Topic: Bike stored for 29 years - tips welcomed on oil flush and prep before startup

[lockeed]

I bought a 1977 CB750K about two weeks ago. Couldn't be happier, bike is 100% original with only 12,500 miles. It's been in storage since 1988.

I started by removing the carbs, spent the last 2 days cleaning them, they were very dirty and gunked up.

Next step was to change the oil and filter, but I was wondering if I should flush the engine or if there's something better suited for a bike that's been stored for so long.

Anything specific I should pay attention to? Put a little lubricant on top on pistons before startup etc...?

[Desert-SOHC]

I'd pull the oil pan and clean the screen too.  If it was mine, I'd pull the plugs and fog the cylinders with Marvel spray before doing a slow by hand kick through, no plugs or carbs on it.  I'd do that a few times while listening in various places.  New plugs, oil and filters, good clean carbs, adjusted valves and whatever the ignition needs, add fuel and fire.  There pretty hardy bikes, it should fire pretty easy.

[toma]

I would pull the valve cover and oil up the cams and rockers too. And any thing else that goes around or up and down. Real good possibility that the valve guide seals are inelastic too. 

[BomberMann650]

Mine sat for 15 years and the valve stem seals don't leak. 

As for flushing the lowers.  Filling with off-road diesel (red dye diesel) and cranking it with the kick starter a couple times will do it fine.  Fill with 20-50 and be ready to do a few back to back oil changes.

Might as well replace the intake gasket/tappet o-rings and oil pump o rings too.

[b52bombardier1]

I did the oil spray in the cylinders thing as advised above and kick cycled it through a few times - no problems.  I also sprayed oil with the little red straw through the valve adjustment caps towards everything I could get to for some good start up top end lubricant - my bike had sat since the late 70's.  My fuel tank and carbs were in sad shape with lots of re-fossilized fuel - de-rusted and lined the fuel tank. And changed the oil and filter as suggested above.

  Then, with a good battery and the spark plugs removed, I hit the starter button for 3-4 seconds to see if the oil pressure light would go out. It did.   Finally at that point, I felt it was safe to attempt a restart.   I have had a smile (mostly) ever since listening to the sound of those Jardine header pipes.

  The only thing that removed the smile temporarily since then was finding out that the aftermarket carb brass was causing me fouled spark plugs - a 12,500 ohm original spark plug cap also did not help.  With some no kidding OEM Honda Keihin brass / float assemblies and NGK spark plug caps, that smile has fully returned.

Rick

[Stev-o]

add fuel...

Id check/clean/service the fuel tank before adding fuel to it.

[Gene]

Logging on here to see your progress lockeed. Take a good look at all of your boots as well - carbs to head, air to carbs. If those have leaks you'll have some issues firing up first time.
Also, just for comfort, check for spark on all plug leads. WTH, takes no time and you'll know right away of there's an issue w/the fire.

[Desert-SOHC]

I did the oil spray in the cylinders thing as advised above and kick cycled it through a few times - no problems.  I also sprayed oil with the little red straw through the valve adjustment caps towards everything I could get to for some good start up top end lubricant - my bike had sat since the late 70's.  My fuel tank and carbs were in sad shape with lots of re-fossilized fuel - de-rusted and lined the fuel tank. And changed the oil and filter as suggested above.

  Then, with a good battery and the spark plugs removed, I hit the starter button for 3-4 seconds to see if the oil pressure light would go out. It did.   Finally at that point, I felt it was safe to attempt a restart.   I have had a smile (mostly) ever since listening to the sound of those Jardine header pipes.

  The only thing that removed the smile temporarily since then was finding out that the aftermarket carb brass was causing me fouled spark plugs - a 12,500 ohm original spark plug cap also did not help.  With some no kidding OEM Honda Keihin brass / float assemblies and NGK spark plug caps, that smile has fully returned.

Rick

Gotta love that angry sewing machine!

[Don R]

 Just faaar idup an take off.

 The first 750 I got running after 25 years of no bike had a huge bog, I got mad and cranked it wide open, when it decided to go I was not ready and for 100 feet or so I was hanging on for dear life. I got a new respect for old 750's, drag strip launch, can't let off cause I'm hanging on for dear life, feet fell off the pegs, sliding back on a slick seat, yeow!

[BobbyR]

I think you may not have cleaned the accel pump completely which is why it bogged.

[ekpent]

 Do the 3,000mile tune-up stuff like plugs, valve and cam chain adjustment, make sure points and carbs are clean. Fogging the cylinders is a good idea when you first get one to lube while your doing these things. If you change the oil and filter a qt or so can be poured through the tappet covers to drain into pan. If your clutch is stuck keep it tied back to the handlebar and let the hot fresh oil do its thing. Starting for the first time off a slave tank is a good idea if you have one. When it does start monitor you oil light to go off and look inside the oil tank with a flashlight to make sure there is good circulation. Let it run for a short bit and check header pipes to make sure its firing on all 4.
  Good luck and hope it goes well.

[flybox1]

^^^this.
Post pictures of what you're working on! 

[BomberMann650]

And you're gonna need at least a six pack of beer for when you're done.  Or mostly done, or while reading the manual thinking how done you are with this sh!t.   

[Duanob]

After you get it fired up it may smoke a bit due to sticky rings but in my experience just ride the crap out if it, the harder the better, they will eventually unstick themselves.

[Kevin D]

Before you do any prelim blasts down the street, check your brakes, flush the 29 year old muck out of the system.
Fresh gas, fresh oil, new battery goes a long way.

[lockeed]

Thanks for all the info you guys provided.

As for the tank, it's spotless! Never seen a 40 year old tank so clean and shiny. The carbs, except for #1, they were very dirty and required almost 2 full days of labor to remove, dismantle, restore and re-install. What a pita to re-install these btw... That said, my 82 Nighthawk wasn't that much easier to reinstall... The 84 Nighthawk carbs are much easier to work with!

I'll need to order new boots for the air box to carbs, mine aren't sealing properly with the airbox. HOnnestly ,unless mine shrinkled over tiome, I don't realyl see how new ones would seat better on the air box... Do any of you have any issues with that?

I need to fix a leaking oil collant hose on the right side too. Speaking of hoses, the ones that are on there at the moment don't look stock to me. Can you tell me what type I should use or what the OEM were initially? I'll go grab some and replace them both.


Thanks again and on a side note, no chance for a blast down the street for me, there's about 6 feet of snow outside 

 

 

[PeWe]

Both chain tensioners will be like bakelite, not rubber. The upper wheel of cam chain tensioner will most likely leave small pieces of its hard rubber, especially during heavy decelerations. This will be visible in the oil pan and oil pump screen.

My engine got new tensioners winter 1983-84, years after engine rotated by kick 1-2 times/year.  Hard as bakelite when opened the engine 2010.

My CB750 was stored in cold barns during 19 years. Valve seats got pitted and in need of a fresh cut.

These old bikes need a complete engine tear down and restore due to its age, not because of use and ev. modifications as for 30-35 years ago.

[ekpent]

 I deleted my original post about the oil hose to engine leak because I did not notice you had an aftermarket oil cooler that you may be referring to about your leak. They are not a stock item for your bike so there is no stock hose per say. It could be eliminated if you wish or upgraded with better hoses and fittings if its leaking.

[Kevin D]

+1 on PeWe comments.

My own CB was parked for 15 years, 1987-2002, it got a kickover once a year and maybe one startup in that time. I was very reluctant to spend any serious money on it at its 2002 rebirth. I had more $ in new helmet, jacket, gloves than I did in oil, battery, tires, brakes. The compression was decent and it ran good so I rode it for a few seasons, 10000 miles?, before I opened the wallet. Maybe $1000 on the repaint (2006?) and $1000 in the engine (2007?), no performance parts just refresh, primary and camchains and tensioners, rings, gaskets/seals, lap valves.

[b1jackson]

Thanks for all the info you guys provided.


I'll need to order new boots for the air box to carbs, mine aren't sealing properly with the airbox. HOnnestly ,unless mine shrinkled over tiome, I don't realyl see how new ones would seat better on the air box... Do any of you have any issues with that?

I have some experience with this today in fact.. I had a set that I got with an airbox that I had soaking in wintergreen/alcohol for a week.  They were removed and shrunk back to size but still seemed fairly hard.  Perhaps my winter green was used up on the other boots I soaked.  When I put them on the carbs, the were very sloppy and no resistance at all to push them on.  Clamps wouldn't tighten enough either before bottoming out.

I have a new set of boots for another bike I have so I slid one on to try it.  Big difference. I can feel it more snug going on and it definelty  fit better on the carb.

[lockeed]

Quick update on the progress ad some questions for the pros. Today, it came back to life after a 30 year break. 

Started this morning by changing the oil. I replaced the oil cooler line that was leaking towards the bottom. Flushed the oil tank. Cleaned the gaz tank and petcock. Sprayed a tiny bit of WD-40 in the plug holes and put new plugs in.

Bike started up but I had to remove the choke and give it some throttle to come alive. It wasn't turning as it should. Oil light quickly switched off though. I let it rev at low rpm for about 10 seconds and shut it off.

Started to diagnose what could be wrong. I ended up cutting about 1/4" of my plug wires and reset them tight. A little fuel had come off from one of the drain screws on carb #4, so I worked the screw a little and it stopped. I ended up checking and resetting the other drain screw and found that carb #2 was barely dripping fuel when the screw was open. Telling me that the float needle was possibly stuck or something... I used a rubber hammer to knock on the carburetor a little... It probably worked as I was working on some other stuff, I finally got a good flow coming out of the drain spout on #2....

I restarted the bike, it felt much better, but still had problems idling. I was able to stabilise it at 2000rpm or so. Gong under that it would eventually die within 10 seconds. Keep in mind I'm still waiting on my carb sync gauges to arrive so that needs to be done. (side note, I bench sync them)

Couple things I noticed:

1) I barely had any exhaust fumes coming off from #2 cylinder/exhaust. I had more "air" coming out of the small drain hole than from the main exhaust hole... I ultimately found the culprit = looks like insulation from the exhaust... don't know how that could bundle up like that and clog the exhaust, maybe mice? Anyway, I took it off, so that's solved.


2) This is where I need you're help / Bike seems to rev on all four when you're past 4000rpm or so, but starting from a 2K idle, twisting the handle quick will make it sputter. It takes a second to rev, which makes me lean towards an accelerator pump issue... Maybe tied to or directly related to the stuck float needle and barely draining fuel issue noted earlier on carb #2...

also, like a dumda**, I just realised that the slow jets on the K7 are removable, somehow I had in my head that they were pressed in... Don't ask me why. They were cleaned and I ran plenty of comp;ressed air trough them, but I did not take them out. Could this be an issue as well? I'm attaching a picture of the plug on #2. Feels very dry to me. Note that the cylinder #2 also backfired a couple times under rev. 

Sorry for such a long ass text! I just don't want to mess anything up - I've been careful with the bike from the start... And learning a lot as I go. Never worked on this generation.

Thanks!

[MRieck]

Mice I'd say. 

[Mr. Mike]

If I remember correctly, your carbs are the same as mine...K8, and yes the slow jets are pressed in, but they will come out. I used pliers, pulling straight up with a slight twisting.
I would bet they're clogged. I use torch tip cleaners to get them cleared, blow 'em out and tap them gently back in until they seat.
 The accelerator pump is easy enough to check with the air box removed. Simply cracking (but not hard) the throttle, you should see gas spray (I mean spray) out of each of those tiny brass stand up nozzles. If not...the orifice may be clogged or the delivery tube between carb bodies may be the culprit, or indeed the pump itself is not working. Check that the pump needle (carb 2?) is just touching the depression tang on the carb linkage wheel when the throttle cable tension is zero..
I think you'd have done better by leaving the new plugs out, spraying in your choice of lube (I used Marvel Mystery Oil) and letting it set in the cylinders overnight, then kicking it over easy several times and let it sit again. Repeat the next day. Don't get to excited to hear it run, although I understand, just don't be in a hurry.
Once you've kicked it over a number of times (with a rag covering the plug holes) to clear out most of the lube stuff, then gap your plugs and install. Have a few sets available.
Cleaned carbs, with fresh gas and oil changed, new plugs gapped per spec, new fully charged battery, then see what happens.
You may yet need to find a early Honda mechanic to tune your bike, or you can glean from the forum and learn little by little and ride later and later. Either way, you'll appreciate what you have and slowly learn about it.
I don't claim to know a lot about these things, but my experience so far has been what I believe useful to pass on.
Keep us posted on your progress!

Sorry for the long a$$ed text as well.

[lockeed]

Thanks for the details Mike, I apreciate it.

One thing I left out, the wd40 in the cylinder did sat overnight - I hand crank the engine at first as well too. Still, tomorrow, the carbs are coming off again. Need to take a look at the slow jets and the accel pump. ...and the sticky float needle on #2. If it wasn't such a pain to remove and reinstall them...

[b52bombardier1]

My guess is that your slow jets will also have holes along the sides that will need to be cleaned - these are emulsion tube holes.

I think your carbs will also have a removable emulsion tube above the main jet. It's small tubes also need cleaning. I removed and reinstalled mine with a long golf tee which is a perfect material that is strong but softer than brass.

Rick

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