07 burgman 400
Hi, engine running, unscrew oil filler cap
Wow, so much presure blasting out
Bike been lacking power lately
Is my head gasket blown on the cam chain side
Any help apreciated

Have you tried a compression test? has it been standing a long time if so it could be stuck
rings.

I use it every day, I dont have a compresion tester
Would be helpfull if someone could undo their oil filler cap whilst engine is running and see if they also have big force blowing from the hole
It,s easy and clean, doesent throw any oil at you

Don't have one to test on but I would not jump to the head gasket before
having a think about it a bit more, how many miles as it got on the clock

23,000
Been at it all day , pulled rocker cover checked clearances just in case nil, holding a valve open
All in spec no prob their.
No smoke or oil consumption
Not exesively noisey , just power is down and exesive crank case presure

In a car, the test for a head gasket was mayonnaise in the oil filler cap. Does that apply to a water-cooled bike?

Wile I know it wont affect the crankcase pressure have you looked at the air filter
the Burger is good at clogging air filters.

23.000 is nothing to these engines.


Rayb
OP thinks it has blown between cylinder and cam chain tunnel so it wont allow water oil contamination
but could pressurize the crankcase, could be right but it is a rare thing to happen.

I don't think its the head gasket, every time the piston is on the power stroke, virtually the same force is pushed into the crankcases, but there is more volume to absorb it. You need to check the venting system of the crankcase, the breather pipes these days don't vent to the air but are recycled via air filter and/or inlet tract.
I had a BMW which had a wrong size breather pipe (a small diameter servo brake pipe wrongly used), running the bike over 3000rpm would blow the rear main bearing seal. It took 3 engine rebuilds to sort that one out by the shop.
Back to your problem, make sure the pipes are not kinked and inside the air box is clear and not blocked with oil. The air box usually has a drain pipe with a bung in it. That needs removing each service or when you see oil in the clear pipe. worth a look, hope it helps.

Thank,s air box is clean
I can hear a sound like exhaust blowing slightly but can,t feel a leak on the system

Possible the noise you are hearing is the head gasket it just seems so unlikely unless
something else has happened to the bike overheating or the like.