Cam chain rattle

I keep getting a constent rattle from the cam chain when under load and tick over but goes when going down hill, I've changed the spring and locking screw but when took old spring out it was longer than the new one from Yamaha and fear the chain has stretched.

Is a replacement a big job

The mileage is 13,800 or so and running 20w/50

The chain needs to be slack when you adjust it, (ie no load on it from camshaft, do it at top dead centre with both valves closed, it also helps if you push the spring & tensioner plunger in with you finger. When you have tightened up the locking screw check to see if its tensioned up, ie no stack on cam sprocket. If the chain is tight then the rattle must be from somewhere else. Strange it goes off when going down hill. Chain should not need changing after only 13800 miles

Keep getting different ways of adjusting the chain and no luck so far, I've adjusted it before with the chain tight and seen the chain when rotating go tight than slack again.

So
1) tdc compression stroke
2) adjust it when slack
3) push plunger and spring in with finger

Does the lock screw need fitting tight

sammyt80 wrote:Keep getting different ways of adjusting the chain and no luck so far, I've adjusted it before with the chain tight and seen the chain when rotating go tight than slack again.

So
1) tdc compression stroke
2) adjust it when slack
3) push plunger and spring in with finger

Does the lock screw need fitting tight

Tighten the locking screw with cross head (Philips) screwdriver whilst pushing in the plunger. Dont forget to do up lock nut. If this does not cure the problem its not the cam chain. Without hearing the noise its hard to diagnose. Sorry cant help further.

Thanks will have a try tomorrow if weather gets nicer, going to change oil as well I've put in 2cylinder 20w/50 in by mistake and thinks its struggling as its very thick and viscous and going to use 10w/40.

Found one cause, the cam chain tensioner lock screw the cylinder where stripped and literally just sat in there Got it back from garage and told them how to adjust and got it back and still a slight rattle but hay how going to leave for now, think it might need a new chain.

My lock screw is stuck, any tips on moving it, I have an impact driver but don't really want to use it. I could do damage, I was thinking about heating the head area around the screw. The timing chain may have a slight rattle but I'm sure it will run for a while, until my next service on it.
Any ideas, the screw looked like it had never been undone in the past, like everything else on this bike, it has never been touched.
Regards
Dave

Dave Weller wrote:My lock screw is stuck, any tips on moving it, I have an impact driver but don't really want to use it. I could do damage, I was thinking about heating the head area around the screw. The timing chain may have a slight rattle but I'm sure it will run for a while, until my next service on it.
Any ideas, the screw looked like it had never been undone in the past, like everything else on this bike, it has never been touched.
Regards
Dave

An impact driver is the only way, but make sure you have a good fitting bit. A bit of heat may help.

Cheers John, I will give it a go, hopefully soon there will be another T80 on the road, it's already legal, I just want to do a bit of preservation work while I've got the back wheel out, I can't find any major rust areas so i'll Kurust it, prime and spray the under frame, and Waxoil it.
Thanks again for your help and this site.
Dave

my cam chain tensioner was seized and the cam chain was making a lot of noise so I got some heat on the screw but be careful shield the surrounding area then gently tap it round don't be I to brutal with it