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7790 Breaking Flex Disks

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LBS
My 7790 is breaking the flex disks on the driveshaft WAY TO OFTEN! (Twice!) when it does it tears everything up. Is this a normal problem with the 7790? if not, that little 2-winged thing on the BGB shaft that holds the disk was missing the allen setscrew and sliding back and forth so i put a setscrew in. Now when the engine bounces forward and back the disks have to take it all. Should I remove the setscrew or are my engine mounts bad? Also, the BGB is worn quit badly, is it the gear teeth or is the gear loose on the shaft? Any help would be appreaciated. Lawrence

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MikeES
Lawrence, check your motor mounts. I know the mounts on the diesel are usually bad after a few years. You will not be able to tell much difference before and after the new motor mounts (that engine really shakes) but I think it will solve your flex disk problem, and others. Yes there should be a set screw in the BGB ( 2 winged thingy). Good Luck! Mike S.

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HubbardRA
Not familiar with a 7790, but my two tractors both have flex disks and have never broken one. On my tractors the engines bolt solidly to the frame. There is no front to back motion. Also the bevel gear shaft should not move front to back. In any fixing or reassembly process, the set screw that you are talking about should be the last thing tightened to allow part to slide on the shaft during assembly and eliminate any undue loading on the flex plates. Rod H.

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LBS
Yes My other two have engines bolted down solid and they work great. but I was wondering if these were different due to the flexible angine mounting system, It allows about 1/2" back & forth and 1" up & down and 2" tilt, which is very nice. It is the smoothest mower I ever mowed with LBS (Lawernce B Shafer with a very heavy mower!)

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Dutch
Lawrence, You should get a manual specific to the 7790. Since the Lombardini uses flexible motor mounts, the drive shaft flex joints may be different from the gas engine models. Do your flex discs use the special heavy "washers" like the gas engine models? Is the curved side installed correctly to prevent cutting into the discs? Regarding your BGB, start by removing the inspection cover and determine what's going on (bad bearing, broken snap ring, loose gear, etc.) before you do some serious and expensive damage.

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UCD
The disks on my 7790 are the same as any 7000 0r 7100 and 900 series tractors. I believe the problem is in the rear yoke not being secured when the shaft is installed it should have just has enough room to slide into place. I have broken 3 sets in 17 years and that was because i hit something solid with the blower and stoped tractor dead in its tracks. This & $1.00 might get you a small coffee Maynard aka/UCD http://www.simpletractors.com/club2/uploaded/UCD/7790%20drive%20shaft.jpg

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