I guess then as @Rob G suggests, what stops you turning the whole rod?It's not, they are usually all the same way around. Thats why it seems odd to me.
No, I was measuring with a micrometer
Absolutely 100% it's the original part
Small end is fine, checked that.
Checked that too, it's normal. It's defo the big end as it turns fine when the big end is finger tight and only goes stiff when I torque it.
It was a running engine when I stripped it, and I set it to TDC to disassemble and I f it was this stiff i'm sure I would have noticed it.
Thanks for the input though. It HAS to be something to do with the rod/cap. I guess i'll have to pull it out again and take it to a machine shop to check the big end for roundness in case it was bent, damaged or something when the pistons were fitted.
Otherwise I'd be inclined to agree, if the crank is known to be good then the next thing would be measuring the inside of the rod for roundness.
Nothings ever easy and it sounds like you've got a good handle on it