Z1OwnersClub GB

Hi All, My recently rebuilt Z motor keeps on spinning the generator on the crankshaft when trying to start. It has the old style taper and keyway for the woodruff type key, but the rotor is the later (i think) item which does not have a keyway.
The bore of the gen is a bit grooved but only right at the end, say 2-3 mm in. I have lapped the tapers in as much as i think i can do with grinding paste, although with a bit of a groove at the end its never going to fit too well is it!
I have had 2 attempts now with the last attempt using Loctite bearing adhesive (the orange stuff) but alas it has already come adrift.
Has anyone got experience with this problem and how did you solve it?
Cheers

take the rotor to a machine shop & get them to cut a key way in it

The cranks with a keyway only use an 8mm bolt and this cannot be tightened enough to prevent a keyless rotor from breaking loose, Hence the keyway needs to be used.
The later 1000 engine without keyway also upsized the bolt to 10mm which can be torqued enough to hold the keyless rotor.
The only solution is to fit the correct keyed rotor and woodruff key.
A light lapping of the rotor as you have previously done will ensure the best fit but DO NOT apply any sort of Loctite to the taper - only the bolt thread if needed.
The rotor should be a dry fit on the crank.
Be wary when lapping the taper as this moves the rotor and entire starter clutch assembly closer to the cases which can cause the starter gear to bind and drive the starter motor.
If this occurs the dished damper rubber can be thinned slightly by rubbing it on some wet and dry placed on a flat surface (a mirror will do)

Thanks Zed1015, i suspected this may be the proper and maybe only remedy. Don't suppose you have a keyed rotor in your vast hoard of parts?
Re. the damper washer - some parts diagrams seem to have these in and others don't there is not one fitted to my engine at all and i see there are several options listed as well - 6.3t, 7.3t, 8.3t. I suppose the "t" denotes the thickness of the washer? Any ideas which one i should try first?
There is only a steel plated thrust washer fitted to mine which sits in the recess in the back of the starter gear. Confusingly the starter pinion lines up perfectly as is.
Thanks for your advice

My z1000 has done the same thing, but has a z1000 crank and a keyed rotor

Zomerset Zed wrote:Thanks Zed1015, i suspected this may be the proper and maybe only remedy. Don't suppose you have a keyed rotor in your vast hoard of parts?
Re. the damper washer - some parts diagrams seem to have these in and others don't there is not one fitted to my engine at all and i see there are several options listed as well - 6.3t, 7.3t, 8.3t. I suppose the "t" denotes the thickness of the washer? Any ideas which one i should try first?
There is only a steel plated thrust washer fitted to mine which sits in the recess in the back of the starter gear. Confusingly the starter pinion lines up perfectly as is.
Thanks for your advice

Sorry! Haven't got a spare rotor.
Have never had any starter gear fitted with anything other than the dished rubber damper so would be interested to see a pic of what you have got there.
I have seen some very badly worn or hacked about ones though so maybe what you have is the remains of one if a previous owner has had a go at it or maybe it's a home brewed solution.
The rubbers come in 3 thicknesses denoted by 1, 2 or 3 stars moulded on the inside lip.
I would get a 3 star one and then it can be gradually reduced in thickness until you get the correct fit.
Make sure you get one from Z1 up to the first Z1R that has the same alt rotor set up.
The damper rubbers from the later MK2 motors onwards with the dished rotor have a bigger hole in the centre and won't sit central.
It only needs to be thick enough to stop the starter gear from dragging.
This means being able to freely turn the gear clockwise with very light pressure .
Forgot to mention that in extreme cases, overlapping can cause the whole assembly to nip the bearing and/or the gear hub between the bronze thrust washers on the crank and lock the starter gear and produce the same results.
Very unlikely but I've dealt with that a couple of times and had to resort to either light machining of the face of the starter hub and /or reducing the thickness of the thrust washers to get the clearance back.

Dunlop4 wrote:My z1000 has done the same thing, but has a z1000 crank and a keyed rotor

Maybe there's a trade on the horizon there for Zomersets none keyed one ?
Z1000 one done correctly shouldn't spin with a light lapping and the correct torque though unless the taper is properly mangled.

I have a keyed rotor I could swap

Thanks everyone for the help (spesh Z1015 again) i will get back to you soon. Life mad at the moment

Keyed gen from Keith now fitted and is holding. Still have slight issue with intermittent free-wheeling of starter ring gear but will try a thicker rubber washer (lip seal) to solve this. Ta everyone for your input. Slowly knocking things off the snag list