Unspeakable timing chain

[WulfgartheBlack]

OK I just got the beast ready for Spring - new sprockets and chain, oil, filter, clutch cable, etc. Even invented a retainer for the fuel snorkel. Gas into the tank, tickle the carbs and kick it three or four times. She began to catch a couple of times, started to run - then suddenly NO compression! The pistons are working - I can hear their sound in the exhaust. Opened the valve adjust port and peeked in. NO timer chain!
Well that sucks, but wait! That's not the first time for this particular problem. The bike before -also an '81 and now my parts bike - did the same thing. I was riding it at the time. Pulled away from a stop sign - suddenly NO compression. Peeked in and that timer chain had also parted and dropped down the holes into the bottom of the case.

The first time this happenned I worked out that dragging it to somebody with the skills, etc. and paying him to fix it would cost almost as much as buying a running bike. Plus, I'd have spare parts for almost everything.
So now I've got two copies of the type, fiddled with it for almost four years and worked on most of the design flaws till it's comfortable and [I thought] reliable.

Now the question: Is this a common thing with this engine or did I just stumble over two bad timer chains out of hundreds? I'd rather ride it than work on it or wait for somebody else to fix it - only to have the same thing happen again in a couple of thousand miles

Have any of the rest of you had this happen?

 

[Greasey Fingers]

wow that sucks, ive never heard of that happening before, let alone twice to the same person on different bikes!

 

[226dark]

wow that sucks, ive never heard of that happening before, let alone twice to the same person on different bikes!

Haven't heard that either! Wow is right!! Only way for it to end up in case is for the chain to break (unless there was no camshaft, ha!) Maybe possible with valve cover removed and a very strong magnet pick-up tool to fish it out of there? I would think when you try to start it that it would not turn over so easy if the chain was bunched up down there and binding.
I haven't looked but i didn't think it was even possible to actually see the timing chain from the valve-adjust cover openings. Hence no timing chain.
Suddenly no compression, but also suddenly at same time you didn't hear anything else!
Test the compression, adjust the timing - clean the plugs while your at it, and make sure there is gasoline

 

[226dark]

Ok, so I checked and I could see it. Maybe it would be easier to see and be sure of it while turning the engine. Not sure it would happen but if one of timing chain sprocket bolts came loose or tensioner wasn't doing it's job, or front chain guide missing then chain may have jumped off the sprocket. Can you have a look from all 4 angles and see it at all?

 

[HoughMade]

I have never, ever, heard of this happening. I suspect something else is going on, but you're there, I'm not. I'd try cranking it over with a valve cap off just to check to see if the valves move.

 

[226dark]

Realistically, I would say if you are CERTAIN "no timer chain" (on the sprocket anyway), then valve cover off it will be plain to see. It will have to be done anyway if that is the case.
Somewhere I heard of someone with a damaged cam chain guide, though rare.

 

[drewpy]

don't turn the engine over with no cam chain, the open valves will hit the piston and bend.
you can get timing chains with a soft link which lets you peen over the link a bit like an o ring chain.

personally i'd use the endless chain as that's OEM but it means splitting the crankcases.

never heard of 1 go let alone 2. (till now)

 

[HoughMade]

Let me be more specific, turn the engine over slowly with the kick starter or by hand to see if the valves move at all. Like I said, I'm not there, but something doesn't sound right about this diagnosis. How do you know there is no compression?