When assembling drive sprocket and alternator rotor the rotor key will not sit into its key way due to interference from rotor spacer. The easy solution is to shorten key by 4mm but if standard parts don’t fit it’s usually assembly at fault. The sprocket sits snugly onto taper without key, the spacer is hard against sprocket with recess outward but interferes with key by approximately 4mm. Can anyone give me pointers toward a solution, or is it a normal procedure to shorten key.
I seem to recall the…
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I have two sprockets,…
I have two sprockets, spacers and rotors from other engines I have fitted belt drives to which are identical pairs, I just don’t have an old key to compare. May carefully take small amounts off the key until everything fits. I can’t remember any details when fitting rotor to other engines but the key will only locate with about 9mm of rotor slot, this seems less than should be used considering the rotor is 34mm wide.
The engine is on a stand so have no primary to check with stator but at present just test assembling.
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The key is to ensure the…
The key is to ensure the timing marks on the rotor one up correctly, the rotor is held in place by the crank main shaft nut being torqued up correctly and staying that way.
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I seem to recall the alternator spacer on pre-Mk3s being undercut to clear the key. Then on Mk3s the key was truncated to fit a flat faced spacer.
The keys I have in the drawer have all been filed down. They're between 15mm and 12mm overall length.
I wouldn't be worried about trimming the key to fit so long as you keep the maximum engagement with the alternator slot.
[Edit] I just read your post again and you say your spacer has a recess. In that case I would fit the sprocket, fit the alternator rotor without the key and bolt it up. Then fit the stator. Do the rotor and stator line up? Because with the right sprocket, spacer (without shims) and key, you should be able to fit the key without modification. If the rotor stands proud, it's the wrong spacer.