Hi all, me again...

every time i turn off the bike and put it on the side stand few drops of coolant come out from the breather on the left side of the engine head

Since i recently discovered that the previous owner had overfilled the engine with 1 litre of oil in excess ( !!!) i'm very scared something could have been seriously damaged, like the head gasket....

any test i can do to find out???
what else could it be??

so i found out it should be a drain from the sparkplug socket, very usefull on enduro bikes that get dirty and wet everywhere...

at this point i'm sure the head gasket is leaking somewhere near there and allows the coolant out...

i checked the oil and it looks ok so hopefully it's just a minor leak...

what involves to replace the head gasket??? simply unbolt the screws, plugs take out the cover, replace gasket and close everything????

Not as simple as that.
First make sure it is coolant, what colour is it .
Replacing the cylinder head gasket is quite an involved procedure and demands some mechanical skills as well as specialised tools ie torque wrench .
Being able to time the valves and replace the cam bearing carriers in their correct seats is vital otherwise you could ruin the head the cam bearing carriers are not interchangeable and have to be replaced in their original positions with great care as the carriers are easily cracked .
The fact you are asking about breather pipes on the engine when in fact you meant the spark plug drain holes suggests you have limited mechanical knowledge .

hi, thanks for your answer

i have a friend car mechanic who would help me in the job..

i'm not sure what this little hole is for, looking on the internet i found out that it could be a drain from the sparkplug hole, but not sure to be honest...

do you know that that hole is meant to be?

i just discovered that i have a small leak from an oring in the thermostat which is right above the head, i'm wondering if riding some liquid could somehow go onto the head, through the sparkplug hole and then spill from that little hole, this could exclude the gasket issue...
in fact, the bike runs prefect, no esitation, no strange smoke, no sign of oil in the coolant and viceversa..

i will replace the oring and see what happens

Making sure the thermostat housing and the connecting hoses are all water tight would be the easiest and cheapest option
The small hole in the side of the cylinder head is indeed a drain hole from the spark plugs.

.

UPDATE

so finally today I found something, and it's not very nice:

in the 1st spark plug well on the left, in the gasket between the valve cover head and the head i saw few drops of "milkshake", damn!!!!!!

so definetly the valve cover gasket is gone, and somewhere the oil is mixing with coolant
i will open it to see what's going on inside, what i don't get is that the coolant looks fine as well as the oil (well, so far).....

took the bike this morning, coolant is fine as well as oil...

still leaking from sparkplug drain hole, no sign of oil/coolant mix near the gasket,
searching the web i read about 2 more possible causes (not cb400sf related but general engines):

1:freeze plugs that can pop out or brake and allow coolant up to the valves and then spill from the bad valve cover gasket and could mix with oil (read this on a suzuki gsxr forum)

2: intake manifold failure that would allow coolant in the spark plug well (read this on some cars forum)

could not find anything similar in the cb400sf manual though...

PLEASE HELP!!!!!

...last thing:

I noticed some residue of leak between the head and the coolant hose that goes from the left back of the head to the thermostat..

now there is a o'ring inside, could this o'ring cause th coolant to spill up to the valves when in pressure???

any suggestions??