The Free CB750 - Project Zoidberg

Sonreir said:
I knew drill presses were "better" than handheld drills, but it really surprised me how much easier it was to start drilling out the broken bolt. 5 minutes.
Click to expand...

Drill presses rule. Especially when you want to make your brake rotors look sweet.
 
OK... I give up. What's the secret to splitting the cases?

It feels like it's loose enough to come apart, but something near the rotor is catching. It separates about half of an inch, but then it feels like the crank is trying to come with the case. Same situation when I flip them and try from the other side.
 
I bet there is a circlip somewhere inside that you need special tools for. Or something equally annoying.

Can't wait to see this come to geather.
 
Shouldn't be any circlips. If you've taken out all the bolts top and bottom it should come apart freely. Double check the 6mm bolts towards the sprocket. If you're starting the separation from the rear, and it's getting stuck part way open, there might be a bolt right at hte front that still needs to come out. Otherwise, the cases should separate without any issues - there should be nothing inside that catches.
 
Well the cases are moving apart from one another at least .5" all around. Something at the crank/rotor is catching.
 
Not sure on the 750 but my 400 HA a bit inside the oil pan that's pretty easy to miss....
 
Sonreir said:
Well the cases are moving apart from one another at least .5" all around. Something at the crank/rotor is catching.
Click to expand...
The DOHC's are a bit different than the SOHC's I've worked on, in that the DOHC's need to have the oil pump and the rotor removed before you separate the cases. Other than that, not sure what could be catching.
 
Does say in the shop manual to remove rotor. But I cant see what on the rotor would stop it coming apart. There is one bolt inside the oil sump.
 
notlob said:
Does say in the shop manual to remove rotor. But I cant see what on the rotor would stop it coming apart.
Click to expand...
Yeah - neither can I. I've looked through the manual as well as the parts microfiche and can't see anything that would prohibit removal.
 
STILL no luck with the rotor. I'm gonna pick up a rotor puller some time next week. The swingarm seems to have the correct size thread, but either the pitch is off, the threads aren't long enough, or the bolt is too long to get the torque properly applied...

In the mean time, I occupied myself by mounting the Husky fender to the lower triple using some U bolts.

374399_10151554354050159_117412281_n.jpg
 
Sonreir said:
STILL no luck with the rotor. I'm gonna pick up a rotor puller some time next week. The swingarm seems to have the correct size thread, but either the pitch is off, the threads aren't long enough, or the bolt is too long to get the torque properly applied...
Click to expand...

Either the swing arm or rear wheel spindle should fit (I cant remember without checking) But unless you can lock the motor up you'll need a air impact wrench.
 
The swingarm seems to have the correct size thread, but either the pitch is off,
the threads aren't long enough, or the bolt is too long to get the torque
properly applied...
Click to expand...

Either the swing arm or rear wheel spindle should fit (I cant remember without
checking) But unless you can lock the motor up you'll need a air impact wrench.
Click to expand...
Yep, pretty sure it's the rear axle that's the same. Are you out of threads on the bolt? as in it bottoms out the threads? Screw your bolt in, if you still have threads, mark how deep it is on the bolt. Then remove it and stick something in the hole (screwdriver) and mark how deep the hole is, then compare the two. Or stick a small piece of modeling clay onto the end of the bolt or the shaft and screw the bolt in and see if it compresses the clay flat... That will tell you is you are contacting the shaft with the bolt or not.
Your need the "shock" of an impact to break it loose. I am NOT suggesting strike the rotor! But if you've determined above that the bolt is contacting the shaft, and you do have threads left. Tighten the bolt and strike the head of the bolt with a hammer while tourqueing on it. Just a good sharp "whack" square on the head should do the trick. Not enough to distort the bolt head, just the shock of the impact while torqueing tight. It would even be better if you can do it with a brass mallet if you have one... or a hard wood block between the two if you can get someone to lend a hand that trusts you with a hammer or vice -versa. ;)
 
I cant believe you guys cut the bearing races! Mine were totally garbage, but I tapped them off with a hammer and some gratuitous force in about 20 minutes. I guess I'm using a primitive toolset.

On the rotor:
This is so odd. I'm still stuck at the same place in my DOHC, waiting to open the engine, and the air impact is increasingly the only option. Looks like both of us are gonna be putting towels down in the commuter cars to get to the air tools. Other than that, has the engine teardown been pretty parallel with the FSM? I got my gaskets last week, and I'm worried I'm not ready for it yet.

And I also believe the rear axle is a direct fit to the INSIDE threads of the rotor bolt, which are still not initially exposed due to the resistance of the rotor to removal, correct?

Subscribed instantly. Welcome to the DOHC club, where we scratch our heads as much as we ride these bikes.

1981 CB750K (a bunch of parts in boxes)
 
My neighbor has a mill and he was happy to put it to use removing the fender mounts from my fork lowers.

601561_10151558465850159_1491520129_n.jpg


10 minutes of wet sanding with 120 grit followed by another 10 minutes with 220 grit remove the high points left by the milling process.
598935_10151558465810159_198325084_n.jpg


Three more to go...
 
Aren't the fender mounts also the fork brace mounts??

Are you planning on an after market Brace ??


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Cool. I always thought you were smart :)


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