Blown head gasket?

[gav]

What are the symptoms of a blown head gasket in a air cooled engine?
I've recently bought an old GPz550 race bike and first meeting was yesterday.
Didnt go that well as it appeared to dump oil into the airbox and eventually over the rear end of the bike, including the rear wheel. After one heck of a rear end slide ended up parking it against the tyre wall. Oil was everywhere and dripping from the motor. I thought it had blown something serious, but back in the pits it was decided it was overfilled with oil. It was also suggested that the head gasket may be blown, how best to check?
Still seems to run fine, no excess smoke etc? Could the engine oil get contaminated with petrol causing it too appear the oil was overfilled? Have drained the oil and seemed very thin, but dont know how old it is?
Anyway of checking before I replace oil and filter?

[mioraet]

I've had petrol end up in the oil on a DR 350 I had due to a leaking needle valve it just kept letting petrol leak thru from the float chamber and of course it dribbled through the inlet tract and past the rings. I must have ended up with a couple of litres of petrol in the cases (dry sump), So I guess thats a plausible reason. If it's not smoking or leaking oil from around the head I would doubt it has blown a gasket.

[FJRider]

You would notice (usually) oil leaking out the head gasket, or stains showing where. Air cooled bikes have oil channels in the cylinders to the head. If the gasket goes, it has to go inwards(lots of smoke) or outwards(oil stained engine casings).
A compression test will tell lots... more likely, rings and valves...or cracked head.

[YellowDog]

Mate, it sounds like your poor bike is trying to survive by puking all the crap out that ain't where it should be. Probably not a head gasket. Suggest you drain out the oil and start again at the right levels.

Good luck.

[themechanics]

i think id go with yellow dogs plan,get ya levels right go from there gd luk

[Ixion]

,,, Have drained the oil and seemed very thin, but dont know how old it is?
Anyway of checking before I replace oil and filter?

Would not basic prudence suggest replacing oil and filter before a race meeting, most especially on a machine of unknown provenance ?

[gav]

Would not basic prudence suggest replacing oil and filter before a race meeting, most especially on a machine of unknown provenance ?

Probably, but didnt say the bike was unknown just unsure when the last change was. Turns out the fuel tap has been leaking, with fuel leaking into the airbox and from there into the crankcase.

[Ixion]

In which case you may wish to subject your big end bearings to intense scutiny.

[YellowDog]

In which case you may wish to subject your big end bearings to intense scutiny.

The prime reason the last guy sold it is now becoming quite clear.

[gav]

The prime reason the last guy sold it is now becoming quite clear.

Really? He fall off it and is/was moving to Aus?
Nah its all good, don't think it ran long enough to cause too much damage.
Considering what I paid for it, its not worth stripping motor, if it shits itself, I'll just get another motor.

[YellowDog]

Good attitude Gav.

Hope it all works out well for you.