Strange Engine Knocking

[JamieNeve]

Hi guys,

My top end has inherited a strange rattle/knocking sound which behaves very strangely, i'll do my best to describe it here:

Basically, when the bike has been left for a few hours, upon starting up for the first 2 seconds the rattle will be present, the second I rev it a tiny bit it stops. The bike then has all the power it should, and rides lovely. After riding for around 5 minutes and the bike is warm, the rattle then returns, and is constantly present until the bike is stopped and left to sat for a while again. Whilst riding with the rattle, when opening the throttle, the bike feels like it has no power whatsoever, and struggles climbing through the revs. The rattle is far more noticeable at higher revs, but also idle.

The cam chain was replaced at the weekend as I thought it was this, but it is still present following this.

The rattle sounds like it is coming from the top left of the top end but I am not sure.

Any ideas would be appreciated,

Jamie

[RedexRobB]

My first thought was the cam chain. Get the rocker cover off and have a good look round and check the clearances. Check the cam lobes for wear too.

[JamieNeve]

I thought that too,

Interestingly, before replacing the cam chain I seem to remember the noise was always present, and with the new cam chain it is now doing the whole on/off thing.

Valve clearances were only done in June, but will give them a check over,

Thanks Rob

[banner001]

you might want to check your rocker arms for wear as well, this can cause a tapping sound.

[zimm]

Ht lead for #1 or #2 arcing to the head/cam cover.

[zimm]

Rocker arms is a very consistent knock.. In that its just there all the time

[noelb]

Does it sound Internal? Check all the daft other stuff too, loose exhaust, random brackets etc. A blown exhaust gasket can sound like a weird knock as well...

[JamieNeve]

Ht lead for #1 or #2 arcing to the head/cam cover.

Interesting point to consider, will check on this too!

[banner001]

A blown exhaust gasket can sound like a weird knock as well...

ive had this too, couldnt find the source of the sound but it sounded top-end, i had removed the engine to get to the cams, no wear/damage on them, replaced the exhaust gaskets at the time and the sound went away...

[JamieNeve]

A blown exhaust gasket can sound like a weird knock as well...

ive had this too, couldnt find the source of the sound but it sounded top-end, i had removed the engine to get to the cams, no wear/damage on them, replaced the exhaust gaskets at the time and the sound went away...

Didn't consider this either, would this cause a large lack of performance though? I know it messes with the back pressure etc. but wouldn't have thought it would cause such a large difference.

Will get some more exhaust gaskets on eBay tonight!

[JamieNeve]

Just thought I'd update the post so people know what happened...

Turned out to be a blown exhaust gasket, thanks a bunch to cargo, noelb and Banner! So happy to have my bike back sounding great, and at the cost of £4 for the new gaskets!!!!

Cheers for the help everyone

[Top-shaggy]

Thanks for posting the result - great to know the outcome and that your sorted out )

[noelb]

Good to hear dude!