Topic: Rotor/Alternator Removal

[evitek]

This is relative to a 82 cb650 but it may be applicable to the other fours that use a Regulator Rectifier and a non PM rotor [a rotor with windings].

The end of the rotor hub is threaded internally.  My rotor thread size was M18x1.5 [M18 fine thread] which appears to be common for the old fours in those days.  The end of the crankshaft has an internal thread too -smaller size.
 
Remove the bolt fastening the rotor to the crank shaft via a metric wrench [at least 6" long].  Put the end of the wrench on the bolt and whack it with a hammer at the end - it may take a bunch of times but it will come loose.  Or use an air impact wrench if you have one.

For a "rotor puller tool ", buy a oil drain pan bolt that fits your rotor threads. I bought mine at Autozone for 1.99+tax.  It was 5/8 long - this is the shortest I would recommend.  Prefer a minimum length of 3/4" in but for 2$ I can't complain.

[You can use the rear axel bolt.  This is good if you have a spare.  If you don't and you have access to a bolt - use it as if you screw up your bikes axel threads as some folks have, your bike is grounded until you get another axel.  I thought about using my axel, but as luck would have it, I would end up stripping its threads or I didn't feel like removing it and re-installing it]. 

Lube the end of the drain bolt and the threads with some grease.  Put a steel washer into the hub against the end of the crank such that the end of the bolt will be pushing it against the end of the crankshaft [this is to protect the threads on the end of the crankshaft and act as a spacer since my bolt should have been 3/4" in long].  Thread the 18mm bolt into the end of the rotor securely and verify that when the bolt is tightening up, there is a visible gap between the end of the shaft and the hex flange on the bolt.

Grip the rotor with a oil filter wrench and tighten the bolt up -not all the way -90% of all you got.  The rotor may pop off if your lucky but in most case it will take some patience.  With the plug/bolt tightened/compressed against the end of the shaft, take a hammer and tap on the end of circumference of the rotor near the engine case end.  Rotate the rotor 30 degrees and repeat, over and over.  Tap on the end of the bolt too.  Tighten the bolt some more.  Tap on the rotor.  If it hasn't popped off by now, loosen it up and remove the bolt and smear some more grease on the bolt end and threads and repeat this procedure.  Mine popped off after I reinstalled the bolt the second time when I was tightening it much to my surprise.

Be patient.  If it doesn't pop off, let it sit withe bolt in compression over night.

For 2$, and 1hr and 45min of my time [including the time it took to locate the bolt] - not bad.

[scunny]

the rear axle is the same pitch, on the 650 anyway

[hatchett]

I use an axle bolt for this as well, alot cheaper than buying a "rotor puller".

[754]

The stock tool is turned hand tight, then struck..as most pullers are.  An axle bolt is not made for that..

I used to look at it this way, pay someone to take it off once, or pay for the tool & own it..

You can strike the rotor, but I wont..

[dummkauf]

Someone pointed this out to me on this site

http://www.z1enterprises.com/detail.aspx?ID=2165

$9.52+a few bucks for shipping and you don't destroy your axle bolt.

The 20mm was for my CB750, they also have other sizes too(I know nothing about the 650)
http://www.z1enterprises.com/SearchResult.aspx?All=True&KeyWords=flywheel%20puller

[Tretnine]

I can't get the initial rotor bolt off. I tried a few different things and I even tried to use an impact wrench (the kind you attach a socket to and whack with a hammer) but the damned thing won't budge. Is my only option to use an impact wrench? Is there any way to keep the engine in place so that the rotor won't turn? My buddy works on old beamers and he says he pins the flywheel in place, but I don't want to go breaking anything in there. Last time I needed an impact wrench I went to Lowe's and bought one, used it, then returned it. I'd prefer not to do that, but I don't want to buy an expensive one (considering how often I really need it.) and I don't have a compressor to use a pneumatic one.

Any suggestions?

[tbpmusic]

I can't get the initial rotor bolt off. I tried a few different things and I even tried to use an impact wrench (the kind you attach a socket to and whack with a hammer) but the damned thing won't budge. Is my only option to use an impact wrench? Is there any way to keep the engine in place so that the rotor won't turn? My buddy works on old beamers and he says he pins the flywheel in place, but I don't want to go breaking anything in there. Last time I needed an impact wrench I went to Lowe's and bought one, used it, then returned it. I'd prefer not to do that, but I don't want to buy an expensive one (considering how often I really need it.) and I don't have a compressor to use a pneumatic one.

Any suggestions?

[/i]

If you have the engine off-bike and torn down, many times you can jam something in between the crank's "output gear" and whatever it meshes with and temporarily lock the crank in place. Some guys use a penny, others a piece of wood - I use a chunk of old inner tube.
On the old twins, there's actually a gear on the end of the crank that meashes with a gear on the clutch housing. For the bikes with primary chain drives, it should still be possible to use some variation of this technique - maybe jam the chain itself??
It's never a good idea to actually grab the rotor itself, as you can distort them.

bill2

[dummkauf]

I can't get the initial rotor bolt off. I tried a few different things and I even tried to use an impact wrench (the kind you attach a socket to and whack with a hammer) but the damned thing won't budge. Is my only option to use an impact wrench? Is there any way to keep the engine in place so that the rotor won't turn? My buddy works on old beamers and he says he pins the flywheel in place, but I don't want to go breaking anything in there. Last time I needed an impact wrench I went to Lowe's and bought one, used it, then returned it. I'd prefer not to do that, but I don't want to buy an expensive one (considering how often I really need it.) and I don't have a compressor to use a pneumatic one.

Any suggestions?

This was my solution to the problem, just tie a rope through the rotor to something solid, put a wrench on the bolt, and whack the wrench with a hammer.  It took me several whacks with the hammer but eventually it came out

http://www.thesandmann.com/index.php/motorcycles/cafe-racer-project/34-cafe-racer-project/61-alternator-removal


You didn't mention if the engine was in the bike or not, but the same concept could be used with the engine still in the bike, you'd just have to find something else to tie the rope to, the bike frame should work.

[Tretnine]

interesting idea. I might just give it a shot. If that doesn't work, I'm looking into an impact wrench.Thanks.

[Tretnine]

I did this with the rope. I Tied it to the frame, put my wrench on the bolt, then stood on the wrench. I broke the rope. I redid the rope looping it an extra time and jumped on it again and pop. Thanks!

Edit: To get my rotor off my 1978 550k I needed a fine threaded M16 bolt that I found at a "specialty fasteners" store. It was about $5 and worked like a dream. Check your yellow pages (or google) for a shop in the same vein if you're without a bone fide rotor puller.

[MCRider]

I did this with the rope. I Tied it to the frame, put my wrench on the bolt, then stood on the wrench. I broke the rope. I redid the rope looping it an extra time and jumped on it again and pop. Thanks!

Whatever works is all that counts. But an electric impact is a bit more...elegant?   I had to buy this for some auto suspension work, but once owned nice to have. It took the bolt off without holding the crank in any way, just the quick impact did it.

[Tretnine]

now you're just showing off. I'd love to have an impact wrench... For the time being though, I don't even have a garage. Some day when I have one of those I'll have a pneumatic one, a sandblaster, pressure washer, paint sprayer... (trails off with a far away look in his eye)

I 'rented' an impact wrench from Lowe's one time and I agree, it's a beautiful thing. I'd recommend it it to anyone with a use. The rope I bought from Lowe's however, was 2 orders of magnitude cheaper than the wrench.

[MCRider]

now you're just showing off. I'd love to have an impact wrench... For the time being though, I don't even have a garage. Some day when I have one of those I'll have a pneumatic one, a sandblaster, pressure washer, paint sprayer... (trails off with a far away look in his eye)

I 'rented' an impact wrench from Lowe's one time and I agree, it's a beautiful thing. I'd recommend it it to anyone with a use. The rope I bought from Lowe's however, was 2 orders of magnitude cheaper than the wrench.

A little bit perhaps. But after 50+ years I'm due. at your age i was doing without, and always got by as well. 

If your engine was still in the frame, if one thinks ahead, putting it in a high gear and standing on the brake, or nosing it up to a wall, putting a pipe on the 3/8" drive, will get it off as well. I know.

[dummkauf]

now you're just showing off. I'd love to have an impact wrench... For the time being though, I don't even have a garage. Some day when I have one of those I'll have a pneumatic one, a sandblaster, pressure washer, paint sprayer... (trails off with a far away look in his eye)

I 'rented' an impact wrench from Lowe's one time and I agree, it's a beautiful thing. I'd recommend it it to anyone with a use. The rope I bought from Lowe's however, was 2 orders of magnitude cheaper than the wrench.

Glad to hear it helped!

I'm in the same boat.  No air compressor and no impact gun...would be nice though

[Spanner 1]

Caution!, one quick 'crack ' and my wound rotor ('81 CB750 ) popped off and hit the concrete floor damaging part of the fiber insulator on the rotor face...I'm sure it would not be good for a steel rotor to hit the floor either! Put something soft under to catch it in case it falls when it lets-go of the crank end !