Vintage BMW Motorcycle Owners

Hello again all,

Having a tough time getting the armature of my R27. I have Vech's tool. Did the tighten, hit bolt head a few times, tighten, hit a few times thing until the tool bent. So, I need a plan B. I straightened the tool now need ideas. Heat has always been my savior in stuck part problems but the armature looks unfriendly to it. Not knowing, but imagining, how the armature fits onto the crank end what if I tighened the tool up and put heat to it. would the heat get to the right place to break the bond in there but not hurt anything? Am I worried about heat on the armature needlessly?
Cycle works suggests a slide hammer on the tool as a last resort but this seems like it would be really bad for the bearings- but you gotta do what you gotta do.
Opinions?

once again, thanks

Ouch! The "tool" was a piece of hardened steel I presume...I really find it hard that it would bend. Usually when it bends, or if you use a tool soft piece of metal, it bends inside the rotor and then there's no way to get it out. Glad that didn't happen to you.

I doubt you can get much heat in the proper area to do any good. As you said, I'd be very concerned about heat getting to areas that it shouldn't.

What about some Aerokroil or PBBlaster? You need to get between the front of the engine case and the rear of the rotor to spray the fluid. If you can do that, maybe a liberal dose would finally work to where it needs to be.

Beyond that, I'd call Vech or Richard at Bench Mark Works for some suggestions. I'm sure they deal with all the time. The taper connection on the front of the crankshaft must have some corrosion on it. Heaven forbid that the PO used some kind of loctite...

I just went through the same issue. I bent a home-made puller, just managed to get it out with great dificulty and then ordered the Cycleworks tool. All I would say is that once you have the puller on very tight, there should be enough compression in the puller steel to "pop" the armature off, if it is going to come. I would agree with Kurt, try some kroil or similar and leave the puller in place for a while and see does it pop off after the lube does it's job. If you are going to try this put a towel or something soft for the armature to fall into. It can really jump off the taper. Best of luck and keep us posted on the outcome.

I think I got lucky, stopping my first attempt just in time. It screwed out with moderate difficulty hopefully without doing damage to the crank and armature threads. I am guessing I am fighting corrosion.
So, I want to get a penetrant behind the armature? Would spraying any into the place the bolt goes help also? If anyone has a photo of the end of the crank and back of an armature so I can visialize how they go together I would be truly appreciated. This a completely a friction fit, no key?

I'm not sure if the R27 rotor/armature is the same as the /5-on rotor, but likely it is. There's no key, just a dry taper fit. This website:

http://www.airheads.org/content/view/194/98/

shows how to make a rotor removal bolt. The graphics give a good idea of where the taper is and the fit up. Given this, it looks like you could flood the area where you put the bolt and it should work its way into the taper. I always thought you could only get to the taper from the very back of the rotor.

Rick has pictures of /5-on rotors on his website:

http://www.motoelekt.com/charging.htm

You can get a sense of the back end of the rotor. I'm not aware of good sources for pictures of R27 electrical parts.

Maybe you could get a hold of Barrington Motor Works and see if they can give you some pictures or ideas on getting at this taper.

Have a look here, photo just added at the bottom of the page. This crank has the cleaned slinger and shows the taper quite clearly. As Kurt says, fill the armature bolt hole with penetrant and try in a day or two!

If you want any specific pictures let me know, while the bike is in pieces!

OK, looks like the fit is about what I imagined. Thanks for the info. I'll flood the bolt hole and let it sit for a few days. Now, if it still won't release I guess I will move on to a slide hammer. Are the bearings, which are replaceable, the only thing I am likely to harm doing this? Anyone have any suggestions on how to attach a slide hammer to the end of the puller tool?
Thanks

Hopefully it wouldn't take much pounding with a slide hammer...I would certainly try small-ish taps. I think what you'll need is a special bolt or hook which can be threaded into the first set of threads of the armature. I don't know the pitch and size of the current armature tool, but a decent metric thread shop could determine that. Buy an extra long version of that, maybe some threaded rod. Bend the end into a hook and then feed the other end into the armature threads. Probably need to be somewhat careful with the slide hammer pounding so you don't ef-up the armature internal threads.

OK-makes sense. It's not an unusual size so I'll make up a rod that can be hooked onto the slide hammer. First I'll give it a few days with PB blaster or acetone/atf cocktail.

it's M8x1.25. I just re-tapped the first few threads!