I had the same problem with my 1610. This is known as "Slobbering" and I was able to rectify the problem, by changing the exhaust to a short forward pointing type instead of the vertical type.
This may be of interest https://forums.yesterdaystractors.com/threads/slobbering.926289/
Great satisfaction in mowing tall grass and weeds. Only problem I have when mowing tall nettles, grass and thistles in the UK is the radiator gets blocked with grass seed and thistle down making the tractor run hot. I have to stop and blow the radiator out with the airline.