f650 engine broke

[SteveSardone]

I'm starting to tear apart my sons '01 f650 engine with 50k miles. He isn't the most meticulous about maintenance but he changes the oil regularly and checks the coolant. He had the valves adjusted by an old bmw guy in chattanooga who has a garage full of old beemers. We assume he knew what he was doing. It froze up on him about a week ago. I pulled it on Tuesday and today I pulled the head off and this is what I saw. pics attached. Any of you mechanics have a probable cause for valves breaking?

 

thanks for any insight,

 

Steve

[smiller]

Ouch.

 

How many miles between the valve adjustment and the failure? I'm not sure how a simple valve misadjustment could cause that unless the valve was adjusted extremely tight causing it to burn, but even if so usually the edge burns first and in that case I would expect that the loss of compression would be immediately evident. I suppose that if it wasn't and the valve was left to burn for an extended period of time (and the seat does look rather badly erroded, implying that this could have been the case) then the valve head could separate, but not sure how likely it would be for all the elements of that kind of scenario to come together. Could just be an unrelated failure, don't know how you'd ever know for sure.

[SteveSardone]

Seth,

 

I'm not sure but I would have to guess over 5000 since adjustment. He had just come back from a 2000 mile trip to chattanooga on the 650. I'm not trying to blame the guy who did the adjustment-just trying to lay out what I know. Thanks for your input. My son now has to decide if we try to rebuild it, buy a used engine or just part it out. I was just out in the garage looking it over again and I saw a crack in the cylinder-I guess a rebuild would include a new head, cylinder, and piston at the minimum.

 

Steve

[smiller]

Yeah, I was thinking that the cylinder couldn't be looking to spiffy either.

 

The erroded seat is interesting. I doubt that damage happened after the valve let go since the engine would have stopped immediately, looks more like it happened over time and the valve head had been cooking for a while, explaining why the stem failed. Could have been a (very) bad adjustment, a chunk of carbon in the wrong place, or just age (although 50k miles isn't all that much.)

 

I can't advise as to the most economical way to go at a repair, perhaps someone with more F650 experience could comment.

[HairyCannonball]

If the valve head came off at high rpm it could have pounded the seat like that before the engine came to a stop. If it was adjusted so bad that erosion caused the seat damage it would have been running like crap ever since the adjustment. It's not unheard of for valve heads to come off. I think it was just an unfortunate valve failure unrelated to the adjustment. JMO

[ShovelStrokeEd]

Looks like over rev to me coupled with valve to piston contact. Might be that the valve springs have lost tension over time and he encountered valve float sooner than the factory rev limiter could protect the engine.

At high revs, the type of damage you see here can happen in seconds. DAMHIK!

[StuGotz]

I think Ed might be on to this one.

 

Same here, me thinks the valve gear couldn't keep up. What's the stem look like, or have you disassembled yet?

 

MB>

[SteveSardone]

thanks for all the insights. I haven't further disassembled it yet-don't really know how but I guess I will figure it out. Any trick to getting the valves out? So to cause the over rev issue it would have to be weak springs or the limiter didn't work?

 

thanks,

 

Steve

[ShovelStrokeEd]

Steve,

Just buy a new head, that one should become a garage trophy. You are probably going to need a new cylinder and piston as well and it really wouldn't be a bad idea to have the connecting rod checked for straightness and twist.

[SteveSardone]

My son decided to part it out. I already have most of the frame stripped. I posted in the classifieds at the chain gang. thanks for all your help.

 

Steve

[70marlin]

I’m not sure what the composite is for these beemer’s F valves are? I’ve seen that existent of damage before. The RFS (Race four stroke)motors that have titanium valves will tulip and snap off the head if they’ve been run hard and past there service limits. Also there’ve been a few (Japanese) company’s that have had bad valve that just seem to like to snap off. Good luck with your repairs.