Alternator rotor bolt Loose ?!?!

:ohmy: I have never run into this in over thirty years of messing with these things.
This morning I was going to take my bike for a spin. Low and behold the starter turned but the engine did not. The first thing that came to mind was a bad starter clutch. This was totally unexpected because i have never before had a stitch of trouble. This was the first time this has ever happened. I took the bike in the garage and removed the alternator cover, removed the reduction gear and gave the gear a spin. Huh everything turned just like it was supposed to. With the exception of the crank shaft. The bolt holding it to the crank had loosened up????????? WTF. Any ideas why??? Should there be Locktite on that bolt? There is no Wudruf key just a taper.

Is the tapered end of the crankshaft gaulled? It happened to the PO of my bike(78 KZ1000A2). That bike didn't have a woodruff key either. I'm not sure why it happens, but mark1122 told me about the same problem with one of his bikes.

Hey Otakar,I had the exact problem with one of my KZs.This how I solved the problem.First of all there is 2 styles of rotors one keyed and one not.You have the one that is not,same as me.There are 3 different thicknesses of gear dampers avaiable.you have to assemble the complete assy without one in there you put a little ball of clay where the damper goes do the assy then take it apart and measure it to determin what size you need.(they are still avaiable from Kawi)I bought all 3.I went through this hell a few times with the same result,rotor popping offas soon as the bike fired.I inspected the contact surfaces of the taper area,Put some machinests ink on(a very light coat)and torqued it up.I found that the surfaces where not a perfect match and thought this is probably normal as they would reqire proper torque to mate up.I was wrong.I spoke with a Kawasaki God named Gord Bush and he advised me to lap the 2 parts together whitch I did.I didnt use lapping compound I used some mothers aluminium polish.Took my time and had a beer while I did it.Finally before final assy i cleaned out the theads in the crank taper with a tap and some brake cleaner,cleaned the bolt with a wire wheel.put on some RED locktite and assembled it.Let it sit overnight.checked it the next morning with the cover off,and it all held together.Hasnt been a problem since. You gotta torque the unkeyed rotors to 95 ft/lbs,the book says never hit it with a hammer(you could destroy the magnetisum,I gave it a tap using a piece of 2x4 for a drift before I torqued it.Whatever you do DO NOT let that rotor spin with the engine running itll chew the shit out of the taper on the end of your crank.Ive seen the results of this and its NOT GOOD.
Hope this works for you
Jeff

I just talked to a local racer who rides a 1500cc GPz. He said it has happened to him a few times on the bike. He stated that is a common problem on hi compression motors. He told me to lap the tapers into each other, put some locktite on the taper and tighten with an impact wrench. That's what I did. The whole job took me about an hour.

If you put locktite right on the taper its gonna fail again.That surface needs to be clean as a whistle where the 2 tapers meet.Ive already gone trough this nightmare.

My 82 1000/ 1100 FSM Says 116 Foot pounds for the Rotor bolt, Tighten then loosen and re-torque. Clean taper with a high flash point solvent. Also says if parts are replaced then different thickness dampener may be needed, there also different thickness thrust washers, etc.

The same thing happened to me, took me 3 trys to get it right, loctite and an impact did the trick.

What does lapping the taper mean?  I am having the exact same problem. Changed out the motor clutch and put all back together and used red lock tite…it worked 3 or 4 times but then failed.
can someone explain to me to exact way to repair this?  This bike has been nothing but problems for me…I thought I had the right idea…obviously not.
thank you 

Lapping the taper means use a small amount of lapping compound on the taper until it becomes even by sight. Clean thoroughly so none of that grit gets in the engine. Easy on the red locktight. 
Steve

You will need to buy some lapping compound, which is an abrasive paste. Disassemble the alternator and carefully clean both the crankshaft taper and the opposite taper inside the rotor. Apply some compound to the taper and then carefully, and gently slide the rotor onto the crankshaft until it lightly makes contact, then rotate the rotor back and forth by hand so the compound begins to polish the two tapers. After a bit, pull the rotor off, carefully clean the surfaces and repeat. Each time you clean off the surfaces, pay close attention to the polished areas on both pieces. As the compound removes the high spots, the polished areas will get more and more uniform. Ideally, you want a fully uniform look on both parts, but this may not be entirely possible, depending on the severity of the damage.Once it is as good as you think it can get, clean, clean clean the parts, and reassemble.Do not leave any specs of the compound behind, for they can come back to bite you in the heiny later.

Wow. resurrecting a fourteen year dead thread. Is this a record for KZR?

Be careful when lapping the taper.
Going too far ( which does't take much ) can reduce the clearance for the starter gear and associated shims for the needle roller which can cause the starter gear to bind and drive the starter motor at the very least.
Also never apply loctite to the actual taper, just non permanent 'blue" thread lock to the rotor bolt threads.
The crank taper and rotor must remain metal to metal contact.