearbox output shaft isnt bent..