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Discussion Starter #1
I'm replacing the cam chain and guides etc. which requires me to remove the stator and flywheel. I unbolt the nut that threads onto the crank and it comes off like a nut should. I pressed the flywheel off and replaced some gaskets etc and it comes time to put the nut back on.

As I'm trying to thread it on by hand it just wont go. It appears that the crank is fine, but when I take a look at the nut all of the threads are smashed, shaven off, or cut across. I have no idea how this happened, as the nut came off fine, and just sat on my desk while I did the engine work. Not a problem, I'll just buy a new nut. Well my $6 nut came in and I go to thread it on and it wont. After a very close inspection it appears the the first 1 or 2 crank threads are slightly flattened and rolled over.

The main part where I goofed up is trying to force the nut onto the threads to straight them out kind of like a dye. Well obviously the crank is a harder metal and my new nut is toast after trying this. How did this happen and what do I do? The only outlandish thing I can think of doing is cutting a nut or dye in half, putting it over the good threads, clamping it down and threading it off of the crank to straighten those first couple of threads. I called my local shop and haven't heard back as of yet.

-Alex
 

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Can you put it on backwards? I think it has a flange that is supposed to go against the flywheel but if you can thread it on smoothly it should Clem up the threads. Use a bit of lube and don't force it.
 

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Discussion Starter #3
I've tried that with plenty of lube and had no luck. What I don't understand is how the threads on the crank got bent in the first place, and if they were bent before, how did the original nut come off so smoothly, especially since it was so beat up.
 

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What kinda puller did you use to remove the stator?? Sounds almost as if you've mushroomed the threads on the crank ever so slightly.. Ive done this before, best thing is attempt to get a dye started on it and just cut the rolled over threads.. Post up a pic!!!
 

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Discussion Starter #6
I ermmm....made one. But the way I made it, only a 1/4" bolt touched the crank and it stayed seated in the center indention of the crank just like the Yamaha crank puller appears to do. Where can I get a good metric tap and dye set? I've looked before, but have had no luck. Now I have random standard bolts all over my bike ...:rolleyes:

EDIT: pics when I get home. Filing is a last resort.
 

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you can get a die from Snapon -Mac ect
or threw local machine shop supply-
or MSC catalog- Granger --

Look in shop manual they usually give fastener specs-
if not take the nut with you to match with die

I dont think the end of crank shaft is hardened
so it is possible that you could use a Castle Nut
threaded on Backwards to clean up if the threads are not to messed up-

If you try a thread file practice on something else--
they can be a little tricky--

what ever you do dont make it worse- it can get expensive Quickly --Jay--
 

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Discussion Starter #8
Ah, I just brought home a MSC book from work. Obviously they would have them.

Here are some pictures. I had a hard time taking the pictures and making them still visible.

Here is the puller:


This is the only part that touches the crank, you can see how the bolt presses in there:


Threads, you can see towards the top where it looks like they mess up:


old nut:



new nut:
 

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Is that a pic of the threads now? They look to be easily salvageable. What's the size and pitch?? It's been a long time since I've been inside a 400, maybe I still have my shop manu laying around somewhere. I bought a very large set of taps and dies at Sears many moons ago. Ace Hardware usually has some random taps and die individually hanging on the shelf. Neither of the above are high quality machinist tools but will work very well for the home mechanic. Too bad your not close.

Doubt you did any harm with the puller. Motion Pro sells a rather inexpensive one for most bikes as well.
 

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NEVER use a tapered tipped bolt on the end of your puller! Thats what caused this, I've done it too, on old Yam streetbike though. The pointed tip tried to spread the hole in the crank end, in a worst case you can actually split the crank end. That why most universal pullers will have hard flat tips you can interchange. You're lucky the flywheel came off easy, or it would have been much worse.
 

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Get another new nut

a THREAD file (looks like a knife) or even a 1/4 round file using the edge will clean up those threads easily. Take your time and keep trying the nut till it goes. If you file the first thread totally away on the crank it won't hurt a thing. All is not lost. Patients is the answer to your problem.

Nice pics they helped.

David R
30 year mechanic
 

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Discussion Starter #12
I had to apply a decent amount of strength to get the flywheel off, that's what tapered the bolt. The oem one appears to have a tapered bolt as well, that's why I chose to use a bolt the size that I did. I was affraid that if I put a flat piece of metal in between the bolt and the crank, I would compress the threads but we see where that got me, though I still dont see how I rounded off that first thread.

Looking at the threaded portion of the crank, it looks like the end 1.2in" section is fatter than the rest, but when I put a straight edge against it, they all line up flat against it. I think I'll let a shop take care of this one, but I have a feeling I will have more patience than the shop mechanic. I'm afraid he'll mess it up and just say it wasn't salvageable...:anim_peep:
 

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Damn that sucks Alex, hate to hear that man. I think I paid $50 for my puller, and yeah, that seems pricey. But, I had zero headaches at all with it, and knew that my crank and shiny new flywheel were safe with it. For me, that was worth the investment alone. Plus, I hate having to bum tools, especially expensive ones. Good luck getting it worked out, and keep us posted.
 

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Damn that sucks Alex, hate to hear that man. I think I paid $50 for my puller, and yeah, that seems pricey. But, I had zero headaches at all with it, and knew that my crank and shiny new flywheel were safe with it. For me, that was worth the investment alone. Plus, I hate having to bum tools, especially expensive ones. Good luck getting it worked out, and keep us posted.
I agree with that philosophy, I've messed up more shit and spent more $$$ fixing stuff from using "jerry rigged" made up myself, tools than what Ive spent in just buying the right pullers & splitters etc.. www.Pitposse.com has an AWESOME!! selection of pullers at a VERY reasonable price. Last rotor puller, I bought for a Cr250 I rebuilt was on sale cost me $9.95 + shipping

Id get a Mic and check the overall OD diameter of the threads, maybe it's just me but the end of that shaft does somewhat appear to have mushroomed a little. Thats the weakest part of the crank and a smaller bolt getting tensioned in there will do that almost everytime.. Like others have said Id try a thread file 1st to clean it up enough too try and run a Die over it.
 

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Based on your picture(s), it doesn't look like the crank is too buggered up, just a few of the initial threads got a little banjaxed. I would just pick up a die in the correct diameter & pitch, and clean those first couple threads up, all good!

Try this:

http://www.mcmaster.com/#dies/=9iq0ea

I don't know what size that is, but it's probably only a $15-$25 part.
 

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Discussion Starter #16
Thanks guys, I'm going to see if I can't borrow some dyes and thread file from work if we have them. If not, I'll be buy a set.
 

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I've fixed a few cranks like this with a file and a little bit of patience. The only thing that scares me about using a die is the potential of cutting the threads out of phase and ruining the crank. If you choose to use a die, just be damned sure that you're not cutting new threads over the tops of your old threads. Good luck with it.
 

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If you go the using a Die - buy Good quality one-US -Japanese -English- German-
- not Chinese junk--

Also you can get Adjustable Dies --using a Adjustable die you can
cut threads of differing thread Fullness --
The fuller the thread the tighter and stronger the fit-

Some Cap bolts- Allen screws have a Very full thread --
Maybe to full to fit in stock threaded holes-

Usually these bolts are Hardened but with a good quality
adjustable die you can reduce the Fullness of the thread -- some --

Always use a Tapping Fluid when cutting threads-
Its not regular motor oil- WD40 or anything like that-

Tapping fluid has some type of sulfur compound in it
and it makes a Huge difference -- cost $3 or so -

Always turn Die -Tap 1/3rd turn IN then back it off 1/2 turn
doing this brakes the chip and gives better thread -
repeat until threading is complete --Jay--
 

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Discussion Starter #19
Thank you for all of the suggestions. My work was of no help, but I'm currently in a shop class right now so I'll ask my teacher to see if he can't get me access to the proper tools.
 

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for sure just run a dye over that puppy its not gonna take much just off the end where the nuts not really holding threads anyway.. and get a new nut, it will be fine
 
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