721D Flex Disc Failures

[bwoodmac]

Purchased a used 721D that keeps ripping the flex disc- mostly on the gemini drive end, On closer observation I noticed the previous owner did not use matching motor mounts leading to a vertical issue, so I ordered 4 new motor mounts which by visual observation seems to have corrected the vertical misalignment. There was also a lateral misalignment so I loosened the engine studs and adjusted the engine to visually realign the crankshaft drive end to the gemini drive (I don't have a dial gauge), I then bolted the drive coupler directly to the engine drive end (no flex disc used) and to the gemini drive such that with the bolts tight on the crankshaft side I can loosely move the coupler on the gemini side so that the bolts are loose and move freely (no flex disc installed simply the drive coupler from crankshaft to gemini). Before I spend another $60 only to maybe once again have a failure, is there someone who has had similar issues and found a fix? I made two cheap flex disc just to check for wobble visually. With the engine running at idle the shaft visually seems to spin without wobble, even up to about half throttle, that's as high as I pushed it. No observable damage to the mower frame, no cracks no signs of welding repairs, so frame seems original and in alignment. Apprciate any and all suggestions.

 

[Auto Doc's]

Sounds to me like you found and corrected the alignment problem. Never heard them called a "gemini drive".

 

[bwoodmac]

Sounds to me like you found and corrected the alignment problem. Never heard them called a "gemini drive".

Thanks for the reply!

• Gemini Drives: Many 7 series models used these drives until about 2005. Models that used Gemini drives include the 718K, 720K, and some 721D and 725K models. Gemini drives combine the pump and drive motor in one unit on each side of the mower.