I finally got my 69 running and started heading out into the field and the master link popped and was lost. I measured the pins and while it looks to be 1/2" pitch it lengthens as one measures a longer length....but as original as this chain looks (6500 miles on bike) it could very well be stretched. I have a 420 chain that looks too skinny, about 1/4" roller width (side to side, not diameter). This chain looks closer to 5/16"....though I'm sure it's really a mm measurement. I can't find any documentation anywhere telling me what the stock chain should be.

20 pins is 10.25", and going around the rear sprocket it sits dead perfect the whole way around. That's like .5125" pitch. Teeth on rear sprocket look good.

Can I do a conversion to something else?

428 it is. No54
www.babbittsonline.com/oemparts/a/yam/50...9bc7842a0/rear-wheel

Sheesh, ya know I looked at the microfische first. I never heard of a 428 size chain so I read right over that number.....

...had a 428 Cobra Jet once....

428 chains super cheap!