Vista Dsl flutters at top speed.

Hey MM guys. That freshly overhauled 504 on one of our Vista's runs great but we put it to work on a grain vac and it is a fair load for it but it can run it fine. The only thing is it sounds rough at the top end from about 1600 and up. The exhaust doesn't sound crisp and clear, instead it almost sounds like the governor is making it flutter. Is this something that can happen with the Rosa Master system? It sounds great as you push the throttle until it catches up to itself then has that flutter sound. I know many years ago we used to have a G-VI that sounded that way all the time at full throttle and a mechanic that we had out said it was the governor doing that. He tried to put in some waver washers to stop that sound but I don't remember it helping. Always sounded like a little miss at the top. This Vista seems to make that same sound only louder and it does smoke quite a bit and it seems to come out in surges instead of an even flow. On this one we did NOT have the pump checked out nor the injectors since it seemed to run pretty smooth before as I remembered. It does pop and sputter a little more than I would like when it's cold too if that info helps find a cause. Any ideas will be appreciated. Thanks.

Make sure engine is not running a faster high idle speed than it should be, that can make the miss sound too. Next would be timing, if set on the retarded side will cause the same sound. If both check out I would suspect the retainer ring is breaking apart then. Just repaired a Case 580 pump for the same trouble.

It may be worthwhile to check the pump drive gear train if the tractor is high hours, 7000 or more. We had excessive wear in one location on the drive intermediate gear, loaded heavily ran pretty good at high idle light load allowed the backlash to come into play=diddle