Damaged alternator

[Dimo]

Hi everyone,

 

A friend's Ballabio suffered a bad alternator damage a couple of days ago and the cause of this is a mystery to us. Bike was running just fine, but the alternator voltage seemed a bit low at 30 Volts, so the stator was pulled out to be checked and then replaced without any additional intervention. It is possible that the two yellow wires were swapped during re-assembly, but as I understand from another topic this has no effect on the alternator performance. After the stator was replaced, a mechanical noise was heard from the alternator, which shortly escalated to the bike losing power and soon after starting to smoke and almost catching fire. 

The result was an almost melted rotor. See picture below and attached.

 

https://goo.gl/photos/BNgKgb87mNx694XX9

 

What is also very worrying now is that the rotor cannot be removed. It is so stuck that it almost seems welded on place. Does anyone have an idea what might have caused this havoc? A new alternator is on its way and will be replaced as soon at arrives and once what is left from the rotor is pulled out. Any advice on how to proceed and what to check for?

 

Your expert opinions and advice would be highly appreciated.

 

Dimo

[Scud]

Wow, at least there wasn't a fire. I can't offer any advice about removing that part, but while you're collecting parts, you should consider a new seal around that shaft. Maybe consider a new voltage regulator too.

[czakky]

Yeah, it doesn't look like some heat and PB blaster is gonna bust it loose... Wish I could help.

[MartyNZ]

Hello Dimo,

If that was my bike, I'd do this to remove the damaged rotor:

1) Remove both exhaust headers.

2) Undo both oil hoses from crankcase, and tie them up out of the way. Tape some rag over the ends of the hoses, and cap the crankcase fittings, so debris can't get in.

3) Fit a puller, heat the remains of the rotor, and try pulling it off. Heat helps, as aluminum expands more than steel. Hotter is better, keeping in mind that the engine can easily get to 120 deg C, so heating that hot is ok.

4) If that doesn't work, file a flat in the rotor, two places on opposite sides. Take care not to let the file touch the crankshaft or the crankcase. The idea is to make the rotor boss walls thinner so clamping loads on the shaft are reduced. You will also be able to fit an adjustable wrench on the flats to assist breaking it loose. Try turning the rotor back and forward with the wrench. It may come loose. The woodruff key between the rotor and the crank will stop it from turning, but wriggling may loosen it. Heat and pull again.

5) If the rotor is still tight, now you need an alert and useful friend. Get a big lump of steel like a 5kg bench vise (without the bench), and have him hold it against one flat you filed on the rotor. Firmly. If he messes this up, you risk bending and buggering your crankshaft. You get a steel cold chisel and a BIG hammer, and hit the thinnest part of the flat you filed, opposite to the bench vise, or whatever you used as a reaction mass. You are trying to stretch the diameter of the rotor, so it will become looser on the shaft. You need to leave a chisel mark along the rotor flat, both sides, deep enough to stretch the rotor, but not deep enough to damage the shaft. Try pulling the rotor after every hit.

Hope this helps, Marty

[stewgnu]

0r an hour or so's careful, patient work with a fresh hacksaw? Which could be less brutal than firing heat everywhere and smashing your bike about with a lump o iron?

That's been my final resort on various metallic probs anyway. A good, sharp, small cold chisel to compliment the hacksaw and finish the job is often useful too.

 

Best of luck with it.

Stew

[Kiwi_Roy]

No idea what caused it but I doubt it was anything you did, perhaps the rotor was cracked and already rubbing overheating and lost some of it's magnetism (trying to explain the low Voltage). We had one guy on here with a broken crankshaft but I think you would know about that.

 

 

Sent from my shoe phone!

[Dimo]

Thank you, guys, for your comments, suggestions and recommendations! Every bit of help is very welcome!

 

This is how we approached the problem today (pic attached). After several heating and pulling sessions the rotor slid out some 5-6 mm. Tomorrow the effort will continue. 

 

 

[MartyNZ]

After several heating and pulling sessions the rotor slid out some 5-6 mm. Tomorrow the effort will continue. 

If the rotor damage has swaged the rotor keyway tight behind the key, then it may never pull off. I suspect that you may still need to do some filing (or hacksawing) to allow the rotor keyway to open. See picture attached.  

[Craig]

A dremel tool with a cutoff wheel will really help here. 

[Dimo]

 

After several heating and pulling sessions the rotor slid out some 5-6 mm. Tomorrow the effort will continue. 

If the rotor damage has swaged the rotor keyway tight behind the key, then it may never pull off. I suspect that you may still need to do some filing (or hacksawing) to allow the rotor keyway to open. See picture attached.  

Alternator Rotor Key.jpg

 

Exactly, MartyNZ! This is what has happened apparently. Pulling didn't work as you have predicted, so the Dremel did the job. A very difficult job! The rotor is, however, finally out and there is no visible damage to the shaft, seal or the surrounding area (apart from the plastic flange in front of the alternator which has melted). The question about what other electrical bit might have malfunctioned still remains though, so a new voltage regulator will be on order shortly.

 

Thanks again to everyone for the input and advice!

[MartyNZ]

The question about what other electrical bit might have malfunctioned still remains though, so a new voltage regulator will be on order shortly.

As you say, the bike could still have the original charging problem.

The regulator may be OK.

The workshop manual says this:-

"THE REGULATOR IS CERTAINLY DEFECTIVE IF: After having isolated it from the rest of the system short circuits can be detected between the earth (aluminum casing) and any of the output cables".

See also extract from manual attached.

Perhaps you could check that the regulator and the battery are well grounded, and the 30 amp charging fuse has been replaced with a separate 30 fuse & fuse holder after the new alternator is fitted.

KiwiRoy has written a lot of helpful comment about this on this forum.

Marty.

WMV11_Alternator&Reg.pdf

BTW, the page from the workshop manual attached shows that 30V AC from the alternator could be OK, depending on engine RPM.

Edited April 28, 2016 by MartyNZ

[Kiwi_Roy]

You can do a couple of tests

Voltage Reference
Locate the male/female connector coming from the loom, the female should have 12 volts on it with the key On, now if you move the probe from chassis to battery + you will read about half a Volt provided you still have the original wiring.

Diode Test
If you have a meter with diode test range measure the regulator from each yellow to the double red, typically reads about 0.5 Volts. You can also do that test with a single cell and flashlight bulb in series, it won't be as bright as a direct short because of the half Volt drop. From the regulators I have pulled apart one of the diodes will melt off the heatsink if it's been overloaded badly, this would show as an open circuit or high reading in the diode test.