Vintage Dirt Bike Q & A

I have a 1981 CR250R with a 1980 CR250R motor, I didn't chop the thing, It's the way I found it. I bought it from an ad I saw on a local craigs list post. It was listed as an 81 CR250R missing some pieces ie: the left side engine cover, the kicker shaft, the kicker, the shifter, and all the cover screws. $150.00 When I got there I saw the air cooled motor and was puzzled and I figured someone must have swapped out the 81 motor, though I can't imagine why. Was the 81 mill a pig? did it have poor performance? anyway I'm having some issues with the conversion like the kicker doesnt have enough stroke because it hits the head of the upper bolt on the left footpeg mount. Another problem is the pipe I dont know if its off the 80 or the 81, maybe you guys could help IDing it any telltale differences you could point out? The tank, off the 80 (plastic) had to be spaced up to clear the top of the pipe and I can't get the 81 side covers on because the pipe sticks out too far. It had a clamp on foam air filter which was falling off so I bought a used 81 airbox and put it on, It must've had a intake off an 81 because the angle was perfect to line up with the intake boot on the air filter box. I'm an Industrial maintainance mechanic / machinist and I have a full machine shop and MIG TIG and gas welders and plasma cutter so fabbing up parts is no problem. I already made a new chain guide and and I bought a folding shifter for an 81 which I plan to cut, re-shape and re-weld for the bike. I also got all the missing parts for the left side and put it all back together and got it running. I think I like the idea of the prolink frame and the 80 air cooled rocket motor by the way the motor was not red maybe it was a replacement? any ideas? seems to be tight and healthy I plan to go over the whole thing clean up some the quirky s__it and make it look and work more like it was that way from day one instead of a Frankensteins monster