Question about U-joint/driveshaft noise 1982 XJ650RJ Seca

I took my driveshaft apart due to noting some noise while pushing the bike. In the process I measured the middle gear backlash, and on one lobe of the driveshaft flange I detected excessive backlash, so off came my swingarm, etc. In the process I removed the driveshaft from the swingarm housing and the u joint feels stiff in one direction, the other feels fine. How do I determine if I should replace it?


I am hoping the backlash and possibly the U-Joint gets rid of the noise.

This is following a rebuild including rings and starter clutch (Previous Owner did the chain guide) in which I tried to read the Haynes manual description of checking the middle gear backlash and was convinced it was too complicated. The Yamaha manual explains it much better, so here I am going back to it.

 

Anndddd if I can figure out how to get the video on here I'll do it but it's cross posted to a couple of XJ facebook groups....

 

I recently had my swingarm off on my 750 SECA to address some excess play that was ultimatly caused by the pinch nut backing out after 40+ years. What I did notice was a fair amount of backlash of the output but it diminished as I went up in gear so I chalked it up to a sum of the overall gearpath. The universal was good, no backlash between the input/output yokes and the final was maybe 0.005" by estimation having rebuilt many GM and Ford 9" diffs over the years. What I can't find is a definitive backlash number or tolerance for the overall drive in the manual other than what is outlined regarding the helical output gear, anyone know what would or should be considered acceptable for these? I'm going off the factory Yamaha manual and see nothing at all. In first gear I had roughly 1/2" of total rotation measured from the top of the output flange and this went down to roughly 1/4" maybe less in 5th turning by hand. Seems like an awful lot of gear play considering everything is in mesh.

 

As I said there, I’d recommend replacing the u-joint. There should be plenty here, I probably have a few, too...... I’m in NY
Feel to send a conversation,
Dave Fox

 

I got one on eBay.

Bhratweed, I am out of state now and don't remember the backlash play, sorry.