I've been living with this issue for lack of time to troubleshoot for months. I have some time now to hopefully get it resolved so I am seeking the wisdom of the group. I am getting a pronounced bucking, almost a jackhammer feeling particularly at 5k and to a lesser degree at 7k. This ONLY occurs if I am coming off throttle and try to cruise at those rpms. If I am just revving up through the RPM range, I pass through 5 and 7 with absolutely no issue. It's only when holding steady throttle at 5 or 7, particularly if I am coming down to either from higher rpm. I'm not close to an expert, but this does not seem like a jetting issue per se to me, partly because I did not touch the jetting prior to this starting to happen and it revs up fine throughout the rev range, with none of that bogging, strangled feel that one feels when jetting is way off. Also, the plug color is fine. The only possible diagnostic clue I have is that it seems to me that this started after I had run a tank of av gas that had been in the tank for about 3-4 weeks before running. I would really appreciate some help. I can live with it as is, but I would rather get it resolved if possible.

Jim
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-Jim
'93 MC21