View Single Post
Old 11-03-2012, 06:58 PM   #21
itsatdm
Beastly Adventurer
 
itsatdm's Avatar
 
Joined: Jun 2004
Location: Nor Ca.
Oddometer: 4,732
What you are looking at on the end of the exhaust cam is the remnants of your automatic compression release mechanism. It consist of 2 weights pivoted on one end connected by a coil spring that keep 1 exhaust valve partially open at cranking speeds.

I think the spring broke or unhooked allowing one of the weights to open enough to hit the head and leverage the exhaust cam up with enough force to pull the cam cap bolt out the head. There are more parts to it some where.

That might have allowed the cam chain to either come off or slip enough to cause the the valves to contact the piston and bend. In any event, the fact that the starter can't turn over the engine is probably because the bike is out of time and the valves are hitting the piston. How that occured merely cranking the bike is a mystery to me. If you hand turned the engine clock wise, it could have allowed the chain tensioner to back off.

You might be able to fix it, if the cams or bearings did not get scored but probably be cheaper to find another head complete with cams. You will need more disassembly to determine what else is damaged.
__________________
BMW Motorrad USA customer service: "We make superior motorcycles and continue to improve them."

itsatdm screwed with this post 11-07-2012 at 02:09 PM
itsatdm is online now   Reply With Quote