Topic: Restoring my k0 cb750

[754]

 Avoid that method..there are internal pulling threads in the rotor for a reason..

[Cragdog]

After you torqued it up, strike it with a hammer.  Hat is why I hate the axle idea.
  Zero runout on crank, well maybe a thou or two.
Now that rotor is off use an elastic or something to hold a pencil or straw, and see if you have visible runout.

Okay so, I still am waiting on my dial indicator, BUT it has become very clear to me that there is definitely runout on the crankshaft, or at least on the end that got hit. I stared dead on at the center of it and had my gf rotate the crank, I could easily see a "wobble" in the crank with my naked eyes so that's that. Where does that leave me?
Couple of Questions:
Will I need to replace the whole crankshaft? and if so, is this a good deal: http://www.ebay.com/itm/1970-CB750K0-CB750-K0-CB-750K0-Crankshaft-Crank-Shaft-/151105031007?pt=Motorcycles_Parts_Accessories&hash=item232e8fcb5f&vxp=mtr
What about my rotor/stator/field coil? Is it a bad idea to try and reuse these if they have scratches/blemishes?

Feeling a little bummed out at this point, I was really hoping I'd just have to replace the rotor... 

Thanks for any comments or suggestions.

[754]

GET IT GREAT PRICE FOR early crank.. Dont be bummed its not that pricey to fix, but look around the case where the crank exits for cracks., before you buy the crank. Good Luck..

[Cragdog]

Thanks 754, I'll have to wait until I get home from work to look at the exit point again, but when I was looking at it last night I didn't notice any cracks. Looked like there was a washer or bearing it went through at the case opening which hopefully saved my cases. Everything INSIDE the cases connecting to the crankshaft, cam lobes and connecting rods appear to move freely and without sway, so I'm hoping I can just drop in the new crankshaft and seal her all back up.

Since I have to open up the whole motor now at this point, is there any relatively inexpensive upgrades I should consider to the engine anyone would suggest? I have heard new chain tensioner and hd chain are a good start, what else should I be looking at while I'm in there?
Thanks for all your help and support guys! Great forum, great community, great motorcycles.

[754]

You didnt have to open it up. If you took cam out, side covers off , top case bolt, flipped it over, took rest of bolts out.. You would be ready for crank swap..

[Cragdog]

You didnt have to open it up. If you took cam out, side covers off , top case bolt, flipped it over, took rest of bolts out.. You would be ready for crank swap..

All with the top end still attached?!?! 

[754]

Just undo the cam chain by taking cam out or cut chain

[Cragdog]

Let's see if this video will post. Crank is shot unfortunately...

http://youtu.be/pvtvEo6e-XQ

[scottly]

You didnt have to open it up. If you took cam out, side covers off , top case bolt, flipped it over, took rest of bolts out.. You would be ready for crank swap..

All with the top end still attached?!?! 

That's what I was trying to tell you earlier.

Yeah the crank is toast; you've got about .055" of runout.

[Cragdog]

You didnt have to open it up. If you took cam out, side covers off , top case bolt, flipped it over, took rest of bolts out.. You would be ready for crank swap..

All with the top end still attached?!?! 

That's what I was trying to tell you earlier.

Yeah the crank is toast; you've got about .055" of runout.

Ha! Damn... Oh well this is my first time opening up a motor so excuse my greenness 
I'll be waiting for that crank to show up until I can move forward with this. Thanks everyone for all your help here. I'm looking forward to getting this resolved!

[Cragdog]

So the replacement crankshaft came off the brown truck yesterday. Couple of wear through spots on the box, hopefully this crank is in good enough shape to replace the old one. The seller couldn't tell me if it had runout, but it was cheap so I just grabbed it and crossed my fingers..

Tonight is Halloween so the gf will probably make me carve pumpkins and hand out candy to all the lil kids in the neighborhood so I might not get to touch the cb until this weekend.

What do I need to be careful about with replacing the crankshaft? Am I going to need to buy other parts too or is this just a swap and drop fix? Thanks to all you more knowledgeable guys on this for your input, I GREATLY appreciate the help. 

[Cragdog]

I am stuck at a nut. A locknut to be exact, the one holding the clutch basket in place and I don't have the tool to remove it and can't find one at any of my local hardware shops.. Notice the 90 degree apart notches around the nut. Each of the salespeople I asked looked at me like I was crazy because they didn't understand what I was talking about. 


On a side note, making some progress on my other project:


If anyone is still viewing this thread, I need some answers about the crankshaft swap as far as what to expect and whether or not I need to purchase additional parts to complete the job. I'd appreciate any and all input, thanks guys.

[Greggo]

You need to look into plastigauging the bearings..

[Cragdog]

It's been really slow going with this motor, lack of time and money and experience has made this a lengthy process and I've been getting a little frustrated..
I did finally get the locknut removal tool, but haven't been able to figure out why the clutch assembly if freely rotating making it impossible to loosen the locknut. Even if I keep the front sprocket stationary, the clutch basket still spins. I did this all according to the climber manual and it hasn't mentioned anything about this. I have already removed the shifter assembly and I'm assuming I last had the tranny in neutral, should I reassemble it and get it into first? Would that lock up the clutch so I could remove the locknut? Thanks for the help, this website has been an awesome resource and filled with good people left and right. I really just want to be riding this bike again..

[754]

Usually the top end is on and gives it resistance, may need to use an impact gun , or pull the shaft out when you split the cases. Then hold in vise with soft jaws and remove locknut.

 You will need to go over bearing selection and  fitting in the manual, to see which bearings you have to order, and where to look for the code on the crank. This requires a lot of attention, and you may need to study it for a while.

[Cragdog]

Usually the top end is on and gives it resistance, may need to use an impact gun , or pull the shaft out when you split the cases. Then hold in vise with soft jaws and remove locknut.

 You will need to go over bearing selection and  fitting in the manual, to see which bearings you have to order, and where to look for the code on the crank. This requires a lot of attention, and you may need to study it for a while.

I'm worried about using the impact gun spinning the clutch fast as f*%k, a legitimate concern? Or an over-cautious greenhorn?

As far as plastigauging and bearing measurement, yes I have a lot to learn and absorb before completeing that task. Currently the only manual I have is the Clymer. How reliable is this for that application? I haven't yet read through that section, but I know Clymer for my Suzuki has all kinds of god-awful mistakes.. Is there any place with really good documentation of this procedure you would recommend? I know Hondaman's book has the info, but I haven't got around to ordering a copy. If anyone knows of a good place for me to study up I'd really appreciate it.


Also, this is bad I'm guessing.. Not sure where these shavings came from as my cylinders didn't look gouged up, could be pieces from the case/rotor when I hit the bench.. but would they have traveled that far into the motor without it running?? ughh..

[edwardmorris]

I know Hondaman's book has the info, but I haven't got around to ordering a copy. If anyone knows of a good place for me to study up I'd really appreciate it.

Hondaman's book is a must along with the factory manual available on these forums. Hondaman's book has outstanding theory on how things work and why they work that way, with good hands on info on critical tasks. The factory manual has rest of the obvious stuff. Knowing how things work the way they do, at least for me, has given a much better perspective on my own build and how to approach things.

[754]

You may have to slip crank back in,or pull clutch and shaft out to take chains off .maybe you can hold clutch shaft in soft jaws and use the impact.
I hot my bearing info from a clymer manual..the mistake I found in my Clymer, eas a wiring diagram..cost me a bit of money and A LOT of GRIEF..
 Not sure about the chips, but its apart now anyway..inspect everything.

[Cragdog]

A little more progress here and there. I wish I had the experience and all the tools available to get this done more quickly, but this is a learning experience for me and trying to take my time doing it the right way.
I got the clutch off using my impact gun and a vice grip on the basket.


Had to wait a couple weeks to get this rediculous locknut remover.


The cases are like fused together, I'm finding it near impossible to take them apart. I have removed all the bolts according to the manual, but still no luck. If anyone has any ideas I would seriously appreciate it. I've tried using a rubber mallet on certain areas but it's not giving in at all! 





Hope to be posting more once I get the cases spilt. I am definitely going to need some help with figuring out bearing selection and plastigauge process ect. for the crank swap.
Thanks for looking!

[Greggo]

I see a bolt still attached next to the neutral switch.  My sandcast cases required a piece of drift wood, and a BFH (big fuking hammer) to get them apart yesterday.

[edwardmorris]

Where did you acquire this lock nut remover from? If you don't mind sharing..

[SOHC4 Cafe Racer Fan]

Where did you acquire this lock nut remover from? If you don't mind sharing..

Looks like the one Cycle X sells.

[754]

Check on top of case, by starter cavity and rear of case,there is a few that are easy to miss.
Remember when tapping the cases, there are dowels to prevent SIDE movement, you have to knock them apart carefully without damaging.. Using wood or plastic drift helps.

In your case hang onto starter hole with your hand and give crank snout a rap...nothing to lose.. But i suspect something may be holding it.

[Cragdog]

Where did you acquire this lock nut remover from? If you don't mind sharing..

Looks like the one Cycle X sells.

I got lucky and found it pretty cheap on eBay. The seller has 10 left available if anyone else is in need. http://www.ebay.com/itm/400603467715?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

[Cragdog]

What do i need to prepare myself to buy for measuring the crankshaft bearing clearances? Plastigauge? But what type and clearance range? What exactly is the purpose of measureing these clearances? Excuse my noobness  , i have never done precision work like this on a motor before. But is it to determine what size bearings I need to buy for the new crankshaft? Thanks!