Stuck alternator rotor

[Il Fiorentino]

Hi all

I have a '76 LeMans and I am attempting to remove the alternator rotor. I purchased MG Cycles tool and proceeded as follow: insert tool in rotor screwing it in all the way
Using a ratchet wrench, tighten tool really hard
Rapped on the head of the tool with hammer
Repeat tightening and rapping until I cannot turn it anymore.
If it were a solid piece I would try a little heat but having all the wiring I don't think it would be a good idea. Applying more torque to the bolt/tool is risky, I already feel a lot of flex and I am afraid it will snap. Over the years I have developed a pretty good feeling about where the limit of a given bolt is and I think here I am very close to it. Does anyone have any idea how I should proceed? I suppose after 30+ years it is stuck pretty well but I need to inspect the distribution chain (73.000 km.).

Thanks in advance for your help

Giordano

 

[Trout]

The tool I have from MG looks like the alternator bolt & has an allen (hex) head. I don't remember having to go real tight and hitting it with a hammer. The long part bottoms out on the blind hole of the crank and the threaded part forces the alternator to push away from the crank,

If you haven't done so already try taking the tool off and seeing if the alternator is not loose on the crank now.

The crank is a taper fit to the alternator and by over tightening and smacking with a hammer you may have caused the alternator to seat on the crank.

Take it apart & try doing it again the bolt should get tight and then a little more pressure and you should feel the alternator pop. Take tool/bolt out and it should be loose.

 

[Chris R]

The crank is a taper fit to the alternator and by over tightening and smacking with a hammer you may have caused the alternator to seat on the crank.

Here is my two cents,

Smacking the end with a hammer won't cause the rotor to become anymore stuck than it already is however it may damage the threads in the rotor.

I would take two large ballpeens - hold one on one side of the rotor and use the other with a short sharp smack, repeat all around. Tighten the tool as much as you dare between percussions. Hopefully the vibration will break things loose. I have taken off a few rotors and sometimes they require a scary amount of force.

Put a box of rags underneath the rotor as if it does pop you can damage the slip rings.

The less risky method is take a grease gun and make a fitting with the same thread as the rotor (the crappy chinese grease gun I have happens to have the right thread but it has no name on it). Thread it in and pump grease until it blows off. YOu can get a couple of tons of force with this method so it will definitely come off.

This is Pete Roper's clever idea and I have found it works brilliantly.

Once off, I would lap the new/repaired rotor on with fine valve grinding paste and use anti-seize.

 

[Il Fiorentino]

Thanks for the advice. Just to clarify I did not smack the bolt but GENTLY rapped on the tool head to create some vibrations.
I will try the methods suggested and report back.

 

[john zibell]

Thanks for the advice. Just to clarify I did not smack the bolt but GENTLY rapped on the tool head to create some vibrations.
I will try the methods suggested and report back.

Being gentle won't help you here. It takes a good shock to get the rotor to come off. I wouldn't use a 8 pound sledge, but one sharp hit with a 2 to 3 pound hammer is what is needed. If it doesn't pop, tighten the screw again and another sharp hit, repeat if necessary. As Chris stated, beating on it doesn't do any good, but it does take a good hit to shock it loose. If you can do the grease gun thing, all the better. I haven't used that technique, but I can see it's value.

 

[tewrecks]

Tap the rotor to twist it slightly

 

[AndrewGelling]

Chris, sorry to be so basic, but when you refer to lapping with valve paste, do you mean applying some paste to the tapered crank shaft, place the rotor on and grind the two surfaces that mate? I assume you then remove rotor, clean up the paste residue, and apply the antiseize to the taper and to the bolt? Or perhaps antiseize is only for the bolt and engine oil on the crankshaft taper. This goes right to the heart of my question on my last post.

 

[john zibell]

Chris, sorry to be so basic, but when you refer to lapping with valve paste, do you mean applying some paste to the tapered crank shaft, place the rotor on and grind the two surfaces that mate? I assume you then remove rotor, clean up the paste residue, and apply the antiseize to the taper and to the bolt? Or perhaps antiseize is only for the bolt and engine oil on the crankshaft taper. This goes right to the heart of my question on my last post.

Correct on what to do with the bolt and the paste, although in my opinion the rotor bolt doesn't need an anti seize since it is steel to steel. Also I've never seen a need to lap this joint as the manufactured tapers seem to lock well. The taper needs to be dry. The taper is a type of locking joint used by manufactures since the early 1900s (Model T rear wheels are an example) or even earlier. BMW even uses a taper joint on the output flange of their airhead transmissions. Oil only goes on the lip of the seal.

 

[Chris R]

Chris, sorry to be so basic, but when you refer to lapping with valve paste, do you mean applying some paste to the tapered crank shaft, place the rotor on and grind the two surfaces that mate? I assume you then remove rotor, clean up the paste residue, and apply the antiseize to the taper and to the bolt? Or perhaps antiseize is only for the bolt and engine oil on the crankshaft taper. This goes right to the heart of my question on my last post.

Yes to all but it is not critical and as John points out below may be of questionable value.

Correct on what to do with the bolt and the paste, although in my opinion the rotor bolt doesn't need an anti seize since it is steel to steel. Also I've never seen a need to lap this joint as the manufactured tapers seem to lock well.

I do it out of habit - it is not really critical and it may be way too belts and braces but I think it helps both hold the joint when bolted up properly and release the joint when you need to remove the rotor. It also tells you whether the joint was machined right in the first place- you will see evidence of the paste doing its thing on the whole surface area like mechanic's blue. It takes all of 5 minutes so I just do it to see that the rotor and crank match properly.

A proper taper joint should hold to the required torque when bolted up AND release with relative ease when unbolted. That is the point of the joint.

Lapping is standard Caterpillar practice - or at least it was when I went to Cat School. Maybe not so now that CNC machining and ceramic tools mean that things are machined to much higher tolerances.

Same with the anti-seize -I don't think it hurts and may stop the rotor spin welding to the crank if it comes loose - or maybe not. Of course if the taper is proper almost all the anti-seize will squish out so maybe it is a moot point.

I do know that I haven't had a rotor stick in a while but then I don't take them off every day.

And did you get the rotor off?

 

[Il Fiorentino]

Hi all

with the Holiday craziness and the after the Holiday craziness I have not had time to work on the bike, that is until yesterday. I new that the bolt/tool was applying a great deal of force and I guessed I was not far from success but the amount of torque I had to apply to the tool was great and I did not dare apply more. So yesterday I had the idea to grease the treads and also the tip where it presses against the bottom of the hole in the crank shaft. As I was tightening (I still needed a lot of torque I heard a metallic snap and I was sure I had snapped the tool. Low and behold it was in fact the rotor that got unstuck. Man that should no have been so hard, but at list it's done.

Chain looks good, rubber block(the crude tensioning system Guzzi used back then) is in like new condition which makes me think that it never did any real work. Very small indentation where the chain rubbed against the block. All in all better than I expected. I will start a new post with pics about the replacement chain and tensioner.
Thank to everybody for their answers.
A very happy Giordano

 

[Mc Tool]

Dude I had to use a 30 ton hydraulic 3 legged puller to get the alt rotor off my paso crankshaft , and that went with a crack , the gear , the puller and me all wound up on the floor.For what its worth I think that fitting a continuious ( no joiner link ) and the spring tensioner is a good move . The old rubbing block is probly not that worn because its rock hard and I have seen these ( not on a Guzzi ) start to desintergrate

 

[Il Fiorentino]

It sounds like you had a tougher time than I did with your Ducati :lol:
Question: why do you make a point in recommending an endless chain? I thought master link was OK. In fact I was leaning that way, but since I have not ordered it yet I would like to know your reasons. To make the tool to remove the crank shaft nut would not be a problem but more work than using a chain with master link. I appreciate your input.

Giordano

 

[Mc Tool]

I guess its just a mistrust of joining links from way back in my trail bike youth. If you can do it without a joiner , why use one ?.I have to admitt that a guzzi chain case is a much safer environment than a paddock full of rocks, but ( relying on memory here ) I reckon a double width joiner would be a proper bitch to install.
So ... no real reason , just dont like the idea of it .... thats all

 

[theoneandonlymin]

I know that the job is done now but I had a similar experience. I ended up threading a grease nipple on and pumping the rotor off with a grease gun.

theoneandonlymin
x

 

[Il Fiorentino]

theoneandonlymin:

this is very interesting. Chris R. had mentioned it also earlier in the tread as a Peter Roper "trick".
Far from doubting it, I have a hard time grasping the fact that the grease gun would apply more force than the highly torqueed bolt. I understand that it can squeeze the grease at great pressure but such pressure is applied to such a small area (the area of the 8mm diameter for we are only concerned about the force applied to that surface). So if we consider pounds per square inch it would require immense pressure to match the bolt. I repeat that I am not doubting, I just can't see it so please help me understand.

Giordano

 

[Chris R]

I understand that it can squeeze the grease at great pressure but such pressure is applied to such a small area (the area of the 8mm diameter for we are only concerned about the force applied to that surface)

If you look at the end of the crankshaft it is maybe 20mm wide so the force is applied to a much greater area than just the end of the bolt AND a grease gun can develop an amazing amount of force - like a couple of tons. I've never had a problem with this method. It pretty much flies off. Where using the standard method is a bit scary - I am always worried that either I am going to strip the thread or bend the tool inside the crank and be up sh*ts creek.

 

[Il Fiorentino]

All right, that makes more sense to me. Next time I have to deal with it I'll go "the grease gun way" :lol:

Giordano