Topic: CB750 Motor rebuild... for dummies

[Patrick]

I use a bolt. Be careful to match the thread.

Patrick

[Terry in Australia]

I've got a proper puller mate, but I'm told a rear axle will work. Cheers, Terry.

[Roscoe]

Thanks guys,
I'll try a bolt first hopefully with the right thread otherwise I'll have to get the right thing. Cheers, Roscoe

[Terry in Australia]

No worries mate, the thread size is 20mm x 1.5. 

[Roscoe]

Thanks Terry, I'll put a photo on to show you the condition it was in when I got the bike when I figure how to put a picture on here that is.. I have a long road ahead.
Cheers, Roscoe

[Patrick]

Screw the bolt in until it is flush with the end of the crankshaft and then bump it with an impact driver. The rotor will pop right off.

[754]

Stock puller is tommy bar type.. no wrench fits on ..probably for a reason.

My experience for pulling parts of on a taper is usually  snug the puller up as much as you can.. in the case of the Honda factory tool, that would be by hand.. then strike the end, it will usually fall off.

Dont know what the factory one cost, but I think it was reasonable way back..should be pics of it in the manuals..

[Roscoe]

Thanks again guys. I've just tried to undo the bolt that holds the rotor one and can't budge it. Any idea's I think I'll need to get a big long bar to slide over the socket bar to get some leverage

[Terry in Australia]

It can be a bastaard of a job mate, I just about destroyed my puller in the process, my rotor had rusted onto the end of the crank, (came from the northern NSW beaches) and I had to use a massive 4 claw bearing puller and my oxy/acetylene torch to get it off. (that was on an F2 as well, hmmmnnnn..............) My other ones have popped off with no trouble at all. Cheers, Terry.

[paulages]

i have an axle bolt that has a 23mm head on it-- thought it was from a 550, but i know most of 'em have the round end you have to put a screwdriver through to hold. maybe the one i have is from a 350 twin. anyway, an impact wrench on that takes the stator right off.

[Roscoe]

Thanks guys. I have finally found out how to put a photo on here. This is the bike as I got it. I have stripped it down completely now.
Cheers
Ross

[Terry in Australia]

Yeah Ross, I know the feeling, we should start a "before" thread, for those of us that haven't gotten to the "after" stage yet.

My F2 (bought on EBay for 500 bucks) was the biggest heap of shiite that I've ever brought back from the dead, all I ended up using was the bare frame, wheels and engine (after I totally rebuilt it) even the wiring loom was stuffed, it'd been in a fire at one stage, and all the wiring was melted, what a bloody nightmare! Still, it looks nice now. Cheers, Terry.   

[Roscoe]

Hi Terry, You're right about a bloody mess. I have managed to get items from ebay USA and even a couple off ebay Australia including a new wiring harness. I've still got to find a tank, and seat. I should then have most of the major items. I had the frame sand blasted and powder coated. It looks like brand new so Í'm looking forward to getting to Oz so I can start the real task of trying to put it back together. The engine is going to be the major though I think.
It took me a while to actually find out what model it was. It had been registered as a 1985 CB750 but it obviously wasn't. It had a Suzuki tank, seat and fairing attached. Here's a couple of pic's showing where I'm at. Cheers, Roscoe.

[Terry in Australia]

No worries Ross, it looks like it was pulled out of a drain, ha ha! Interesting where they mounted the vin plate, has that been moved, or is it a NZ thing? Normally they're mounted on the steering head? Cheers, Terry.

[dagersh]

Terry,

My General Export '76 K has the vin plate mounted there as well.  However, its not a plate, but rather a sticker.

Very strange....

Gersh

[Roscoe]

Morning guys. The vin plate is original and as far as I can see has always been there. It is metal. See attached


Cheers
Roscoe

[dagersh]

Very interesting!  I wish I knew what mine was all about.

Gersh

[Jerry Rxman Griffin aka MuthaF'er]

Hi Terry, Thanks for that. We're moving to the Sunshine Coast, Mooloolaba as soon as our house sells. I'll keep in touch with you. Cheers, Roscoe

Geez Roscoe, do you know what you're getting yourself into?! No, not with the bike! You haven't heard of the infamous Terry The Sheep Shagger yet?! 

[Roscoe]

Yea, It took me a while to find out the model CB750G but finally found out it is definately an F2

[Roscoe]

Hi Terry, Thanks for that. We're moving to the Sunshine Coast, Mooloolaba as soon as our house sells. I'll keep in touch with you. Cheers, Roscoe

Geez Roscoe, do you know what you're getting yourself into?! No, not with the bike! You haven't heard of the infamous Terry The Sheep Shagger yet?! 

Sounds like a very knowledgeable guy. Especially for an Australian. But I guess soon I'll be one as well. Some friends of mine have said that when I leave NZ I'll be doubling the IQ of both countries.

[Kevin D]

I fiddled with the clutch a little bit today. I drilled extra holes in the hub for better oiling. It came with 10, I added 8 more. The Barnett springs I put in last year took care of most, but not all of the clutch slip. I sanded the friction plate faces just a little bit to knock the glaze off. They are original and still measure 0.135", well above the service limit. I hope this will take care of the rest of the slip and not cause any additional problems. I'm not a drag racer or ton-runner, just an occasional gear-banger redline visitor .

[mal]

Yet another question for the experienced rebuilders out there.

I have measured the bore diameters and piston diameters, and they are within the wear limits that are specified in my shop manual. On that basis, I was hoping to be able to reuse the existing pistons, piston pins etc.

However, when I measured the ring end gaps, they are way over the maximum allowable limit. My manual says the maximum end gap is 0.7mm, but some of my rings are double that. I know its a dumb question, but I need to ask it. If I buy a standard ring set, will those end gaps come down to within tolerance?

I am assuming that since the bores are within tolerance, its just the rings that have worn and expanded. Has anyone any ided of just how far they will wear?

Never having replaced rings before, Im not sure if you have to grind them down to the specified end gap, or should they just be used as shipped?

Thanks
Mal

[bryanj]

If you get Honda rings they will noy need gapping

[legendary]

Guys,
         Really intended to focus on the build with this thread. But I haven't posted any progress in a while and I felt that everyone following this deserved a progress update.

    My "non-CB750 life" interrupted my build-  I have to sell my home and relocate for my career. In order to keep the parts tidy I am re-assembling the motor, hand-tight. Then I am moving my parts to Mom & Dads barn until I can get settled and get back to it. Realtor tells me that cleaning the garage could help the resale value- 
 
    Silver lining is that anywhere I move to will have more CB people than my current area.

    I am happy to see that enough people are chiming in to keep the thread alive...I will be keeping an eye on it.

    Sincere thanks for all the help I got. It will not be wasted-I shall return!   Steve

[Terry in Australia]

Yet another question for the experienced rebuilders out there.

I have measured the bore diameters and piston diameters, and they are within the wear limits that are specified in my shop manual. On that basis, I was hoping to be able to reuse the existing pistons, piston pins etc.

However, when I measured the ring end gaps, they are way over the maximum allowable limit. My manual says the maximum end gap is 0.7mm, but some of my rings are double that. I know its a dumb question, but I need to ask it. If I buy a standard ring set, will those end gaps come down to within tolerance?

I am assuming that since the bores are within tolerance, its just the rings that have worn and expanded. Has anyone any ided of just how far they will wear?

Never having replaced rings before, Im not sure if you have to grind them down to the specified end gap, or should they just be used as shipped?

Thanks
Mal

What Bryan said Mal, "Noy" is English for "Not", ha ha! (sorry Bryan) If your pistons aren't damaged, get some new rings, run a hone thru the cylinders, and it'll be right to go! Cheers, Terry.