enginew rattle at startup

Ish · 27 Apr 2013 at 21:30

Hi

When I first start my bike I get a rattling sound that lasts for a few minutes. After that you can't hear it at all. If the bike is left switched for over 15 minutes you will slightly hear the rattle on startup but like I said worst case which is when the bike has been left overnight the rattle lasts for a few minutes.

It doesn't change if I dip the clutch. It sounds like it is from outside the engine rather than inside it.

Any ideas on what it could be?

My bike is a 51 Yamaha Thundercat that has done 24k miles.

Incinerat0r · 27 Apr 2013 at 23:37

Is it something that's just started recently? If it disappears after the bike has been running for a few minutes then that would suggest only when it's cold. Can you elaborate on "from outside the engine" ?

.one. · 28 Apr 2013 at 01:37

Maybe a shim rattle when cold.

Ish · 28 Apr 2013 at 10:27

I've had the noise for a few months.

By outside the engine I meant that the noise seems to be coming from something attached to the engine rather than from inside it but I know sounds can be misleading.

The cam chain tensioner has been suggested.

I also forgot to mention that the noise starts about 5 seconds after my bike has started from cold.

Incinerat0r · 28 Apr 2013 at 10:55

The CCT is certainly worth checking, my 00 R6 was due a top end service around the 25k mile mark so that could be something else to look into. It could also be nothing to worry too much about, my previous R6 rattled a bit and I got quite paranoid about it but googling around it seemed to be fairly common

MatteH Oxford · 28 Apr 2013 at 11:36

Ish said:
The cam chain tensioner has been suggested.

Does the noise go away when you hold the revs slightly up from idle speed, say around 1800-2000Rpm?. If so, it'll likely be this my blade used to do it until I renewed the CCT

Dogbreath · 29 Apr 2013 at 14:47

Could be an exhaust leak or loose spark plug, which would make the noise more "external".

Cam chain tensioner issues don't usually get better with a warm engine, though I suppose it's possible a sticky tensioner could free off when it gets hot. Easy enough to tell; if you remove the bolt from the end of the tensioner (10mm hex head) there is a screwdriver slot behind it which is normally used to draw the plunger back when removing/installing the tensioner. However it can also be used to apply extra tension. Apply a bit of extra tension via the screw whilst the engine is running and if the noise disappears you have found the problem.

wazza300 · 29 Apr 2013 at 17:54

brake disc rattle? ive had that before

MatteH Oxford · 29 Apr 2013 at 19:55

I forgot about twiddling the tensioner, I did that on mine to confirm it using a jewellers screwdriver. I must admit it that I didn't think it would be the tensioner as it got much better once the bike was to running temperature.

My bike piston slaps a little when cold but it is most noticeable when you give the throttle a small blip, tensioner noise should go away with a throttle blip and then come back when the bike is idling again.

Ish · 29 Apr 2013 at 22:40

I'm going to give the tensioner a try first and will report back.

wazza300 · 30 Apr 2013 at 13:38

if it is the tensioner try googling ape manual camchain tensioners,you have to adjust them yourself but last much longer than the factory units

EDIT: another thing to check if your bike has a lower fairing is some rubber bungs riveted onto the exhaust underneath to stop the fairing touching the hot exhaust,they rattle like a tin can,ive wrapped some garden wire around mine and stopped the noise,its worth a check