I sold my '90 a few weeks ago. I had never had any oil leak of any type. The new owner says it is leaking while riding but not when parked. Leak seems to come from above the shifter. A few days prior to selling, I found a rectangular rubber cap thing ( hey I'm NOT mechanical) maybe 2 x 3 in. near the front left peg/shifter area on the ground. I assume it is from the bike. I've looked at schematics but don't see it. Any ideas may be helpful. Thanks.