Heh Cal,
The crank pin is a big weak point on these engines!!! You say, 'The rod movement gets very sticky or tight feeling'. This should not be the case, if I was you I'd be on the phone to uncle Bob asking him for a big end repair kit which includes the crank pin, bearing and thrust washers. Get the engine out and have a look, the sticky tight feeling is definitely enough for alarm bells.
The development of these engines goes back a long way with revs and power increasing gradually and as far as I know the crank pin only got beefed up on the GFR. In my experience on the Apache and Crono series engines the big end bearing starts to pick up on the crank pin at quite low mileages. By the time the big end starts knocking microscopic bits of the crank pin have been thrown around the engine accelerating wear and causing scoring. That's what happened on my Apache and I've had it from new and always run in on quality two stroke oil. It started to knock at below 12000 miles. You'll probably be able a reuse the crank rod but I chose to renew mine due to heat discoloration around the big end. Having said that I don't think this problem would cause the discoloration of the crank that I see in your picture.
I've just re-built two other engines (one Crono and one Apache) and on both of them the crank pins were picking up!! If I knew how to upload pictures I'd stick them up for you to see the horrors that could be lurking in your big end.
Had my cranks rebuilt by Piston Broke in Bristol.
Good luck,
Leigh
