Topic: CB750 Motor rebuild... for dummies

[andy750]

Hey Steve, dont forget the 2 screws under the breather cover (the little triangle cover on top of the engine in the center) - take cover off and remove the 2 screws before removing the valve cover.

Looking good,
Andy

[legendary]

Answers ;

jsaab2748-  "Good Screwdrivers" are in the eyes of the beholder. I stood in SEARS today and ultimately         
                  decided that I probably wasn't looking at any "Good Screwdrivers".  Whose do you like?

Terry - Your parts list made me smile. That is the kind of help I need....Specific!
          Gasket set- is no where near as useful as "Get the Cycle X gasket set!" Thank you!   

Gordon- Probably good advice on the studs... but I am going to wait until the engine is apart that far and
             weigh the options. If I replace them we are going to chat a lot more!  If I needed that I would be
             willing to send that job out.

754-  There are several decent machine shops near me- any idea what a tapered bore check should cost?
         Valve job?  I'd like to cross that bridge when I get to it. When I post a pic showing the valves point them out.
          Yes- I am serious!

jevfro- Follow along and try to learn from our mistakes... that is what this thread is here for. If you need a
         specific pic let me know.

All- Great discussion on removing studs- and I will refer back to it. I am soaking this up like a sponge.
      I am focusing on what is on my plate at the moment... I can see there are differing schools of thought
      hopefully the engines internals will make it clear which way we need to go.

[Patrick]

A tool I find useful during teardowns is a rubber mallet or dead blow hammer. It can be real helpful to break loose old gaskets.

Patrick

[jsaab2748]

Once you get the valve cover off, things will get interesting. Just as a suggestion, keep everything organized as sub assemblies in a way that illustrates how all the parts go together when you are ready to re assemble. Mark things as right/left or front /rear if it helps. Keep associated bolts in thier respective holes of sub assemblies that you have taken out along the way. When it's time to clean sub assemblies, work with one thing at a time and set it back aside in order. It keeps things from getting lost and is a lot easier than trying to figure out which bolt goes where, while sorting thru a coffee can full of bolts. You'll have your own style I'm sure,
I only suggest this cause' I'm remembering my first 750 top end
rebuild in '74 when I was 17.   It actually ran when I got done,
AND I didn't even have any "extra" parts left over. P.S. The best screwdrivers are mac, snap on, cornwell, S&K etc. Others like craftsman are ok I think. Problem is the cheepies don't have hardened tips and will deform both themselves and the screws.
Please note MHO..

[legendary]

Andy750,
               check these out:



The offending screws



Handled....valve cover off. No noticeable gasket adhesion issue ...with all the screws removed. :-)
This is why I always ask before applying force.



This is my valve train...looks nice and clean. Cam chain isn't sloppy. Pleased with this... looks good so far.

That was probably 15 minutes from asked- answered, valve cover off. Took longer to load up the pics.

[legendary]

"Once you get the valve cover off, things will get interesting."

jsaab,
         this has me thinking.... have you ever seen a plastic tray made specifically for keeping v8 engine internals organized during a rebuild.  Might be nice to have on of those for a CB750......hmmmmm.

Appreciate the advice on keeping the parts organized and on the screwdrivers. As you'll see from my last post I am at the valve train. I am working 12 hr shifts the next 4 days so next progress will be Sunday.

New Question for Sunday: Any advice on removing the cam chain master-link or is it pretty self-explanatory??

[scunny]

the chain wont have a link. just undo the 2 cam sprocket bolts then you can pull the cam away from the sprocket. make sure to tie something to the cam chain cause you don't want to drop it down the tunnel

[jreich]

Someone quite awhile back had mentioned a good method for keeping bolts/nuts organized as to where they should go upon rebuild. Draw out on cardboard each section that you are working on. Then poke the bolts through the cardboard in their respective positions. If then needed, screw the nut on the other side.

I know that on my first bike tear down, I labeled zip-lock bags for my bolts/nuts, and even then didn't get everything in the right hole the first time around.

[dustyc]

When I take something apart, I grid a piece of cardboard with 1" squares, then poke holes at all the line intersections and write front on one edge.  Then as I disassemble whatever it is, I put the screws in the cardboard in a way that makes sense.  If it has washers or nuts, I put them on the front or back as called for.  It makes putting things back together exactly the way they came apart very easy. 

I do it because some screws end up with a burr that will only match the hole it came from and will be a pain to put in a different hole or worse, damage it.  Just my observation and how I do it.  I have hundreds of cardboard grids of various sizes with holes that I tend to reuse.  Typical size is under a foot square, so they can fit in a gallon ziplock.

jreich posted as I was typing.  I'm glad to see someone else has a similar madness.

[jreich]

Dusty,

You're probably who I originally got the idea from!

Cheers
JD

[754]

Measuring cylinders..

IMO, it pretty tough to measure these yourself. Even when I was selling pistons but not boring, I usually sent customers to the engine shop to get them checked with a bore guage.. and guess where it will go if it needs boring?

The problem is accurate measurement is time consuming with a telescoping guage and mike, and a bit much for trhem not used to it. Checking for taper & out of round.

I am not much for honing it when it is wore over limit and spending the price of a gasket set and rings, plus all the labour to do 1/2 a job that wont last a long time.. Or lapping valves when they really neeed cutting and valves ground..keep in mind there is a bit of power to bew picked up in a good muti-angle valve job..


Just my thoughts.. for all the time and cash involved, lets do it right..

[jsaab2748]

+1 on dustyc's last post. I've done/still do use that method when donig automotive engine work. I rebuilt a 302 Ford engine(reassemb.
led) six months AFTER I took it apart. But I digress...I'll quit rambling and let others post now

[paulages]

i have a few rebuilds in progress: a cb750 stock, cb550 stock, a cb550/650/750 718cc combo, and a cb350T. i'll take as many pics as possible and contribute if it won't be cluttering the original topic makers' progress. if so, i'll start a separate thread if it will help people.

[smack doogle]

Okay, sorry for the delay in getting pictures to you all.  After I got the engine out I took the valve cover off.  Like it was said above, be sure to remove the breather cover and loosen the two screws under that.  That's all of them.  Mine were on tight but not to bad.  No heads were stripped but I don't plan on using these again anyways.  I'll be going to ebay for the nice stainless hex head bolts.  After I got the cover off I read and re-read numerous times (in the manual provided here of course) how to remove the rockers and cam shaft.  One discrepency in the manual is the number of bolts it says are holding the rockers to the big pin.  The manual says one but I found there were three for each rocker.  Good thing I took out the bolts before I started driving out the rocker pin.  I was very careful just to tap the pin out and once I got it to move a little it slid out on the oil that was still in there.  Very simple but once again I took my time and did it nice and slow.  Once I got the rockers off I went to work on the camshaft. 
You quickly realize the camshaft isn't going to come right off even with the cam chain adjuster off so I read the manual and searched here.  I found you must remove the sprocket and the chain will come off.  Low and behold the chain came right off as soon as the sprocket was off.  The camshaft slide right out and it shows no wear on the lobes at all.  I put the sprocket back on the camshaft and put that away for safe keeping along with the rockers which I reassembled and put in labeled zip lock bags for safe keeping, all hardware included in each bag.

[smack doogle]

Next up was the head.  I was very curious as to what the pistons looked like so I read and re-read the manual once again and it seemed pretty easy.  Just be careful to loosen according to the manual.  I didn't need pry and beat it up to get it to move once all the nuts were off the studs.  I just bear hugged the engine, lifted the whole thing off the stand and wiggled and shimmyed and slowly but surely it slid off the studs.  I don't plan on replacing the studs.  It sounds like a lot of work and big chances made if not done correctly.  The head off the cylinders look pretty dirty.  Not to bad I guess but I haven't seen enough in my life to really tell good from bad.  All I know is that there aren't any holes in them so that's a plus.  Them I took a peak at the valves.  WOW, those look horrible!!!
So, I read and re-read the manual on valve removal.  That doesn't look easy, it seems they use a big C-clamp in the manual to compress the spring.  I might need to study hard and take a minute before I tackle the valves.  Next step, either split the case (seems pretty simple, just lots of bolts to loosen) or the valves.  Don't know yet.  This was enough for one day.
Heres the pistons
 

[smack doogle]

Heres the valves

#1
#2
#3
#4
Not to pretty

[smack doogle]

I think I'm gonna take a break on engine work the next few days and switch it over to sanding down the frame and swingarm.  My head hurts and sanding isn't to mentally taxing.  If anyone in Mass. needs some sandblasting done Hanscom AFB skill center has a sand blaster, DIY for $5/hour.  Just throwing it out there, oh, I can get you on base if that's a problem. 

How you coming Legendary?

[markb]

I picked up a valve spring compressor at Sears for about $20 that works just fine.  They've got a couple for about $80 that didn't look like they would work any better if you decide you want to pull the valves out yourself.

[Honda?]

Why didn't you seperate the head from the cylinders? The HG comes with the Cycle X gasket kit anyways.

Oh and I'm lovin this thread! I'm rebuilding my engine too but I won't be splitting the case.

My progress to this point...

[Terry in Australia]

Ha ha, I guess SD hasn't noticed that the cam towers have to come off to remove the 6 rubber "pucks" that hide the four 6mm bolts that secure the head to the cylinder block! No biggie mate, and don't start pulling out valves until you get back to us, you may not need to! Cheers, Terry.

[smack doogle]

   You mean there's screws under those rubber thingies?  I'm gonna go check that out.  That would make sense and valve removal and stuff a WHOLE LOT EASIER.  See, that's why me and Legendary came here and decided to put our rebuild together.  Already I feel warm inside with knowledge.  The warmth might be from the few bloody marries I've had this afternoon 

Thanks guys.  I'll post once I investigate this and have some more pictures.

[Honda?]

Haha this is my first rebuild too but I had to find those pucks because one of em was the cause of the oil leak I was looking for.

Just cross your fingers and hope you dont find anything like this anywhere!...

[Terry in Australia]

Ooo-er that's scary, and brings back memories best forgotten..........................

[Honda?]

So since this is an engine rebuild thread lets get a noob question of mine out of the way.

Why do you have to hone a cylinder and replace piston rings? What happens if you dont?

Good source to buy rings? and maybe a DIY honing page? (I'm sorta at this point in my engine rebuild.)
And while I'm here.

[Terry in Australia]

Here you go mate:

http://cgi.ebay.com/ebaymotors/FOUR-New-Honda-Piston-Ring-Sets-CB750-CB-750-Std-Rings_W0QQitemZ170182540057QQihZ007QQcategoryZ35594QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I bought a set, and they look fine. Your pistons though, are looking close to "bin quality". Before you buy any rings, you need to measure the "piston to bore" gap with a set of feeler guages, if you've got more than about .004 gap, don't spend any money on rings, take it to a shop and get them to measure the cylinder bore to see what's worn out. (pistons wear on the "thrust faces", and cylinders "oval" with wear) If it is, you'll need to get them bored to 1st over size and buy new pistons and rings. Cheers, Terry.