Excessive rotor noise

[FOZ1A]

Lads i need some advice! Just finished top end rebuild, took it for a run and heard a noise from the alternator,a high pitched whine sounding like is was revving to 20k! Got home no problem, took the cover off, smelt burnt inside, but oil is getting there and oil level in motor spot on. Any ideas/help would be appreciated!

foz

[zed1015]

Could be the starter clutch not freewheeling and then driving the starter motor which would explain the high speed whine.
Check that the gear can be rotated easily by hand in a clockwise direction.
Other than that it could be the usual loose rotor spinning on the crank taper.

[FOZ1A]

Thanks for you help but, gear can be rotated freely and rotor solidly mounted. Apart from that how can i check the the starter clutch is freewheeling?

foz

[zed1015]

If you can turn the gear clockwise by hand then the clutch should freewheel.
To check, just turn the engine over by the kickstarter (with the alt cover removed ) and make sure the starter gear remains stationary when the crank and rotor rotate.

[Garn 1]

I think Zed1015 is on the money. However, when you say, sounds like, 20k revs and a whine, it would leave me to believe the starter motor has broken a shear pin on the pinion and the starter motor is spinning out of control.

I have seen this happen on old cars. I think it was to do with some part of the starter becoming magnetised and acting as a self propelling Motor/generator Probably worth looking at the solenoid as well.
RegardZ.

[Taffus]

I had this on my GPz, it was the retaining clip in the alternator cover touching the edge of the rotor. Al (Zorded) gave a slight tap with a punch which seated it properly....

[zed1015]

Another thought !
The stator could have come loose and is contacting the rotor which would explain the whine and the burnt smell caused by overheating alt windings.
Also if the alt case has been off during the rebuild then possibly a location dowel has become mislaid allowing the stator not to sit central and create the same result.

[Al]

The Z1R regularly shears one or all of the three socket cap screws that hold the starter clutch to the back of the rotor. The starter clutch is still able to be driven by the remainder of the shaft but the sheared heads can contact the starter freewheel and in extreme circumstances will drive the freewheel foward by locking into the lightening holes which have been 'let' into it.

AL

[FOZ1A]

Thanks for all the advice. I did all the checks and found that the gear did not freewheel. When i refitted the starter clutch, just nipping up the bolt would cause the gear wheel to lock solid. It turned out to the the shim between the rotor and gear wheel was too thick, popped in a thinner shim and its sorted. 1015 was bang on with his suggestion!

foz

[Z1parR]

Aye he's a clever bugger is Rob

[zed1015]

Aye he's a clever bugger is Rob