78 cb750K - Getting it going

[NorthernD]

I bought this last year for $600, pretty good deal as I was told it ran but had sat for two years.


I have so far replaced the oil, oil filter, and cleaned the air filter. I have also replaced the spark plugs on this as well.
At this point I could only get it to run with the choke on. It would not idle.
I have recently taken the carbs apart and cleaned them out cleaning the jets and bowls it did not look too bad except for one clogged jet. I put it back together and actually got it to run.
At first it took a while to get it to idle and now idles fairly high but is running super hot and hissing a bit. I am going to take them off again as I now need to take out and clean the idle jets. Hopefully that gets it running a little better.

I am pretty stoked to have it at least moving and am looking forward to doing a little more. Any advice is welcome.

I will post again as the pictures do not seem to be loading

[TOOLS1]

It looks like you have the 77-78 keyhole carbs on it. The pilot jets are pressed in on those carbs. I have a tutorial in the repair section on how to make a little puller, and safely remove them. It also sounds like you have a very lean condition. I drill out the pilot jets to .45mm this helps out a lot with the lean condition, and cold starting.
http://honda-cb750-s.456789.n3.nabble.com/Removing-pressed-in-Pilot-Jets-from-Keyhole-carbs-td4036674.html
TOOLS

[Hoosier Daddy]

NorthernD wrote

 now idles fairly high but is running super hot and hissing a bit. I am going to take them off again...

"hissing a bit" ? Depending on what that means your symptoms sound like a vacuum leak. Check the mounting and integrity of the rubber insulators (boots), make sure you don't have a way for unmetered air to enter the intake.

[NorthernD]

I will be looking into this could be the issue. It also seems that the exhaust may be the problem as it does not appear to be mounted correctly either (missing a nut) so I am thinking that could be an issue.

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Date: Sat, 22 Jun 2013 02:55:18 -0700
From: [hidden email]
To: [hidden email]
Subject: Re: 78 cb750K - Getting it going

NorthernD wrote

 now idles fairly high but is running super hot and hissing a bit. I am going to take them off again...

"hissing a bit" ? Depending on what that means your symptoms sound like a vacuum leak. Check the mounting and integrity of the rubber insulators (boots), make sure you don't have a way for unmetered air to enter the intake.

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[NorthernD]

Cool I will look up the tutorial. I used taped pliers wrapped in a t-shirt and managed to get them out, as I said looked pretty good for the most part and now seem to be working. I will run it again hopefully today and should know more then.

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Date: Fri, 21 Jun 2013 22:23:43 -0700
From: [hidden email]
To: [hidden email]
Subject: Re: 78 cb750K - Getting it going

It looks like you have the 77-78 keyhole carbs on it. The pilot jets are pressed in on those carbs. I have a tutorial in the repair section on how to make a little puller, and safely remove them. It also sounds like you have a very lean condition. I drill out the pilot jets to .45mm this helps out a lot with the lean condition, and cold starting.
TOOLS

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[sgtslag]

SeaFoam will remove minor varnish deposits in the fuel system...  I add it around once per month in the riding season, to absorb water, dissolve varnish build-up, and to just keep it running smoothly.  I also top off the fuel tank with gas, then add the correct amount of SeaFoam to the fuel, for Winter storage.  Bike runs great, come Spring!  Will preserve gasoline for up to 12 months, after that, it turns to varnishy goo.


It can also be added to the crankcase oil:  dissolves varnish, carbon deposits, absorbs water, and just plain cleans out transmission, as well as the engine.  After adding it (directions on the can), run the engine for five minutes (either a short trip, or run it on the center stand, shifting through all five gears, idling.  This will thoroughly flush out the entire engine, as well as the transmission.  Then change both the filter, and the oil, which will likely have turned coal black with deposits.  You won't need to do this flush again, for 20,000-50,000 miles, if using modern SM oils; if you use type SF, or something of that vintage, it will leave deposits and sludge in the engine/transmission much sooner.  Cheers!