$tuck exhaust valve

[IruaL]

Lost the right cylinder today. Found this:



How much clearance is there for the piston and open valve? Not that much i'm guessing.
I didn't hear a bang when it happened.

Could there be another reason for the valve to be open other than meeting the piston and bending.

[sgoodwin]

Could be seized in the guide, but it looks like there's plenty of oil. Can't say I've seen this in boxers with rev limiters. Could be the cam chain tensioner took a dump & chain jumped teeth. Any idea yet what happened?

[IruaL]

No idea. I will look into it over the weekend. Should i bother trying to get it unstuck somehow or just take the head off and have a look?

It happened when i accelerated to about 7000rpm. I cant remember if it was before or after closing the throttle for the gear change. I didn't hit the limiter and I didn't downshift accidentally.

Sucks, only had the bike for a few months.

[sgoodwin]

Remove the head otherwise you're just guessing.

[tjs]

R11S or R12S ?

[brentw1]

sadly usually bent valve, check the cam timing.
unless you ingested a bold or other foreign object that is jamming the valve open,
but probably bent now, you can pull the port and look at the back of the valve
this is not a clearance motor, check the other side as well, cam chains etc.
tensioners,

[IruaL]

Thanks for thinking along guys. I have to pull the head sometime later, have to go on a work trip.
Measured that the valve is about 5mm open - is that as far as they go or half way open?

Originally Posted by tjs

R11S or R12S ?

At least it happened close to home and the season is over soon too.

[tjs]

Nice Bike. Did you remove top spark plug? If so was the electrode still there? If not, the valve broke.

[IruaL]

Broken valve bits getting between the electrode and piston?
The spark plug was fine.

[tjs]

Good. probably just bent. This is what spark plug with boken electrode looks like.

[DPG]

Maybe a bent pushrod? I've had hexed valves go twice now and there's no way you could miss the racket a valve/piston interface moment makes.

Like SGoodwin says, you got to open it up and see. If the motr will still turn over maybe do a compression test?

[sgoodwin]

I wouldn't turn anything not knowing what happened, never know what extra damage you can cause.

[BadToTheBown]

Really doubt it is stuck in the guide, probably a bent valve and I'm not yet sure why but it is usually the right piston that catches the valves first (ask me how I know this). Find TDC, lock it into position (BMW makes a little plastic insert that goes where the starter is to lock the flywheel on the R11xx engines, maybe for these too) and pull the head. With any luck the valve seat isn't screwed, that's not so easy to fix. Best of luck.

[GUS]

Hi
As others have said, remove head and have a look. Do not try and turn the engine over.
RHS failures are not uncommon. Exhaust valves usually the culprit.
Here are my failed valves. The other 2 valve heads exited through the exhaust along with the piston which also tried to escape through the top of the crankcase.



Here is whats left of the engine. All scrap!!!


Goodluck with the rebuild.

Gus

[Psychopath]

Wow. You guys are making this sound like it's somewhat common in hex heads. If that's the case maybe I will stop considering trading up from my R11.

[GUS]

With the amount of hex head 1200 motors made and the amount of failures. It's not really a big concern. Lots of factors contribute to failures, over revved(down shifting), too lean mixture(burns valves), , incorrect valve clearance /end float, engines running hot etc etc.
Mine went in a race in high temps whilst stretching the motor a bit too far.
Gus

[BadToTheBown]

Yeh, sorry that's how it turned out. Shame but I've been there more than once...

[sgoodwin]

So is it apart yet? We need to see some damage!

[IruaL]

Enjoy.
Imgur

[tjs]

Damn! Minimal Damage.