KZ750 Starter Clutch/Rotor loose issue

Hi Guys,

I know from reading KZR that this issue is not a new one and have tried several of the "tricks" I have read on others posts......

I have put lock tight on the thread of the flywheel bolt, sanded down and cleaned the shaft .... yet after doing this 3 times already I will put the bike back together, fire her up and ride for roughly 3 miles then shut down ONLY to have the flywheel spin loose again? I have used an impact to tighten the left handed nut as well??

any ideas??

Make sure you have the correct bolt and washers so its not Bottoming in the crankshaft. Also check that the Rotor is being pressed onto the crank properly at the rotor/ crank end. The Rotor should still be further out than the end of the crank, after torquing, you would have to remove the bolt again to check.

Did you torque it to the specs from the FSM?
I have had my B1's off twice because of the allen bolts in the clutch backing out and once to replace rollers/springs. But never had an issue with the assembly working loose on the shaft.

UPDATE:

Okay I took it all apart again and it started beautifully! Rode it around for about 5 minutes.......came in and put on my helmet and glasses to be a lil bit more serious and .... she died. Thought I had her all warmed up since she was purring like a kitten.

Again, the restart had that starter spin and sound like the same result???

Took off the side covers and .... TIGHT? The bolt was perfectly tight and not loose like before however, its like the starter is not engaging the rotor/flywheel. I rechecked the lil springs to make sure they are still very firm in the clutch and allen heads tight - they are in great condition too?

Everything seems in its proper place and moving freely as I take it apart again? so I again put it all together and try to restart......that same starter spin noise.?

It sounds like a car starter when it isnt connecting to the flywheel... the starter spins but the bendix doesnt connect to the flywheel to initiate the start.

Torque setting is within the limits of the specs too?

previously I read in forum about using lock tight on the threads and that seems to have worked great! But, now I have another issue with the same result?? Could I have damaged something or possibly a bad pience on the starter????

Thanks! I did recheck it and it looks right. earlier today after reassembly it started great and I rode it up and down the street with it running very good. I basically killed it letting it idle before getting hot enough to turn off the choke and ....

the same starter spin issue returned??? Asking myself could it get HOT after riding and something else be the cause now? I let the bike sit and cool off for over 2 hours and same issue.

osage,

Yeah when I had ORIGINALLY took the bike apart I noticed the nut spun loose causing the rotor to have about 1/8" slop in and out. I guess I assumed this was the only reason for my issue after reading the forum and thinking it was actually the allen clutch bolts before this inspection.

I tightened the nut and reaasembled. Started fine and rode for about 2 miles came home and shut the bike off...then tried to restart and spin noise again. took apart and seen it was losse again so I then took it apart cleaned the shaft and inside of rotor THEN retightened to spec with lock tight on the the threads of the nut. Pushed outside this morning and again started great and rode fine until shut down and another starter trial with same starter spin noise? THEN i took side covers off and seen the nut was perfectly tight this time, lock tight worked....replaced the covers and it started again!! rode it around the subdivision .....

Shut it off and guess what? spin noise again with no start! took apart recheck and everything looks fine.....push outside to retry a start and now same thing. spinning noise. ugh?

Having a hard time making out parts #'s in Motorhead GIF. but I thinks its #'s 23, 24 & 25 that I had to replace even though I could not see any damage. Inspect number 19 & 21 for damage as sometimes they can crack. The new springs, spring covers and rollers got the over running clutch to work. As mine made the same noise as yours is.
Hope your kick starter is working until you can get this worked out.
I got all my parts from Z1 Enterprises.

So I have made another attempt to check the rotor....the bolt was now ONLY snug and the rotor itself was able to spin behind the bolt head!

So I retorqued and pushed it outside....started right up!! Went for a ride and again wanted to retry a restart and IT DID START! But the next try, it...SPUN again.

Why wasnt this designed with a key???? ha ha

I will contact Jeff my old school Kaw Mechanic and let him know I am bringing it to him to solve. ( sad face ) Unfortunately it will sit for 2 weeks waiting for him to be available.

unless anyone else has had this issue and can help?? seems most others have had the clutch allen bolt issue but, mine are perfectly tight and springs are in great shape. I just cannot get the rotor/flywheel tight enough to not spin and cause the LH nut to lossen which makes the rotor slop worse?

I appreciate everyones input, THANKS! I am sure I will be riding again soon.

What's the history of the condition?
Did it start happening out of the blue?
Did it start happening on a recently acquired bike?

Perhaps the flywheel was replaced with one that appears the same but is from a different model?

Good Fortune!

my dad bought it new in 1979 and has basically 12,975 miles. I basically was handed it to restore after it was in the garage for over 7 years....this is all just recent and has me puzzled? I rode it quiet a bit when my dad had it too so this is an out of the blue situation since i have had it running for about a year.

I had been riding it to work daily with good weather and really trusted it as much as you could a bike this age until now.

What a great bike though...this will get figured out and back to enjoyment!

Here is the 79 KZ750 when I saved it from the garage sleep.............

I checked at the KZ400 forum, where with undamaged parts, the generally accepted solution seems to be:

Scrub both mating surfaces clean with acetone;

Use Loctite Stud and Bearing Mount;

Tighten with air impact wrench.

Realizing this procedure has already been performed multiple times, followed by persistent loosening, am wondering if acetone and Loctite Stud and Bearing Mount and air impact wrench were all used as suggested.

Good Fortune!