With regard to the different styles of sub-trans shifter knobs:
I think this bulletin has the beginnings of an explanation:
http://www.kb0nly.info/ATC/index.php...er+Bracket.pdf
What the bulletin describes is a change to the frame mid-production, specifically to the mounting boss location for the fender mounting screw closest to the footpegs.
A few years ago, I purchased replacement fenders for my 200ES and they bolted up fine, but just didn't line up at that location. I found this bulletin and ordered the brackets which fixed the problem. It appears that the fenders changed along with the frames.
The point of all this is that on my machine, I have the 4-leaf clover style of shifter knob and it hits the fender when trying to shift to reverse. I can't lock the knob into the reverse position due to the interference with the fender (but I can hold it with my hand and it works).
I think the smooth shifter knob is smaller in diameter in order to clear the fenders when shifting to reverse on the machines with this unique frame.
...this is my theory anyway.
Can you post up the VIN to see if it is in the VIN range called out in the bulletin? The bulletin says this affects serial numbers 319300 through 381603.
- Frank
1984 200ES Big Red
1985 350X (x2)
1986 350X
1986 250SX
1984 Auto-X
1984 ATC70
1985 ATC70