Loud rattle which gets worse as bike warms up - CBR 600 1988

[Nipedley]

Hey guys,

My CBR sounds fine on start up but as soon as she starts to get warm she develops a very loud rattle which you can hear over and above the general exhaust/engine noise.

The rattle gets worse the lower RPM and disappears at about 3k RPM

My initial thought was cam chain rattle, so I replaced the cam chain tensioner, unfortunately no change. While the bike was at an MOT I asked the mechanic and he thought cam chain too.

I guess my questions are 1) does this sound like cam chain rattle to you, 2) if it is, what is likely to be dead and need replacing as a result, and 3) is it easier/cheaper to just get a replacement engine from ebay (looking at £160 - £200)

I have had a look and a replacement DID timing chain is £80, then there's cam chain guides and sprockets, if those need repalcing too then the bill is going to be up over £160 quite easily I think. I also don't know what's involved in replacing a cam chain, presume splitting the case and such also will need a full gasket set, which are also pretty pricy?

[Nipedley]

Also, it's perhaps a slightly redneck answer to the question, but would fitting an APE tensioner help here (as there is more adjustment range than the OEM one can apparently provide), providing the timing chain sprockets and guides aren't too shagged out already.