Topic: Am I and my rotor/crankshft screwed?

[Lazerviking]

I'm in the process of putting my cb750 k7 engine back together. I just sealed up the cases and the side covers and was cleaning and reinstalling the pistons/rings when I noticed that I had forgotten to re-install the large bolt that holds the rotor onto the end of the crankshaft. No big deal right? So I open the alternator cover and go to thread it in and it just won't thread. I'm being patient and not mashing it in there in order to prevent damaging the threads when I notice that it looks as though there is a little metal lip right before the threads  begin in the crankshaft.

Here's where my brain grapes start juicing...

When I first tore my engine down I was trying to pull the rotor off with a pulling tool(i posted picture of it) but never succeeded in getting it off because it was on the crankshaft so tightly. Either way I am figuring that in my attempts to pull it off I either smashed the first threads on the crankshaft or curled the end/edge of it, thus preventing me from being able to thread the rotor bolt in now.

What can I do to correct this? Is there an oil passage in the crankshaft that leads to the cases if I were to attempt to dremel the metal lip off while its all installed? Can I re-tap the shaft and use a different bolt? Is this bolt even necessary? Considering how f****** tight the rotor is on the shaft already?

I'm feeling so close to finally having the engine all buttoned up that the thought of the crankshaft now being totaled is really really really discouraging. And having to open up the cases again makes me extremely frustrated thinking about. But I need to remedy this situation.

Please bestow me with all of your wisdom.

Pictures;
1) looking down the rotor
2)close up of the rotor hole and an arrow pointing at the curled metal lip preventing my bolt from threading.
3)rotor bolt
4)puller tool I believe may have cause the curled metal lip

[Jerry Rxman Griffin aka MuthaF'er]

Use the threaded in type puller (actually pushes) and an air gun on it.

Looks like the rotor is somehow stuck part of the way on/off? Can't really make out much from your pictures.

[Lazerviking]

Hey Jerry, so you think air gunning the threaded type rotor puller will push me through the metal lip that's formed? Do you think that will push the metal shards from the curled lip into the crankshaft threads and damage them?

I can try and put up other pictures but I'm not sure how much more detail I can get. The picture with the arrow is showing the curled lip that is preventing the rotor bolt from threading into the crankshaft. The threads are right behind the lip and are a slightly larger diameter hence why the bolt can't find the threads.

Not sure if I have clarified anything.

[Jerry Rxman Griffin aka MuthaF'er]

I can not envision a metal lip?? How could that happen and from which part?

If something is blocking the threads you may need to run a thread cutter perhaps?

[brandEn]

I would use the rotor puller that is a bolt like Jerry said. I just got one off of Amazon made by Motion Pro for under $10 shipped with my Prime membership. Use an air driven impact driver and you will have that rotor off in 2 seconds. Then address the threads in the crank with the proper tap and maybe get a new rotor bolt as well. I bet those threads just need to get chased with a tap and you will be good to go.


Motion Pro Rotor Puller from Amazon!

[Lazerviking]

I'm thinking this;
The puller tool I used in attempt to get the rotor off of the crankshaft works by inserting the round threaded center piece into the hole where the rotor bolt is meant to thread, then the 3 outer arms that pivot hold onto the rotor itself, and then I twist the round center piece until it is tight up in the rotor hole(where the rotor and the crankshaft meet and the rotor bolt threads in). After it's hand tightened I then continued turning the round threaded center piece of the puller tool with a wrench in an attempt to pull the rotor off by using the force of the puller tool on the rotor that is pushing against the end of the crankshaft.

I'm thinking that when I wrenched on the puller tool, the end that was pushing against the crankshaft has a little taper on it and squished the end of the crankshaft, leaving a lip of metal on the inside of it where the rotor bolt is meant to thread in.

I drew a primitive drawing if that helps at all.

Let me know if I still am sucking at explaining this. Haha.

[Lazerviking]

Thanks brandEn, I will be needing one of those. Getting the rotor off will make everything sooo much simpler.

[brandEn]

I think the front axle can also be used if you want to try that. I believe it is the same threads...

[05c50]

The three jaw puller is the wrong tool for the job, it could distort the rotor when pressure is applied, but that's water under the bridge now. I've used the rear axle to pull off the rotor, but since you're working to repair a damaged part, I would highly recommend using the right tool as suggested and then the threads can be repaired with a thread file or tap.

By the way, many of the three jaw pullers like the one you used, have a removable insert that goes in the end that will prevent the damage from happening. Too bad yours didn't have this feature.

............Paul

[Lazerviking]

Got that rotor extractor coming in the mail, should be here tuesday, I'll keep you posted on my progress.
Thanks guys. Oh and Paul, my three jawed puller didn't come with that removable insert. Oh the hours of frustration that little piece would have saved me. 

[754]

It's called a shaft saver I think, and go puller makers have it available.
 Was up some cloth or paper towel push it into the crank a good inch, now start filing with round file, to remove the damage you caused..
 Might be able to use a diegrinder to clean it up,  but tape everything off so nothing goes into the engine.

[Lazerviking]

Thanks for the tip. I was unsure wether that hollow threaded portion of the crankshaft went into the engine, but now I know!

[martin99]

I think you could use a round file to clean up the lip you've created. I also think you have a problem with the bolt itself though - unless it's just the way the picture is taken I can't see where the thread starts, and I'm wondering if you've compressed it while trying to get it to go in. You'l need to run a die over that to restore it IMO or even with the lip repaired the bolt will probably just spin and not screw in.

[Lazerviking]

I think you could use a round file to clean up the lip you've created. I also think you have a problem with the bolt itself though - unless it's just the way the picture is taken I can't see where the thread starts, and I'm wondering if you've compressed it while trying to get it to go in. You'l need to run a die over that to restore it IMO or even with the lip repaired the bolt will probably just spin and not screw in.

I was being careful when I was trying to thread in the rotor bolt so I think it should be okay. But I'll find out when I get my metal lip issue cleaned up Thanks for the tip, one of the many things I've learned during this process is to not try and force things. That never ends up well.

[MiGhost]

What has happened is the narrowed shaft of the puller that you used slid inside the threads as you tried to pull the rotor. Flattening, and pushing the threads into a burr. That style puller is used only on solid shafts, or with a bolt in the internal threads

To correct the damage you need to remove the burr created by the puller before you reestablish the threads. Otherwise you risk cutting cross threads with the tap. You can do this by carefully drilling the burr using a fresh new drill bit. You are only trying to cut the burr. Not remove a serious amount of metal. Filing, or grinding the burr will also weaken the threads behind the burr.

Once the burr is cut. A tap should catch the existing threads. Once the tap catches, and starts moving in without cutting. Run the tap completely in to clean and chase the remaining threads.

The bolt does look to have some minor damage to the first thread. This should clean up easily with the correct die, or a quick dressing on a grinder. Once again, You are only trying to clean up the damage. Not remove a bunch of material.

   

[Lazerviking]

Using the proper tools sure does make things easier. I got the proper rotor extractor and got the rotor off without a problem(finally). I jammed a rag into the shaft to prevent anything from getting into the case and then proceeded to dremel off the raised metal lip I had created. It came off pretty nicely, thankfully. I ended up having to order a tap off the internet in order to allow the crank to receive the bolt again, turned out to be 18mmx1.0. Got it tapped and installed the rotor and bolt again. Bada bing bada boom!!! Thanks for all the help fellas, you made my life a lot easier.

[Jerry Rxman Griffin aka MuthaF'er]

Torque that #$%* down to 70 ft lbs or it will spin loose.

[Ravie]

Dude!  I'd been following this thread when you first posted. Glad you got it figured out. I hate when stupid crap like that happens to me.

[Lazerviking]

Dude!  I'd been following this thread when you first posted. Glad you got it figured out. I hate when stupid crap like that happens to me.

Thanks Ravie, this is my first bike and every step of the way has thrown me a hurdle, luckily none have stopped me yet!