I have an '85 B8200HST that I've owned for most of it's life. Over the past 6 months or so the RPMs have begun to fluctuate wildly, even under the lightest of stresses. I rebuilt it about 4 years ago and it has always started without trouble and easily revved to normal RPMs as called for. No smoke, no noises, just no power, and it seems to be getting worse. Any insight would be appreciated. Thank you for reading.