CaJo
New member
I have been a long time guest on this site and always found the answers that I have been looking for, so thanks to everyone for your previous help, but this one has me stumped.
I have a John Deere F687 with a 60" 7Iron Deck, 23hp Kohler. For those of you who are not familiar this unit has an electric clutch that engages a PTO shaft which goes to a gearbox running the deck belt. The problem I have is that I get really bad vibration on the shaft and deck when I engage the PTO approximately 4 out of 5 times. About 1 in 5 times when I engage the PTO it is smooth with no vibration. Normally I am going to begin mowing I have to engage the PTO throttle up and if there is vibration throttle down and disengage the PTO and try again. It takes several attempts then it will engage smooth. Occasionally it is smooth in the first attempt.
What has be stumped is if this is a balance issue why would it ever be smooth, wouldn't it always vibrate? The only thing that can change is the place in rotation where the clutch engages which would do something to cancel unbalance or alignment, but I don't see how that can happen.
Things checked thus far:
There is no slop in the PTO shaft or the clutch that I can find, it spins freely and engages solid. The clutch adjustments have all been checked and they are even and in spec for this clutch. There is one counter weight on a pulley coming from the shaft out of the engine, it is positioned from the factory. I did tear this motor apart to repair a leaking rear main seal and was careful to bolt everything back in the same orientation as before. If a shaft was bolted in the wrong orientation I would imagine that it would always vibrate anyway so I don't know how that can be the issue. I bought this unit used with the leaking rear main, so I cannot say if it was vibrating prior to taking it apart but the guy selling it didn't mention anything and I did run it a little bit without issue.
I have replaced the U-joints in the PTO shaft.
The gearbox shafts are solid and have no play.
Blades are balanced and tight spindles are good, belt is tight and in good shape.
The only thing I can think to do next is to take the balance on the pulley and move it in 90 degree increments to check for vibration, the shaft out of the engine could only have been bolted in place in 90 degree shifts so one of them would have to align it again.
Any advice or pointers that anyone can offer at this point is appreciated.
Thanks.
I have a John Deere F687 with a 60" 7Iron Deck, 23hp Kohler. For those of you who are not familiar this unit has an electric clutch that engages a PTO shaft which goes to a gearbox running the deck belt. The problem I have is that I get really bad vibration on the shaft and deck when I engage the PTO approximately 4 out of 5 times. About 1 in 5 times when I engage the PTO it is smooth with no vibration. Normally I am going to begin mowing I have to engage the PTO throttle up and if there is vibration throttle down and disengage the PTO and try again. It takes several attempts then it will engage smooth. Occasionally it is smooth in the first attempt.
What has be stumped is if this is a balance issue why would it ever be smooth, wouldn't it always vibrate? The only thing that can change is the place in rotation where the clutch engages which would do something to cancel unbalance or alignment, but I don't see how that can happen.
Things checked thus far:
There is no slop in the PTO shaft or the clutch that I can find, it spins freely and engages solid. The clutch adjustments have all been checked and they are even and in spec for this clutch. There is one counter weight on a pulley coming from the shaft out of the engine, it is positioned from the factory. I did tear this motor apart to repair a leaking rear main seal and was careful to bolt everything back in the same orientation as before. If a shaft was bolted in the wrong orientation I would imagine that it would always vibrate anyway so I don't know how that can be the issue. I bought this unit used with the leaking rear main, so I cannot say if it was vibrating prior to taking it apart but the guy selling it didn't mention anything and I did run it a little bit without issue.
I have replaced the U-joints in the PTO shaft.
The gearbox shafts are solid and have no play.
Blades are balanced and tight spindles are good, belt is tight and in good shape.
The only thing I can think to do next is to take the balance on the pulley and move it in 90 degree increments to check for vibration, the shaft out of the engine could only have been bolted in place in 90 degree shifts so one of them would have to align it again.
Any advice or pointers that anyone can offer at this point is appreciated.
Thanks.
