What happens when I screw up my cam chain tensioner?

[jonathan_whitwell]

Oh, what have I done! I may have destroyed two perfectly good GS motorcycles due to my ignorance of how the automatic cam chain tensioner is supposed to work. Here's exactly what I did: I loosened the lock nut and screw (on the left side of the tensioner), turned the engine forward slowly until the tensioner was as taunt as possible, and then tightened the screw ALL THE WAY DOWN and locked it there with the locknut. AHHHH! WRONG!!! I thought that was what I was supposed to do until today when I read bwringers guide to rebuilding tensioners.
So the first one was a 81 GS450E, good little bike. I adjusted the tensioner like I described before, and it worked fine for a few months. Then I went on a long trip down the highway, it slowly started making a really loud slapping noise from the valve train, which eventually got really bad and I lost most power and had to pull over to the left side of the road. I went to get a pickup truck, but by the time I got back the California Highway Patrol had towed my bike (I was gone for like 1.5 hours!). I thought that the exhaust valves were all burned up and bent because that bike had the shims and I never got around to adjusting them, even though I knew it needed it. I didn't think my towing bill was worth a destroyed motorcycle, so I let the tow company keep it.
Next bike was an 82 GS750 (I think it was e too, but not sure). One of the first things I did when I got it was adjust the valves (I did that right) and adjust the cam chain tensioner (I did that the wrong way as described above). This morning I again had to make a particularly long trip on a few highways, and when I was about 10 miles from home I heard the cam chain getting really loose (it sounded like the cam chain to me). I tried to limp it home, but it didn't make it. The sound was really loud, and I had very little power. Now I'm waiting for my friend with a pickup truck to get off work so I can get my bike off the side of the road and into the garage.
I now know how to properly inspect/set up the automatic cam chain tensioner. My question is this:
What did this improper maintenance do to my bike? Is it bad enough that I should go find another $500 GS and part this out on e-bay? I know the cam chain isn't broke, because it ran even after I pulled it over. I'm hoping (and praying [-o<) that I can just put a new tensioner on it, and it'll be fine.
Thanks.
-Jon

[jonathan_whitwell]

forgot to add

The gs750 has 66,000 miles on it. It's been running with the cam chain tensioner locked for a couple months now. It also happened to break down after I took my girlfriend to work (that's what the exceptional long drive on the highway was for). This was the first time the bike had a passenger on it. Don't know if any of that makes a difference, but now you know.

[bwringer]

Unlock the cam chain tensioner, set it correctly and see what happens.You might also want to pull the valve cover and verify that the cams are still timed correctly (see your friendly neighborhood shop manual -- it's not difficult, but you must have the specific information for your model).

Four out of the six or seven GS850 engines I've had my mitts on have arrived with locked cam chain tensioners. I don't know why, exactly, but apparently the lockscrew and locknut were just too tempting for many past mechanics. No ill effects so far in my limited experience -- even if the cam chain gets fairly noisy, it's rare that it actually gets loose enough to skip time.

It would also be a good idea to check for excess wear on the plastic surfaces of the tensioner blades and cam chain guides.

[t3rmin]

Yeah I'd check that cam timing. After putting a new cam chain on last weekend and messing with the tensioner and such, I'm reminded how easy it is for a cam to slip a tooth if there's not adequate tension.