Drive chain catching on the back of the chain case

[JSF]

Hello all

A query I'm hoping someone can shed a little light on which I've noticed having done more miles- essentially the drive chain is rubbing on the back of the chain case and making it's own groove in the alloy! I can't quite fathom it from the manual but it's like there's a spacer missing or that something is misaligned.

Has anyone ever heard of this? The gearbox has been out recently so could We have made a sows ear in refitting it? (Everything looks and works ok to my untrained eye)

Any suggestions gratefully received and thanks again in advance

John

[a10 gf]

Hello, I made some 'nice' grooves once upon a time, fitted the wrong type of chain (was some kind of heavy duty chain), so first of all double check what kind of chain is fitted.

[muskrat]

 I agree with a10gf, many moons ago I fitted an O ring chain that fowled the inner primary. It didn't leave the shed.
Cheers

[JSF]

Thanks both - will check this out but the chain looks to have been on the bike for years so fear it's since we've had it apart!

[bsa-bill]

Hi John - if we are talking about the primary chaincase (you did mention alloy) and swinging arm models? is the wear on the rear or the back of the chaincase (does that make sense) if the rear then probably you need a link or half out of the primary chain, if it's the back ( nearest the engine and gearbox) have you replaced the little spacer or washer/s between the lug on the chaincase and the frame (the chaincase lug goes inside the frame)

all the best - Bill

[duTch]

  By your wording, it sounds like you've investigated, but-.......... (and you do mean FINAL drive, not Primary??)
If you haven't already done so, maybe employ a mirror to look along the chain, and up under(one of those oversize dentist ones from auto shop are handy), get it on the centre stand, remove the chainguard if necessary, and turn the wheel. you should hear/see something scraping.....??
 Wouldn't a spacer(other than necessary for the natural gap) between chaincase and frame make it worse??
 Isn't there a spacer between the inner case and crank-case?    Maybe that's missing?? or maybe needs (thicker) one??

 also check that the sprocket nut is done up tight, a loose one of those would allow the sprocket/chain to float over onto the primary...??
 
 I had a similar but different thing, but it was the con-link had caught the corner of the chainguard
 good Luck, cheers duTch

[chaterlea25]

Hi JSF
If its the primary chain rubbing??? then its likely that you left out spacer/washers between the frame and inner primary case bottom mount near the footrest ???

HTH
John

[JSF]

Thanks for the replies and additional input - I'll take another look and update. 

For clarity, it's a swinging arm bike and it's the drive chain that's catching - as you look from the rear of the bike along the chain, the chain is too close to the LHS (at the engine end) and is cutting a groove in the back of the engine casing! Almost like to front sprocket is protruding too far (but the chain run looks fine) so the outside of the drive chain is getting covered in shiny alloy!

I'll try a few of the ideas and as above report back on progress!

Thanks again

John

[a10 gf]

and is cutting a groove in the back of the engine casing

You may have some sprocket alignment problem, but here's the result of my 'reinforced' large chain experiment! But only cosmetic harm done.

[duTch]

For clarity, it's a swinging arm bike and it's the drive chain that's catching - as you look from the rear of the bike along the chain, the chain is too close to the LHS (at the engine end) and is cutting a groove in the back of the engine casing! Almost like to front sprocket is protruding too far (

Yup JFK, to reiterate, maybe not, but check the G'Box sprocket nut, and I think you mean Chain case

[Topdad]

As per Dutch's thought i'd check the final drive g/box cog for tightness,or it may develope  into a bigger problem. never tried but you may be able to insert a large flat screwdriver or bar to see if you could prise the chain and cog inwards ,don't go mad and damage something else but if you can see it move you'll know how to sort it, best of luck, BobH