Head gasket leak at sparkplug causing oil weep?

[JL]

Another problem I thought I'd put into a new post:



This weep has recently started. Pulling plug 2 (RHS) shows the thread is pretty oily.


Eeew.

Any ideas?

[HansJ]

My bet is valve cover gasket, head gasket not so likely.

[Mincehead]

Yep me too,VERY likely just the cam cover sealing gasket.I give you warning,it ain`t cheap from Mr Yamaha though!

[JL]

Thanks fellas, that makes sense. The valve cover gasket looks ok, but I think the culprit is the sparkplug/coolant pipe gasket. Thanks for pointing me in the right direction! Funny how these two parts aren't shown in the parts manual! (Perhaps they come with the valve cover?) Might try a little bit of high temp rtv around it on re-assembly.

[Mincehead]

Neither the spark plug rubber cover nor the seal on the coolant pipe hold back oil JL,if your coolant stub O ring was allowing coollant past it would show as a drop in coolant level in the radiator or header bottle,you might even see green or blue coolant leaking(depending on the colour of antifreeze you use).
The rubber cover that`s secured on the HT lead and pushes over the plug is simply there to stop water and road grime ingress.If it wasn`t the risk of such grit and crud getting into the combustion chamber would be high whenever you took a spark plug out.
I`m guessing it`s that cam cover gasket.

[JL]

Neither the spark plug rubber cover nor the seal on the coolant pipe hold back oil JL,if your coolant stub O ring was allowing coollant past it would show as a drop in coolant level in the radiator or header bottle,you might even see green or blue coolant leaking(depending on the colour of antifreeze you use).
The rubber cover that`s secured on the HT lead and pushes over the plug is simply there to stop water and road grime ingress.If it wasn`t the risk of such grit and crud getting into the combustion chamber would be high whenever you took a spark plug out.
I`m guessing it`s that cam cover gasket.

I'm pretty sure I see where you're coming from, but my valve cover gasket just seals around the outside perimeter of valve cover - if it had a leak, wouldn't it be apparent by seeing oil seeping on the outside rather than out through the spark plug drain hole? What I meant by the spark plug/coolant gasket part is circled below:


Couldn't see these listed in the parts manual...

(Funny, mine doesn't have the rubber line in the middle)

Finally found them in the workshop manual though...

Must come as a set in the AUD $74 I was quoted when I asked the parts man prior to undertaking the valve clearance check. And he said I could probably re-use the current one). I think I'll start worrying about it after I get a quote for installing new inlet valves, as that's a bigger saga right now

Thanks for your quick replies guys.

[Mincehead]

The RIGHT seal/gasket comes with `bridges` securing the sections for sealing around the plug tunnels and the coolant stub pipe.You need to cut those sections from the main body of the seal then use the lightest `lick` of clear silicon in four places around their periphery to keep them in place in the recesses of the cam cover.Too much silicon oozing out is VERY risky as it`s a bu**er for getting into oil galleries.
I`ll give you a tip,if you can detect any perishing of the seal around it`s outside edges,while looking at it still on the bike,it needs to be replaced if it`s disturbed.
Ahaaaaaaa,here you go a picture of one,in this case from a company I`ve used a fair bit WEMOTO:

http://www.wemoto.com/bikes/Yamaha/TRX_ ... et_-_Seal/

See the bridges you cut away as I described?
Here`s their full parts listing:

http://www.wemoto.com/bikes/Yamaha/TRX_850/97-99/

[JL]

A-ha, that picture helps explain things - thanks!