Even doubled up, it is more than 1 link longer than the new one. That means it is more than 2.5 links' stretch, which is a lot! The tensioner was far enough in that the oil seal was loose around the shaft, so it always made the engine oily behind the cylinders. I had to wash it there almost every month to keep things clean.
That is a lot, that would mean a bunch of pin wear and would have some effect on valve timing. I'll be surprised if mine has elongated that much, but I have no way of knowing until I look at it. The tensioner isn't in as far as you've described yours, though. I am debating with myself about pulling the motor at 150K to have a look at the valve train. That is still 6500 miles away, a little over a year at current mileage accumulation. I'll probably do it. I haven't been in there since 2002 at 82,000 miles when I did the cam tower seals. That was 61,000 miles ago. I've seen many V8 and Toyota 22R timing chains with a lot of elongation at 130-150K. I've done a few 22R chain and gear set replacements, both double row and later single row chains, and they get pretty floppy.
Out of curiosity, how were the tappet clearances holding on yours before you tore it down?
Once it wore through the hardening on the ends, it became more frequent to find them loose. This started happening around 100k miles or so. You can see in the pix of the valves earlier: there is a little circular area in the center of the tip that has become dished and shiny. I'd estimate it to be about .002" deep on the worst ones.
I'm having the longer K1-style exhaust valve guides installed again this time around. They are 50% longer than the 'regular' ones, and I am not going to run a high-lift cam, so they will fit well and will cool the valves much better. I think that, plus the stellite valves (if my OEM ones survive their refacing/hardening) should put me back on the pavement for another 100k.
I looked at the seal in the tensioner: it is cracked, likely due to age. I suppose that's where much of the leak happened?
Mine's cam sprocket is the old 'holey' type from the K0-K1 era. These were hardened: the solid style were not, starting around 3/72 builds of the K2. The "F" bikes in 1975 got the 'holey' ones again, and were also hard. This does a lot for their life. The only real shortcoming in the later engines in this area was/is the shorter slipper tensioner where the tops are "cut off" in appearance. Today, more often than not, when you order a slipper tensioner you get the 'short' one because it will fit all the engines: but if you can find a long one, it lasts almost twice as long. In the post-1975 head there is a casting edge in the way of using the longer ones: you have to file it away to slide the new tensioner in. In the F2/3 heads, it will not fit at all, though, because the tunnel is shorter on the front side: there, you must use the short slipper.
The cam chains with the "410" middle number have now superceded the older "283" number (which came from the CB350 twin engines). That's not a bad thing: the pins in the "410" chain are slightly larger diameter, which bodes well for future [lack of] wear!
