MY 1979 CB750 DOHC BUILD

[Hoosier Daddy]

RodneyCB750K1979 wrote

I need a way of putting the engine back in.  My son said there is a posting that describes a hoist method that uses the motorcycle stand like I have from harbor freight and a piece of 2 inch pipe.  I'll definately not install the exhaust studs until the motor is back in.

Am I missing something here? Put it on a floor jack and roll it in from the right side then raise it into position... That is why that side of the frame section is removable.
 Granted I haven't put mine back in yet but I can not imagine it would be much diiferent than my 81 GL's

[750K8]

You may want to use this time to think about getting the frame blasted and powder coated, depending on the condition. There will be no other time to do it than now.

You will definitely want to go ahead and replace your sprockets and the chain. I used the stock gearing for my '78k, even though it was previously modified for the 520 (or 530, whichever it is).

Your tires looked good from when I saw it, so I wouldn't worry about them yet.

Take a look at your brake pads/shoes. The manual gives the proper clearance. Very cheap and easy maintenance.

Lube your choke/brake/throttle cables with some white lithium grease. It works wonders on these old bikes, and made me control my friction zone much better on my '78k.

I'm 6"4, so the '79 seats are horrible for me because they force my balls into the tank and my legs are really squished. Not sure if you have the same problem, so now is the time to confirm if the bike's seat doesn't need any modification. My stock '78 seat was a big improvement, though I didn't like the additional padding and I still would prefer to not be slightly forced into a seating position, so I went with the '77 seat and have been in heaven ever since.

How are the wheels? Now is the time to get those powder coated if necessary. Don't use rustoleum on stuff. It's just messy and more work for you in the future.

Now is a good time to undercoat the fenders. Honda to my knowledge, puts nothing on the other sides. They are bound to rust. Some good cleaning, zero rust paint, and some undercoating leaves for a nice durable fix.

Are the shocks leaking? The stock shocks were never really meant for 220lbers. They remind me of pogo stocks. I got some Hagan shocks on mine, and it really stiffened up the ride and made the suspension more agile which gave for a firmer, more responsive ride.


Does the gas tank need to be purged? Is there rust inside?

[RodneyCB750K1979]

Thanks for the suggestion. I will definately try the floor jack approach. I really knicked the heck out of the frame when I horsed the engine out.  

[RodneyCB750K1979]

I don't know about stripping down the frame. Looks easy at first. But we're talking removal of the wiring harness, front forks, fenders, swing arm, stands.  I really intended on just getting the engine running good so I can drive it a bit. The frame appears clean with little corrosion going on. It still has a gloss black appearance.

[RodneyCB750K1979]

I finally completed my carb rebuild this evening. And I was only missing two screws.  I ordered new stainless steel button head phillip screws for the carb bowls and front/rear rails. I installed stainless steel socket button head screws in the choke plates and assembled using Blue Threadlocker.

[RodneyCB750K1979]

I removed all the exhaust studs.  One was stubborn but finally came out with heat, candle wax, and rapping with a hammer. I ran a tap to clean up the threads.  I'll install new studs using a copper-based anti-seize compound.

[wingman1946]

FYI: The original item was NOT Phillips. They are Japanese and require a Japanese driver.

[Hoosier Daddy]

J.I.S. (Japanese Industrial Standards) similar but easily rounded with standard Phillips screwdrivers.
http://cycleorings.com/phillips.html

Usually identified by a "dot" between the cross....

[RodneyCB750K1979]

I checked the piston ring end gaps. Most were within tolerance. A few were outside but could be measurement error.  I want to install them. Any thoughts?

                              Cylinder 4   Cylinder 3   Cylinder 2   Cylinder 1    Allowable
Top Comp Ring         0.012          0.013       0.014      0.010           .004-.012
Second Comp Ring    0.012          0.013       0.012      0.012           .004-.012
Top Oil Ring              0.022          0.022       0.022      0.017           .012-.035
Lower Oil Ring          0.021          0.021       0.021      0.018           .012-.035

[TOOLS1]

Better too big of a gap then too little. Go on and install them.
TOOLS

[shinyribs]

^^^^Agreed. Once again,I ditto Tools.

[fire101]

Hey how much did it cost you to get your valves Worked on? I was going to do it my self but dont have all the tools that i need. I am also working on a 1979 CB 750k Limited edition.
I ended up boring it out and put 63mm oversized kit in.    

[seestheday]

What tools are you missing? You can make you own valve puller for under $20 (or a lot less if you already have a large c clamp).                                                                                                                                      

[RodneyCB750K1979]

I think I got ripped off.  I paid $490 and I they supplied and installed 2 new exhaust valves and a set of valve seals, lapped the valves, and lightly honed the cylinders. I also requested the jugs and head to be dipped and cleaned and a broken exhaust stud be removed but these weren't done.  I hope I don't damage the valve seals when I now go to clean the heads using engine cleaner and lacquer thinner.  My reference is I paid about half of this to have new valve springs and seals put on my Mustang's cylinder heads.

[RodneyCB750K1979]

Is there a special tool needed to add/remove lifter shims?

[Hoosier Daddy]

yep, looks like this...


Now you won't add or remove shims, you'll change THE shim on each valve.

[seestheday]

I believe that Fitz from the cb750c site will rebuild your head for ~$200.  You just have to ship it to him.

His contact info in the link below.  Given that those guys specialize in the DOHC CB's, I'd trust them to do it right more than a random local shop.

You may need to register to see this link.
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=21629

[RodneyCB750K1979]

Thanks for the lead.  I wished I'd known this a month ago.

[RodneyCB750K1979]

I'm looking for some advice on replacing the chain and sprockets. My 1979 Honda currently has a 330-15 drive sprocket and a 41T rear sprocket.  Not sure what the OEM sprocket sizes were. What is the best style of chain (o-rings and non o-rings).  Any help is appreciated.

[RodneyCB750K1979]

Update February 5.  Took the day off from work to do some work on the bike project.  I tackled the dreaded job of cleaning the engine components. I used some brushes and lacquer thinner. Someone in the past used what appears to be hardening gasket sealer on the oil pan gasket. It took some work using a razor and wire wheel to remove it all.  I removed the oil pump pickup screen to clean it and noticed it wouldn't go back on tightly. The rubber grommet must have shrunk.  Need to get a new grommet before I can install the oil pan. Discovered the neutral safety switch wire had damaged insulation and the wire was exposed. Will need to repair the wire. Cleaning between the cooling fins on the head and jugs was a very difficult task.  Ended up using my paint gun cleaning brushes to access all the small spaces. I spray painted the oil pan and jugs with Rustoleum Hi Temp Paint. The oil pan actually looked nicer without the paint and I may strip it later on.  Does anyone have any concerns painting the cooling fins with this paint? Any issues with reduced heat transfer, peeling, or discoloration?