cmichael,
My 86K100RS had exactly the same issue with broken gears.
I took my instrument cluster to Hamp's Speedometer in Atlanta this past weekend & he quickly pointed out the 3 failed gears. He said it was a common failure in this vintage BMW bikes. He had one of the gears in stock & said he would have to order the other two. He said he would put it back together & bench test. I expect to receive it back in the mail for less than $200.
You did well buying the gears & replacing them yourself. ~HCurrier