1981 CB750K - Ruby - 90K km's

[Piute]

       Ruby That works ,But your stuck on a color Ya thiunk

   I had winter Blizzards on my Elc that took thoughs rivit studs never had to use,(studs)
        but carryed them ,Heck with the
        I'm just getting home safe (would be my story)

[Beekeeper]

I believe that is part of your crankcase breather system.   If you have sludge and liquid backed up clear to the Y connector, better pull the plug on the reservior under the battery box and drain it.  If I understand that part of the system correctly, I would look in the breather box too, since that line vents through the airbox before emptying into the reservior.  

[seestheday]

Ha, yes I was already planning on having red somewhere.  Possibly the frame.

I do want to keep my high vis helmet, so I also want to figure out how to incorporate something so it doesn't look terribly our of place.

[seestheday]

Dammit, I knew that box existed but I thought it was only on US bikes.  I just checked my bike and yep, the Canadian ones have them too.

I am pretty sure there are thousands of km's of sludge waiting in there for me.  I'll clear that out soon...

[seestheday]

pulled the air box and that resevoir tonight, it was dry.  i'll have to look elsewhere for the source of that liquid.

I did notice that there was no plug on the bottom of it and that it was just venting to atmosphere and in the manual it says it should have a plug.  I wonder if that is my issue.  I do ride in the rain a fair amount, not sure if it is possible for moisture to be making its way in that way.  I'm assuming that it should be pressurized in some way to prevent this.

[seestheday]

Oh boy, pretty sure I found the source of my vacuum leak issues



Here's how the bike looks now, carbs off, air box removed



Not sure if I did this while removing the airbox or carbs or if it has been this way for a while, either way, time to replace it.

[Beekeeper]

Following your thread closely.  I just got my VC gasket and seals.  Supposed to warm up a bit the next couple days so maybe I'll get started too.

[seestheday]

check out the wot compression thread too.

glad to heat you're getting value out of this :-)

http://honda-cb750-s.456789.n3.nabble.com/importance-of-WOT-during-compression-test-td4033339.html

[seestheday]

Well, I made a fair amount of progress last night.  I figured I'd get as much off the bike as possible while waiting for my leakdown tester to arrive in the mail (thanks Shiny ).  

I cleaned out the airbox and found some more sludge and stuff that was broken.

Exhaust, pegs, gear changer, brake pedal, final drive chain & sprocket have been removed.

I also put in the new starter clutch springs I bought from Honda.

Y air box connector full of that oil/water yellow/white sludge.  I might end up getting new air hoses and putting red filters on them directly instead of running through the airbox.  I have seen a few DOHC builds with this setup and I really like how they look.


After inspecting the airbox I noticed that the hose connecting the airbox to the reservoir that goes under the battery box was barely hanging on.  I removed the hose and the nipple snapped off very easily.  I'll need to repair this if I want to keep this airbox and use the reservoir again.


Exhaust if off, I will either need to repaint this flat black or just wrap it.


Removing the final drive chain and sprocket.  I'll need to clean out that mess of sludge before I put it back together.


Given that this bike has 90K km's on it, I'm pretty happy about how that sprocket looks.


Pic of what I believe is a head gasket leak.  The same oil pattern is on the other side of the engine as well.  
This is after I've cleaned the outside up a bit, I just haven't gotten in there extensively with a toothbrush yet.


Started to remove the starter/timing cover and found this fun stripped bolt.


Have I mentioned that this is one of my favourite tools?  Impact driver got that bolt out with a few whacks of the hammer.


When I opened it up I found this fun mess of sludge.


Before I took the timing stuff off I scribed a mark on the pulsar plate and a supporting tang so I wouldn't have to retime the bike.  Cleaned it all up and installed the new springs.  It was a very easy and straightforward install.

[shinyribs]

Good grief,what the heck is that stuff?!?! I've seen oil and water mix,but that looks like pure mayonnaise!  I dont know if it relates to DOHC or not,but if oil seeps under the cam tower seal it will come out the sides of the engine and appear to be a head gasket leak. Just putting it out there. Good progress man,keep it up! You're gonna need lots of rags for this one!

[seestheday]

Lol, ya at first glance I thought it might be high gloss caulking that a PO put there for some bizarre reason, but it had the consistency of runny mayonnaise.

Good thing I have a big box of rags.

I'll check for that cam tower seal as well.  Assuming that the dohc has one.

[seestheday]

I had some more time today, so I decided to tackle the carbs.  This time around I wanted to split the bank and do it all properly.  I have the McGregor manual, so I'm following that closely.

Splitting the carbs for the first time


Pretty sure that the two carb sync washers aren't supposed to be one on top of another here.  I'm guessing one should be on top of the spring and one below it.  Can anyone confirm?  All of my carbs were like this.


3 of 4 air cutoff valves had pinholes or small tears in them.  These are either getting replaced or will be just bypassed.  I'm still looking into pros/cons of bypassing.  Saving myself $80 in parts would be nice.


Showing people (and myself for later) where the choke spring needs to go.


Really difficult to see in this pic, but this is where two washers were stacked.  One was a lock washer (it's the choke spring assembly).  I'm guessing that this isn't where these are supposed to go.  I'll probably look up some blow-ups of the carbs and hopefully all of the washers are on them so I can figure out where these should really go.


Had to stop after removing the jets on the 1st carb.  Found out that my slow jet is definitely pressed in, so I must have an early 1981 model (later 1981 models had removable slow jets).  I hope to finish disassembling the carbs and get to cleaning them this week.

I'll definitely need to pick up a few new screws.  Those 3mm choke plate screws are not going to go back in easily.

[80cb750k]

I have an '80 and realize I have a bit of work I need to do on it.  I have been following your posts to gain insight, looks like we have some similar issues, I however know very little about taking apart and repairing an engine.  Good Luck.  

BTW I am also in Ontario and may be taking it out of storage it has been so blinking mild here.  

[seestheday]

Before I started working on this bike I knew nothing about . I'm pretty mechanically minded and have a degree in physics so I feel pretty confident that I can figure anything out. That said, this forum is great. Any questions I've had, this place has been able to quickly answer.

Whereabouts in ontario? I'm in waterloo.

Sent from my BlackBerry device on the Rogers Wireless Network

---

From: "80cb750k [via Honda CB750'S]" <[hidden email]>

Date: Sun, 16 Dec 2012 19:35:44 -0800 (PST)

To: seestheday<[hidden email]>

Subject: Re: 1981 CB750K - Ruby - 90K km's

I have an '80 and realize I have a bit of work I need to do on it.  I have been following your posts to gain insight, looks like we have some similar issues, I however know very little about taking apart and repairing an engine.  Good Luck.  

BTW I am also in Ontario and may be taking it out of storage it has been so blinking mild here.  

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[Beekeeper]

There is actually a small "U" shaped fork in the linkages for each of the sync adustment screw/spring to slide into.  One of the washers goes on each side of the fork.  You have them seperated in a manner that makes it hard to see.  But if you hold 1&2  or 3&4 together, you will see it.  In one of the guides I have, it actually describes removing those sync screws and making a record of the number of turns so they will be close upon reassembly.

[Beekeeper]

I found a pic, kinda grainy, but it might help

[seestheday]

Thanks Beekeeper.

btw, I found this via another site: http://www.motorcycleproject.com/motorcycle/text/keihin_idle_circuits_white_paper.swf

Great read on how the carbs work.  Definitely going to be bypassing those air cutoff valves.

[Beekeeper]

I have Mikes' site bookmarked.  Spend some time there reading occassionally.  He is also involved in rebuilding V-12 WWII warbird engines for the Reno racers.  I think he worked on Rare Bear

[seestheday]

Carbs are almost fully disassembled now.  I need to run out and pick up a small screwdriver so I can get the primary main emulsion tube out.  The slow jet is pressed in, so it will be the one I will leave in there.  I have read that it is possible to get them out with a drill, but I am ok with cleaning it with a wire.



I had a cheap jewellers screwdriver I tried to use for the primary main emulsion tube, but it broke when I used it.  The freaking thing was just glued together.  I bought it for almost nothing, so I guess you get what you pay for.  For some reason that seems to be a lesson I just learn over and over again.

I'm going to go in and clean out the accelerator pump per lucky's instructions on the DOHC carb cleaning thread .  Planning on having these carbs sparkling clean and running as smooth as silk.

Reading up now on what I need to do to get the carbs super clean.  Not sure if just using a pine-sol bath will be enough (it wasn't last year - but I didn't split the bank that time).

Also, anyone know of a decent place to get o-rings and allen head screws in Ontario that won't kill me with shipping from the US?  Seems like something I should just be able to get from a local store, but no luck yet.

[free2ride]

have you checked on the powersportscanada web site to see if they have anything available?

btw, I've decided I'm going to seize the day myself . . . maybe tomorrow.