1981 CB750K - Ruby - 90K km's

[seestheday]

Made some great progress today.  I was worried about the head being really stuck, but when it came time to pull it off, I just pulled on it and it easily slid off.  Kind of surprising given how stuck those camshaft covers were.

Things I have to figure out now:
- My intake cam is just slightly past tolerance.  Do I definitely need a new intake cam? - UPDATE: yes - might as well get 900 cams
- Figure out if the valve spring compressor tool listed for SOHC's will also work for the DOHC - UPDATE: kind of, there is a good thread on the cb900 site for some similar valve spring compressors that I'm going to use.  I got a free rental of a valve spring compressor from an auto parts store and it definitely doesn't work (didn't even try, it was obvious)
- Figure out how to pull out the stuck cylinder head dowels out
     - these are the ones that I had trouble with and there is noticeable corrosion on them.  I don't want to re-use them and they are really stuck.  They're currently soaking in liquid wrench - UPDATE: had to use easy outs to pull most of them.  One is still super stuck.  I have been able to get some movement on it though, so that is promising.  Currently soaking in liquid wrench. - 2nd UPDATE: Got that damn thing out.  Pretty sure it was all scored up and the damn PO hammered it back in instead of buying a new one.  Really hoping that that the camshaft holders aren't out of spec because of this.

Things to buy
- Order at least 1 replacement cylinder head dowel.  One for the gear/tach tower was visibly deformed.
- Order a new cam chain tensioner (see pic)

Disaster averted?  The crack in the cam chain tensioner goes almost all the way through.


More pics

Keeping track of the shims


Immediately after I pulled the head off.  Lots of carbon on the tops of those pistons.


The side where I saw air bubbles when it was running so I knew the head gasket was blown


What it looked like with the old gasket taken off.  Lots of crap on both sides of this gasket.  


Cleaned head.  Still need to polish (scratches that you see here are very small and will come out with polishing, they're from the gasket scraper.  Still, I'm not happy about those scratches ).  Also still need to clean combustion area.

[Piute]

    Hey,
  See's next time your at a place that sells counter tops or Masonite ,
  grab a few samples make great scrapers and wont gouge metal,
    Got my stack at Lowe's (of course)

                                                      "O" and there FREEEEEeee

[seestheday]

Ya, I used a plastic scraper that I thought wouldn't scratch the metal. It said it was safe in the package, and I figured since it was plastic there was no way it could scratch aluminum. I was wrong :-(.

[seestheday]

Here's the list of stuff I figure I need so far:
(I already have a gasket set)

- New vitron valve seals (strong recommendations from the cb750c to not use the ones that come in the gasket set) ~$30 (Jebby @ various dohc forums)
- oil diverter caps ~$18 (Honda)
- cam chain tensioner ~$100 (Honda)
- camshast cover dowels (I'll likely need at least 5) ~$3 each (Honda)
- a way to lap the valves.  Given how much carbon buildup I have, I'm pretty sure this inevitable.  135 compression is apparently not very good for a dohc.  I should really be at 150-170.
- Timesert/heli-coil for cam chain tensioner adjuster (I felt the threads start to go the last time I adjusted the tensioner)
- tach drive seal (its leaking oil)
- cam chain tensioner seal (leaking more oil)

I'm also running into the "how deep do I go" question.  Now that the head is off, why not clean the carbon off the valves and relap/reseal them?  I should really clean all of that carbon off the pistons, so that means pulling the cylinder... Well, its close to the end of January now, and I really want to get riding when I can first get on the road, probably around March.

[shinyribs]

Just a heads up for future reference,lighter fluid dissolves most any gasket really well. Not the lighter fluid you use to start a grill,the kind you use in a Zippo. The fumes are not bad at all since it is designed to be carried in your pocket. Just squirt it on and wait a bit. Maybe 30 seconds,then scrape a little off. The stuff evaporates kinda fast so you will have to do several applications. But it works well. It'll help break down that carbon on your pistons,too. Also good for removing tar and bug guts from paint. Won't hurt your paint at all. It's a great degreaser,but obviously not for large jobs. Zippo brand fluid tends to be a bit more fumey than most. Ronsonol brand fluid has the least amount of smell,though the Zippo stuff does evaporate slower it seems.

[shinyribs]

These work well to remove old,baked on gaskets,too. Use the finer ones,not the coarse. Small scratches on that surface won't matter. The gasket will seal just fine. In order to create a leak a scratch would have to be so deep that you could easily hang a fingernail in it.

[seestheday]

Thanks Shiney, there is only one scratch where I can feel any resistance with a fingernail, and it's in a spot where it shouldn't matter if I have a seal or not. I'm just a little mad at myself for scratching it at all

[shinyribs]

Ahhh,don't feel bad about that. It's nearly impossible to do without scratching. It's not nearly as a big a deal as it seems. You'll be fine.

[seestheday]

Stuff coming up next:
- Inspect the oil pump (should have done this earlier)
- get a spring scale so I can measure the cam chain stretch
- figure out if I can check the camshaft runout without buying a dial indicator & stand
- check camshaft holder limits with plastigauge
- make a valve spring compressor
- remove the valves
- check everything to do with the valves to make sure they're still in spec
- de-carbon/clean the valves & combustion chamber
- get lapping tools & compound
- re-install the valves with new vitron valve seals
- inspect the A chain cam tensioner
- finish putting on the controls (got a new flat drag bar on instead of stockers)
- fix the routing of the front brake and other cables (may need some shorter cables)

lots more after that, but that's the current plan

[teamvivivi]

great thread! im doing the same thing, im all the way down to exactly where you are. My cam chain tensioner was actually in worse shape almost all the way cracked in half, in 3 different places! Im in the same boat as to.. how far should i go... i too want to be riding soon! im about to start another project building a cb350 for my wife. Iv had it for at least 10 years now... just sitting under a tarp in my back yard.. im kinda nervous to even see what kind of project im getting myself into! anyway keep up the progress its definitely keeping me moving on mine! so thanks!

[seestheday]

Thanks Teamvivi, I appreciate that I'm inspiring someone .  Keeps me motivated as well.  

Last few nights have been too cold even for me.  -20 degrees Celcius, but it'll warm up to almost freezing (0 degree Celsius) soon so I'll get back out there.

[seestheday]

List of stuff I need to buy.  I'll update this post as I get stuff or need more so it's all in one place.

I'm trying to compile the complete list to see if it will be significantly cheaper to ship it from the US, or just get it locally at the dealer.  Dealership seems to be about 40-50% more expensive, and shipping costs flatten out once the parts list is long enough.

Edited for my clarity.

Already bought
Drag bars - $36
Bar end mirrors - $24
cb900f piggyback shocks - $25
Oil poll caps - bought ($15.80 before taxes from Honda dealer, would have been $10.20 from partzilla)
Viton Valve Seals - $24 shipped from cb750c.com member
cb900 cams  - $60
valve cover bolt seals - $20 (vintagecb750.com)
C clamp and 1/2 inch PVC pipe to make valve spring compressor (works great!)
Helicoil kit for cam chain B tensioner adjustment hole (~$18 I think, can't remember)

Need to buy:
camshaft holder dowels (probably 6, I'll double check $3.38 each on partzilla)
cam chain B tensioner (list for $91 on partzilla)
Tach Oil Seal ($2.87 partzilla)
Cam chain B tensioner seal ($3.37 Partzilla)
Valve Shims - unknown quantity (will know once I put things back)

[shinyribs]

seestheday wrote

 but it'll warm up to almost freezing (0 degree Celsius) soon so I'll get back out there.

   Stay warm dude

[Hoosier Daddy]

seestheday wrote

valve cover bolts (full set - $75.60  - maybe I should just re-use what I have)

 Do you need the Bolts or just the sealing washers???

I got these from Vintagecb750.com for $20 plus he's a Canook.

[seestheday]

All I see on that link are sohc parts...                                                                                                                                      

[Johnnylevi]

There's a drop down bar on the top left of the screen you can select your year/model there and only parts for your bike will appear. :D

[Hoosier Daddy]

Johnnylevi wrote

There's a drop down bar on the top left of the screen you can select your year/model there and only parts for your bike will appear. :D

^Yeah, that right there.^
Did you click on my link? I thought it would take you right to the engine page they are on for your 81 K model.

[seestheday]

Don't know how I missed that.  Must have been because I was looking on my phone.

Oh well.  I went through and planned to order a whole bunch of stuff from that site because it is significantly cheaper than from the dealership, but they're out of stock on both those cam cover seals and the B cam chain for my year.  Email has been sent to the site owner to see if they know when they'll get restocked.

[seestheday]

Ok, updates

Ordered a whole bunch of stuff, hopefully it doesn't take too long to ship.  I will have to go back and update that post where I'm keeping a tally of everything I am buying.

I was able to get the cam cover seals when ordered separately, but if I bought them as a pack they were out of stock.  I thought it was strange because the price was the same either way.

Looks like I have to order a B cam chain and B cam chain tensioner from Honda as they are sold out elsewhere.

I've been spending some time cleaning the combustion chamber.  The carbon on it was super thick and baked on.  

Here is a pic after I've spent several days going through rounds of soaking it in varsol, followed by a wire brush in the dremel.  It's currently soaking in seafoam deep creep which is supposed to loosen carbon & rust specifically.  Not sure, but I might have gouged one of the exhaust valve faces a little bit when I was trying to knock down some really think carbon with an *ahem* inappropriate Dremel bit.  .  If I have to order a single new exhaust valve I guess it isn't the end of the world though.



New drag bars are on and controls mounted.  Electrical wires re-routed easily, but I have an s-bend in my brake line that is concerning to me.  Might replace with a shorter stainless steel line.



Managed to crack the plastic on the left hand control while I was tightening it down.  I have a spare cb900 left hand control that I might swap in, or pick up a nicer looking one.  Anyone have any suggestions?  It'll need to be reasonably priced...

[seestheday]

Searching around and maybe something like this would work?

http://www.cheapcycleparts.com/products/55287-biker-s-choice-70505h4-switch-custom-handlebar-switch

The part listed is for an "XL big twin" handlebar, so I guess that means ATV , but I'm hoping for something simliar that will work with the Honda wiring.