TOPIC:

So two days ago coming off the highway  downshifting at around 40mph on the off ramp my rear locked up and somehow miracles happen and I kept the bike upright and managed to walk away unscathed. Needless to say, I never want this to happen again, could have been really really bad.

The chain appeared to have come off the sprockets and jammed in the swingarm. After freeing it and pushing the bike a few blocks home I started disassembly to find the issue. To my utter shock my front sprocket is gone completely, nut and lock washer fell out of the housing but no sprocket. 

If I remember correctly the 16t jt sprocket I installed did not have a tab for the lock washer and I read it wasn't critical so I assumed the part from z1 wouldn't be wrong. It's been running this way for around 2k mi. I'm doubting this is correct and suspect it to be the source of my issue.

I was already planning on upping the front sprocket to a 17t when down for the winter but that's been sped up now.. After some further reading on here I found biquetoast recommending sunstar sprockets from Dennis kirk as they apparently have the locking tab hole. Ended up needing both sprockets and a new chain, all ordered and waiting on parts to arrive now.

I'm very concerned about this happening again, once installed with the locking tab correctly bent into the sprocket will this be a continuing concern?

Should I use a normal split lock washer between the locking washer from Kaw and the nut? 

I'm thinking I am going to loctite the nut on reassembly unless someone can give me reasons not to. 

Thanks for any help. 
 

Did you use a torque wrench on the nut and if so, how tight did you make it?

 

Yes I did use a torque wrench for the sprocket nut. When bringing this bike back to life I went through the manual and used the stated torque values for everything. Literally worked my way through checking and setting caution and warning items throughout the book. 

Luckily my wife works at a print lab so I had her print out the entire book for me so a physical copy is always handy when wrenching on the bike. 

I would check to see if there's a splined washer you can install.  The splines fit over the output shaft,then after installing & torquing the sprocket nut, bend the splined washer over a side of the nut, effectively locking the nut in place. 

The 750-B3/B4 transmission diagram at Partzilla lists a splined washer. I don't know if the earlier 750B output shaft is the same.
www.partzilla.com/catalog/kawasaki/motor...smission-kz750-b3-b4

From what I can tell in the factory manual, the toothed washer they speak of is not splined, but toothed to allow a tab to be inserted in the sprocket and another side bent back on the nut. 

That said I ordered at the same time, the washer and nut from z1 so I can rule out my existing set. 

Any reason to not use blue loctite during reassembly. 

What years does your manual cover?  It may be that the later models had the splined washer >> my 81 KZ650-CSR uses the same one & the FSM says to install the nut then bend over 1 side of the washer against the nut.

ps:  I didn't know what year your 750 is & didn't notice the username til now.

My bike is a 77 750b2 my manual is for  76-77 with an amendment for 78. It seems from everything I can find so far that the splined washer is for later years. I will try the new washer and some serviceable loctite and toss this up as a fluke as it seems like I have all the parts right 

I use a splined washer on my KZ750. Its only listed for later models but i believe this will work for you as I have one on my 1980 kz750G which is nearly identical to the B

www.partzilla.com/product/kawasaki/92200...a2e14d027b78e09c0813