1981 CB750K - Ruby - 90K km's

[seestheday]

Minor updates again.

Managed to get all of the valves lapped.  Next step is to test to make sure they're solvent tight.  Gonna put all of the springs etc. back in, tip the head on it's side and pour paint thinner into the intake ports.  I'll look for seepage on the valves to see which ones I need to redo.  After I do the intake ports I'll flip it over and repeat with the exhaust ports.

I am also very happy to say that I don't have to pull the cylinder block.  I was afraid I was going to because the brass wheel I was using to clean the tops of the heads decided to fall apart and I got a fair amount of wire bristles stuck beside the cylinder (it wasn't fully at TDC like it should have been ).  Anyways, I managed to fish them all out with a q-tip, and slightly moving the piston up and down.

After that, I'm re-assembling it all.  Can't wait to put the 900 cams on (for real this time, not the 1100F's).

I also put the 900F rear shocks on with the piggyback oil reservoirs.  I'll post a pic of those shortly.  They were just a bit longer than the stock 750K shocks, so I'm hoping it won't make much difference.  The rear wheel on the centre stand still clears the ground.

[shinyribs]

Hijack: Did the 900F's come with piggybacks stock? I've been wanting piggybacks for a while but the price for a pair of new ones is more than I can justify. If I could score some old stockers of Ebay that would be great. Just wondering what to search for.

[seestheday]

Yep. No idea how good they are, but I only paid $25 for the pair. Figure they can't be worse than the stock K shocks I was running. I think it is later 900f models. Not sure when they started, but it may have been 1981 or 82. Bike ended production in 1983.

[shinyribs]

One more shock question hijack and ill quit. What is the length of those shocks? The back end of my bike needs to come up. Also wondering if the eyelets are that same as sohc bikes. Thanks.

[seestheday]

Sorry, I meant to measure them last night but it was too damn cold (-14 degrees C).

Here is the info from the FSM, but I don't think this gives you what you need:

[Johnnylevi]

if they're the same as the 750 DOHC they're 14.25"... eye to clevis

[seestheday]

They were about a 1/4 inch longer than my stock K shocks.

[shinyribs]

Awesome.Mine are 13 1/4,so another 1- 1 1/4 is exactly what I'm looking for.Thanks guys. Of course,$100 is the cheapest I've been able to find a pair. Stupid cafe craze....it has all the prices inflated.

[seestheday]

Woohooo! My valve stem seals finally came in.  Jebbysan was great to deal with.  Don't take my experience as standard.  Looks like the post office lost the first set, so Jebbysan sent a 2nd set as soon as I contacted him (I had already waited 5 weeks).

I got all of the valves mounted with the springs two nights ago, so now I'll test for leaks with solvent and start putting it back together

[seestheday]

Damn, its been a while since I last updated this thread.

During the re-install I've been using anti-seize,, thread locker, and assembly lube where appropriate.

The moly assembly lube was $20 for the bottle, but apparently it'll likely last me for the rest of my life if I store it right.

Valve all back in and properly seated.  I tested them with solvent and only a few were leaking.  Pulled the valves again re-lapped them.  Got them all sealing solvent tight.  More carbon build-up came out of the exhaust port while I was doing this.  Damn those things were gunked up.

Lots of care taken to ensure that the upgrade valve stem seals mounted properly and the springs were properly oriented.  The directions in the FSM were great for this.

Cylinder head mounted.  I only pulled the head, not the cylinder.  I tried to a bit but it was _very_ stuck so I decided to just leave it.  I'm hoping that this doesn't come back and bite me in my ass.  There is a great instructional on the cb750c site by Frank on how to mount the head if you want pics  (http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=12228)

I mounted the head, put anti-seize on the threads and torqued it down, and then realized that I had neglected to install the cam chain follower.  Dammit.  Head came back off, cam chain follower installed, head back on and torqued down.  I'm hoping that this mistake doesn't cost me significantly as well.  It is my understanding that you can't re-use the head gasket, but I'm guessing that since it didn't run I should be fine.

Valve shims back in appropriate spots.

Cams and cam chains installed.  Assembly lube on every contact surface for the cams.  Assembly lube in the cam tower dowels to ensure that they slide out easily when I have to pull this engine apart again.

Red loctite on the cam chain sprocket so it doesn't come loose on me.  Anti-seize on all cam cap bolts.

Again, a great thread by Frank on the cb750c site if you're looking for an instructional and pics. (http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=12100)

One thing that isn't clear from the Frank instructional is where to put the metal/rubber oil pool caps on the exhaust cams.  They go on the side of the cam caps that face the exhaust port on the two innermost cam caps.

I also installed 900 cams instead of the 750 cams so I'm hoping for a nice bump in mid-range power.  Since my cam chain was worn the alignment dots aren't lining up perfectly.  I'll get a new cam chain and cam chain tensioner when I pull the engine next time (probably next winter).  That is when I will pull the cylinder and probably do a lot of cosmetic work.

After getting the camshafts properly set up I fixed my valve cover bolts with new seals and installed them.  Pic of old vs. new.



Replaced all of the easily accessible side gaskets.  Put anti-seize on every outside bolt and torqued them to spec.

lifted the engine off of my wooden stand and pulled the oil pan gasket.  This doesn't look precarious does it?


Ha ha, just kidding.  Laid it on it's side with no issues to get the oil pan off, I just thought it was funny that it balanced there quite well.

Inside the oil pan was better than I expected.  The last time I opened it up there were some fairly sizeable aluminum chunks & shavings, along with a fair amount of gasket material.  This time there was just a few tiny specks of aluminum.  I suspect that this is just the leftover remains of my cam cap tower that broke and it's cycling through.

I pulled the strainer and considered putting a new seal on, but the one I had was still _very_ snug, so I decided to leave it.  I believe I read a thread here about someone having a loose fitting issue so I didn't want to take my chances and my seal looked great.

Cleaned up the pan and put it all back together.

I started to clean up the bottom of the engine but it was after midnight so that will have to wait until tonight.  My brother is coming over Sunday to help me lift it back into the frame, so it's all got to be done by then.

Next up:
- Clean the bottom of the engine
- replace oil filter
- put engine back in frame
- put new oil in
- hook up wires and make sure everything works
- figure out if I'm going to wrap my headers or blast/paint them
- install headers/exhaust
- install freshly cleaned carbs
- start it up & sync the carbs

I'm dying to get out and ride, so I'm going to wait to paint the tank & side covers, but that will likely be my first cosmetic job on this bike and should happen before summer.

[seestheday]

Oh, and here is a pic of the 900F shocks I mounted.

[Butcherblock]

Great to see this thread back up at the top Sees. I have been watching it since I came to this site. Sounds like it is all coming together now,I can't wait to here how well it runs. Goodluck on the reinstall, hope it all goes together well!

[shinyribs]

You've been busy! Good job bud. Glad to hear it going your way. Man,I really need to pick up a pair of those shocks.

[seestheday]

This is what everyone drinks when they work on engines amiright.....?



Damn gluten allergy means I'm drinking wine or hard liquor these days.  Don't get me started on gluten free beer...

Bottom of engine cleaned and oil filter changed last night.  Engine degreaser wasn't really doing the trick, so out came the oven cleaner.  I was really careful not to get it on any gaskets or seals of any kind though, and didn't leave it on for long.  Finished it off with a soapy water wash.

Used a cloth, brass brush, plastic brush and a rag wrapped around a screwdriver to get into all of the nooks and crannies.

Nice clean engine.  Can't wait until Sunday when it's getting put back into the frame.  I know it's not nice and painted or powdercoated like some of the beauties on this forum, but it is a big improvement over what it was.

[seestheday]

Engine mounted



Next up:
Give the frame another good clean while everything is easily accessible
Pull all Engine mount bolts and die/lube/anti-sieze the bolts to clean the threads and make sure they torque properly (didn't have time to do this with my brother helping me get it in)
Torque them all down to spec
Fix a broken nipple on the airbox with superglue (the one going to the reservoir box)
Fill it full of new oil (new filter already in)
Connect up the electronics & battery and make sure everything works (indicators, headlight, starter motor/clutch, spark, neutral light, oil pressure light...)
Put airbox in
Put carbs in
wrap headers (I just put some rust convertor on them to get rid of the surface rust they did have)
Start it up and make sure it is firing
Check for any vacuum leaks (new carb insulators and o-rings on carbs so I should be good)
put exhaust on  (want to make sure it fires before I waste a set of crush washers)
Sync carbs with my carbtune (already bench sync'd)
Use timing light to make sure it's timed right (never done this before, so I'll have to figure it out)

I'm sure I'm missing a few things in there, but that is my plan so far.

[seestheday]

I'm really pushing to get this done.  Picking it up in the home stretch.  Was up until 3am last night because I just couldn't go to bed without at least getting the headers wrapped and the exhaust mounted.

Progress made recently.

- Completed everything in my previous post except for syncing the carbs and checking the timing.
- I found that my blinker was performing poorly, so I drove down to Sirius and bought a new one (along with header wrap, race wire and some tubing)
- I ended up re-using my old header collars.  New ones from Honda would have cost me $80 and I didn't have time to hunt around bike salvage yards.

Damn those new carb insulators were TIGHT!

I also found out that after I got everything hooked up that my cables were routed incorrectly, so my carbs had to come back out and get re-installed .

Ditto for my clutch cable.  

I also have to comment on the first start.  Before I hooked up the headers I decided to see if it would fire.  Put the tank of seafoamed gas on, hooked up the fuel line with a filter, turned the key and hit the starter button.  The bike shocked me how fast and strong it started .  I was expecting a lot a rough starts until I got everything dialed in.  

It literally turned over twice to suck in gas, and then fired strong on the third turn.  

It goes without saying that with the headers off it was LOUD in my garage.  

Up next:
- Align rear wheel and tension chain
- Hook up rear brake
- Sync carbs
- Check/Adjust timing
- Dial in air/fuel mix
- Get idle to ~1,000 RPM
- Test ride
- Check front brake (I suspect it's spongy and needs to be bled)

Sooooo close....

[shinyribs]

It won't be long now! You've been getting alot of work done! Good job bud.

[seestheday]

Everything is back together and I'm riding her now.  Damn she pulls hard.  It feels like the front wheel wants to come up now when I do quick starts.

A few things to do before I'm "done".

- Drag bars are just barely hitting the tank , so I've ordered some superbike bars.  I want to keep my turn radius and I am not up for hammering in dents rights now.

- Indicators are sticking on even though I just purchased a new thermal replacement flasher.  I'm just going to go with a digital one and be done with it.  That way if I decide to get other LED indicators in the future that part is also already done.

Got my idle down to 1,000 - but it almost wants to stall.  Think I'm going to turn it up to 1,100.

I am going to ride it for about 250 km's and then re-tighten everything needed after the break-in period and re-check the valve shims, check the sync on the carbs etc.

Now to plan the painting of the tank and side covers....

[seestheday]

Update - break in period complete.  Re-tightened all head bolts, checked valve lash and found one that was at .002" and one that was at .007".  I switched a few around but still ended up with one left at 0.003".  I bought a new shim and will be installing it sometime this week.

Changed the oil and filter and it was a goopy mess .  It was like sludge.  I was surprised as it had only run in the bike for 180 km's, but I've since read that this is typical of a break-in oil change.

I also managed to drip oil all over my nicely wrapped headers when I pulled the oil filter.  I had put a rag in there, but there was still a lot of thick sludgy oil that soaked through.  I'll be putting something a little more substantial there to catch the oil next time.  After a few smokey runs the oil burned off the header wrap .

Blinker update.  After spending a few hours testing every wire from the light to the controls to the battery I found that the damn light on one side had come loose inside of the housing.  .  I also now have an electronic flasher so if I want to swap out full LED's I can do that now.

Dammit, always check the fuses and make sure that the light itself works.  Oh well, I know a lot about the loom now.

[free2ride]

I am just in awe at everyone here who does his [her] own work.

Looking forward to seeing this bike!