Could be a lot of things. Maybe related to the recent work you did, maybe not.
I'm not suggesting anything, just mentioning this because your description basically fits the buzzing sound that can come from a defective starter clutch. One day it will start to buzz/vibrate and it's generally much more noticable after you've revved it and the rpm's are coming down under approx' 2,500 rpm's. That's what mine did. Seems funny but when I first heard it I found that moderately pressing against the stick-on case emblem quieted the sound. I actually thought it may be the emblem at first but that proved wrong.
After replacing the starter clutch I never did see any sign of why it buzzed/vibrated. The rotor wasn't loose, no odd wear marks on the shaft. Two of the 3 springs in the starter clutch were shot though. The rollers didn't allow a good grip either. Lots of slipping wear on the inside of the primary gear.
Backing up a bit, it's my opinion that a bad starter clutch would give you fair warning though before any buzzing sounds started coming. Generally, you hear a loud "CLACK" at the first stage of starter clutch failure. After time, it gets worse and gets to the point where it clacks everytime you start up, especially when cold.
If yours has done any of that, it may be the starter clutch. If no previous sounds have been noticed, then it could still be the starter clutch but it's less likely.
I'm not suggesting anything, just mentioning this because your description basically fits the buzzing sound that can come from a defective starter clutch. One day it will start to buzz/vibrate and it's generally much more noticable after you've revved it and the rpm's are coming down under approx' 2,500 rpm's. That's what mine did. Seems funny but when I first heard it I found that moderately pressing against the stick-on case emblem quieted the sound. I actually thought it may be the emblem at first but that proved wrong.
After replacing the starter clutch I never did see any sign of why it buzzed/vibrated. The rotor wasn't loose, no odd wear marks on the shaft. Two of the 3 springs in the starter clutch were shot though. The rollers didn't allow a good grip either. Lots of slipping wear on the inside of the primary gear.
Backing up a bit, it's my opinion that a bad starter clutch would give you fair warning though before any buzzing sounds started coming. Generally, you hear a loud "CLACK" at the first stage of starter clutch failure. After time, it gets worse and gets to the point where it clacks everytime you start up, especially when cold.
If yours has done any of that, it may be the starter clutch. If no previous sounds have been noticed, then it could still be the starter clutch but it's less likely.