Briggs 123600 rocker cover oil leak

[Mkala]

Hi all,

My father mower started to develop an oil leak on the rocker cover. This is an OHV 6hp briggs vertical for a Toro walk behind mower. This design is with a die cast rocker cover, then an gasket, than a rocker plate (where the studs holding the rockers are), a gasket (cylinder head style matter) and then the head. This is a 650 Intek I think, not sure with the Toro branding (190cc, and I think this head design is the same for a lot of 120000 and others - pictures below).

Last year, I replaced the rocker cover gasket and the rocker plate gasket, and the mower is still leaking (a bit less, but still a major leak). This morning we decided to disassemble again to analyze. The rocker gasket has the mark (there is an edge in the rocker cover casting) all around in it, looks like it is sealing.
The rocker plate gasket look in good shape, not crushed, but perhaps not sealing in a bottom corner. Was tightened by hand perhaps it was too low torque. Note we bent back the rocker plate last year to make it flat again, when tightening the bolts too much it can curve it.

So now I have a torque wrench, a decided to clean all surfaces, check for flatness (all looks really nice) and torque it to 10Nm for both (as it is in manual for OHV engines).
The result was even worst, as this looks way too much and crushed the gaskets :frown:

I use only brand new briggs gasket and now I have to buy them again. What can I do ? Anyone has a better idea than trying to reasselbe all again for the 3rd time, but now I think I will apply 5-7Nm instead of 10 ? Start to be a bit frustrating and tricky to have this engine oil tight (but it was for 15 years so it should be doable !)

Thanks for any advice

 

[Russ2251]

Had the same issue couple years ago.
Turned out to be a blown head gasket.

 

[Mkala]

Thanks for your quick answer ! :thumbsup:

Forgot to mention, I think of this too, last year, after I discovered it was leaking again. But even if the space with the deck is low, when the mower is raised, I can see from the exhaust side and looks really it's coming from the front. The head is a few centimeter behind, and after a good cleaning it remain dry. So not 100% percent sure, but a least 95%. Or a particular phenomena make it looks like it's the rocker cover gasket even if it's the head gasket ?

 

[Russ2251]

I changed the rocker cover even though it looked OK.
Still leaked.
A friend suggested it could be the head gasket.
I changed it and...voila!!! No more leaks.
I do not know for sure if this the same issue you are having, but definitely check it out.

 

[Mkala]

This could be the culprit too. But I cleaned oil the oil, and was able to see it's come more from the front than the back where the head gasket is.

Ordered both new gasket (rocker plate gaskets and rocker cover) and this time torqued all to 5Nm (even if Die Cast rocker cover is spec for 10Nm - stamped one are 5Nm). After 20mn no leak ! Hope this continue
Added some thread lock to the rocker studs, so they are sealed (and no risk they come loose)

This design is not the best, you torque a part of rocker plate gasket when screwing the plate, and the rest when tightening the rocker cover. However, from factory it was 15 years without leaks - so it's ok - hope I can be as good
On the newer 190CC engines (I have a 850 IC, this was a 650), the rocker studs screw into the head. This is more sturdy, and allow to attach the rocker plate and his gasket to the head. Then you put the rocker gasket and rocker cover, and with 4 screw you tighten all in the same time. Hope this work better, but looks an improvement to me.

See you