I second what Mike said. I would probably also try some heat on the nut. Or try partially slotting the nut with a Dremel or a die grinder and then splitting it with a chisel. Shouldn't be a big deal to tig or mig a new flat on the block..Here's what I'd do:
Option 1) Using the nut on the other side, spin the axle until the edges are parallel to the swingarm. Grab a spanner that fits the flatsides of the axle on the chain side, grind off the outer edges of the spanner so it fits in the detents of the swingarm. Ratchet on the brake side, modified spanner on the chain side.
Option 2) Mig weld a flat bar to the chain side of the axle. You can grind it off when extracted.
Hail Mary option: Slightly loosen the chain tensioner bolts, stick a screwdriver between the chain and rear sprocket. Have someone keep the bike pushed forward, this will apply locking tension to the axle and you might be able to loosen off the nut. This risks hurting your sprocket and chain, but if you're doing this to replace them it might be OK.
When you put it back together, place a dab of copper anti-sieze on the axle threads. If I recall, some FZs have an incredibly high torque spec -- over 100 +ft lbs -- under that pressure I'd be replacing the nut ever few times it's removed.
This happens even when assembled correctly. The torque specs are so high, 108lbs, that the threads on the axle and nut will be distorted, probably tiny bits of thread shrapnel and a touch of galvanic corrosion are freezing the nut stuck. The force needed to release the nut exceeds the sheer strength of the soft aluminum tension adjuster so it fails.has a good statement on cause of this (brianp)......."When assembled correctly - with the flat correctly lined up in the adjuster block so that the axle properly slides all the way in before tightening the axle nut - the adjuster block will never get chewed up like that in the first place. "
This happens even when assembled correctly. The torque specs are so high, 108lbs, that the threads on the axle and nut will be distorted, probably tiny bits of thread shrapnel and a touch of galvanic corrosion are freezing the nut stuck. The force needed to release the nut exceeds the sheer strength of the soft aluminum tension adjuster so it fails.
Just a bad design. I think this is evidenced by the fact Yamaha altered the axle bolt on '17, and there is an aftermarket fix for the pre '17 axles.
Had this happen on my 2009 GSXR1K. Still no idea why as it was always tq to spec and always clean but anyways. Had it cut off and replaced axle/nut/blocks.
This happens even when assembled correctly. The torque specs are so high, 108lbs, that the threads on the axle and nut will be distorted, probably tiny bits of thread shrapnel and a touch of galvanic corrosion are freezing the nut stuck. The force needed to release the nut exceeds the sheer strength of the soft aluminum tension adjuster so it fails.
Just a bad design. I think this is evidenced by the fact Yamaha altered the axle bolt on '17, and there is an aftermarket fix for the pre '17 axles.
The axle and nut should be replaced. You can use a Gilles titanium axle nut (crazy expensive) and a new '16 axle or upgrade to the the axle & nut used on a '17. Yamaha updated the design to eliminate this problem for '17, you need a new axle, nut and adjusters. Also, check the '17 manual, if I recall the torque specs are back to the normal 80-85lb range.an aftermarket kit? I hope the op reads this before ordering new parts. good info for the poster.
makes total sense i wonder if there is aftermarket fix for the gixxers as my L2 1000 did same stupid thing had to hit up ebay in a panic and get one off a total different make model bike which lots interchange .
[...]
Just a bad design. I think this is evidenced by the fact Yamaha altered the axle bolt on '17, and there is an aftermarket fix for the pre '17 axles.
Why is the adjuster block made of aluminum in the first place? Couldn't they use something harder?