Hey Claude

[ME 109]

Here's one of mine you didn't see. Timing chain link clip wore out and fell off.
I'd like to know how on the side of the road with Charlie, I was able to turn the engine over for a couple of bursts with the starter, and then turn the engine over with the wheel, plugs out. I could here the chain rattling!
Not a mark on a piston crown.
It looks like a busted cuckoo clock.

[gspd]

ROTFLMAO !!!!!!
This is a day of 'firsts' for me
Did you ever find the clip?
Was it actually worn out? or did it just come off?
You do know they have to be installed with the opening in a specific direction and that the square edge (if applicable) has to be outwards, don't you?
At what RPM did this happen?

[gspd]

I don't have an open engine around at the moment, but I was wondering how that tensioner spring could pop out like that.

[ME 109]

I found the clip and studying with a magnifying glass showed it just worn out. I do put the clip on correctly.
Fortunately this happened at about 2,000 rpm. Lucky!
The tensioner...... there is something with that. The front bearing carrier was swapped in with another crank, after the oil filter bypass spring broke and eventually got to the rear crank main and killed it.

I did notice last time I was in the timing cover after the clip fell off, that the tensioner piston would not fully depress into the bearing carrier. I became a little suspicious after trying with the original bearing carrier and piston and found the piston can fully depress into the carrier. This was after I'd buttoned everything up.
I've been wanting to get back in there and see exactly what's going on with the piston. I'm wondering if there is somehow a longer piston in there. Basically the piston bottoms in the carrier with x amount of piston still sitting proud of the carrier. Whatever is going on allowed the bunched chain to push on the piston and push the retaining plug out.

Notice the pressure relief valve? The chain bent it. Luckily I decided not to use it because I found the piston seized in the closed position due to the housing being bent.

[gspd]

A lot of seemingly knowledgeable people I've met are not aware that those retaining clips have a front and a back side and that the opening faces away from the direction of travel.

For safety, most racetracks insist on only riveted links for drive chains.

[gspd]

How many jkm*'s were on this link when it let go?

* 1 jkm (jeffkilometer) = 1.5 km

[ME 109]

Not sure on k’s. Maybe 35-45k
Three years of 8,000+ anyhoo.

[Wobbly]

The cam chain tension blade spring might have gotten loose first. Then the the extra chain flapping induced the master link out of position.

I'm no BMW expert, but I don't remember seeing a spring well that goes all the way through like yours does. I'm fairly sure my bike has a blind hole for the cam tensioner blade plunger and spring to sit in.

[gspd]

I was thinking the same thing as you, Wobbly.
I checked on an old engine; the bottom of the spring hole has a steel plug, sort of like a frost plug in an car engine block, that looks like it was pressed and peened into the hole in the alloy casting. Maybe this plug came out, caused excess play in the chain, and then the link let go. That could explain why Jeff was able to crank the engine over a few rotations before it jammed.

[ME 109]

Didn't notice any timing chain noise prior to the clip falling off.
I can see where the clip was worn by the link pin. I did try to analyse what happened by looking at wear marks on all components and although the wear is apparent, I couldn't come up with an answer as to what forces caused the particular wear.
Strange dynamics may exist at high rpm, but then not many people report a link coming off.