-Woodruff Key Trouble-

Hi folks.. First time Z1 engine builder here. I've put together a 1975 Z1 900, using a 1327cc APE big block kit. I've had it out for a few rides, and it's a gas.

Problem is, twice I've sheared the woodruff key on the crankshaft alternator side. After the first time, I cleaned things up, and used some valve grinding compound to get the tapered surfaces smooth. I used a fresh woodruff key and torqued to the recommended 18 ft/lbs. The starter turned the motor over briefly, then the key sheared again.

Is there any reason not to put things back together and weld the rotor to the crank? I think there is room for a bit of welding, through the circular opening at the rotor end. Heaven forbid I'd need to take it off again, but even then I could probably grind it free with a Dremel.

Has this ground been covered by anyone else? Am I about to make a serious mistake..?

Thanks in advance -- Mark

Skid, While my manual is for a 1000, It states torque is 51 ft/lbs. and seems to me to be reasonable where 18 does not. one of the reasons torque value is important in this area, is that the starter clutch mechanism is critical for clearance.welding is NOT an option. do some research. if 18 ft/lb is correct, replace stator, if stator is all aluminum, it's possible someone in the past has over tightened and distorted it. luck G

i dont have any pictures but if youre really ambitious you can cut a longer flat groove in crank for full size woodruff key in crank.are you trying to use the electric start ?

Hey, thanks..

Pretty sure the 1975 Z1 has 18 ft/lb torque for the rotor bolt. I've read that some other years have higher torque specs.

Cutting a longer notch for lengthier woodruff key would mean splitting the cases, etc, to get the crank out. That's a drag, after working on this bike for a couple of years, and getting a taste of riding it.

I do need that electric start, though. There is no way to kickstart this thing now, with the extra cc's.

-Mark-

i kickstart most of my bikes including my 1327,when its together anyway! :laugh:

retard your timing a bit and it will be easier to kick or to electric leg. if you have a problem go to schnitz racing and look for there ignition contoler it has setting for start ing it auto maticly retards the timing for starting.by the way your only kicking over a 331.75 cc cylinder at 1327 so it should not be that much of a problem to kick it over. only one cylinder at a time is on the compession stroke. sso all your really kicking over is a medium sized single. if you have to add a bit of lentgh to you kicker.

In addition to the other solutions provided, you could also get a larger key and shape it to fit tighter in the crank and the rotor.

81 J motors were known for spinning the rotors. They don't have a keyway. This was the Factory Fix for the J.

Remove rotor and clean crankshaft end up with 600 paper. Put some lapping comound on the end of the crankshaft. Hand lap the rotor to the crankshaft. Clean lapping compound from crankshaft & rotor. Apply liberal amount of red locktite to the crank shaft. Install Rotor and tighten to spec. Loosen and retighten rotor bolt.

Fix it now or you're headed for a miserable summer...

Make sure the bolt is in good condition and has not stretched.
Make sure the threads on the both the bolt and the crank are clean - if you have any debris in the crank thread, you may be torquing against the debris rather than tightening the rotor.

...also, make sure the cast aluminum part of the rotor has not started to pull away from the hex steel center. If you have any sign of play / crack, replace the rotor.

Skid, the reason your key is shearing is because the starter is kicking back. It's not turning over with enough power. Put a big battery on it with some bigger cables and a good starter and you shouldn't have any problems. I have a 1327 street bike and I had the same problem. I put a Fast By Gast battery on it with bigger cables and it stopped shearing the key. I also put a better starter on too.

I had the same problem with my rotor(1105 engine).
Once it spun,the damage was done.I even tried making my own keys,but it kept shearing them.
A little damage on the inside of the rotor from the first time it spun,and I could not repair it.I pulled the rotor from one of my parts-bikes and after a good cleaning,installed it and haven't had any problems since.
Coming on season 3 with it.

And speaking of starters,remember hey,that a Honda CB model starter has more punch than the factory Kawi starter.
Mid 70's models.
A slight mod is needed,but they do drop in.

Thanks for the responses..

I definitely have some thinking to do. I may need to replace the rotor, as it’s hard to know at a glance whether or not the receiving end has distorted.

I have a fresh Yuasa battery and a new Z1 Enterprises starter, but a Fast by Gast battery upgrade sounds like a good idea.

Applying red locktite to the crank end sounds right, though it makes me wonder if some epoxy, like JB Weld might be more solid.

Retarding the timing might make startup easier. I’m using DynaTek electronic ignition, and I set the timing statically, with the sensor indicating 30 degrees advance. That’s less than the DynaTek instructions advise, and it makes me wonder if I’ve misunderstood this too.


-SkidZmark-