Topic: Just purchased a cb750 k has starting issues.

[walnut777]

Hello all. My name is Walt. Im new to the forum and new to street bikes. I just purchased my first bike. A 1977 cb750 k with 18k miles on it. I purchased it from a friend who could not get it started. It has some rust on the chrome, nice original paint on tank. Everything still original with a title for $400 bucks. I'm hoping it wasnt a bad investment. I jumped in head first b/c I have been wanting a street bike for a long time and the only way I can afford one is to buy a broke one and fix it myself.

here goes.

The plug wires are not spitting any spark.
I took the cover off and looked at the points. The point that is closer to the back of the back has a blue spark while the other point has no spark. The points and all are brand new.
There is a green wire  that goes onto the bolt that holds the ignition coil to the frame. Is it suppose to have power? If I disconnect it the lights on my gauges go off. It has 12 volts when hooked to a multi meter.

I read a post earlier of a guy on here who has a cb750 and his starting problem was in his kill switch. I will try that method tomorrow.



Also, my front right side turn signal stays on all the time. It will blink if you turn the signal on but when the signal is off the lights stays lit. Any ideas what causes this?

The headlight switch will make the headlight bright and normal as is should but if you press down on it a little the headlight will go off? Is this anything to worry about?
Thanks in advance for your help.

[HondaMan]

The Green wire at the coils is the main ground wire for the frame. Make sure it is well connected to cleaned bolt surfaces, so the frame gets grounded.
This wire connects (eventually) with the (-) terminal of the battery. Make sure the big cable from that same terminal has a clean connection at the engine,
which should be at the top left rear mount of the engine, between the engine and frame, on a big bolt that also holds the engine.

It sounds like the ground wire for that turn signal might be loose, so look inside the headlight bucket for that.
Those front yellow lamps have one filament for "running lights" that come on with the headlight, and another filament for the turn signal.
Some of those turn signal stalks have a 3rd Green ground wire that goes into the headlight: some don't, but have a connection to the stalk
where it bolts to the headlight or fork ear.

At the coils, make sure the Blue and Yellow wires are plugged into good, clean connections with the coils. Those 2 wires go to the top
right rear of the engine, near the oil tank, and plug into another 2 wires (also Blue and Yellow) that continue on to the points. The left points
set is labelled for "1-4" on a Blue wire, which is the coil for cylinders 1 and 4. The other points set is for 2-3, on a Yellow wire. If the points
do not have 12 volts on them when they are open, they might be mis-connected with the little wires that bolt onto the points, so check that.
If the wire touches the frame of the points, it will ground it out and no spark is possible. When the points are closed, they ground the (-) side of
that coil (either a Blue or Yellow wire circuit) to charge the coil: when the points open the coil collapses and makes a spark.

The "kill switch" provides power from a Black wire in the headlight, up to the Run-Off switch on the right handlebar (that's the 'kill' switch),
where it becomes a Black/White wire that goes back through the headlight and then to the coils. This is the power to the coils. You will see it
connected to the coils near that Green wire you were mentioning: make sure the +12 volts appears on that Black-White wire, or follow this path
I just described to find out where is might be missing.

That should get the basics... 

[Spanner 1]

You could have several issues Walt !......... however, with the ign. on and each point open ( slide a piece of card between the points to be sure they are open ) you must have battery voltage on the blue and yellow wires at each point. If not then look at the connection at the point , that there is no short to ground ( points plate ). Trace the blue/yellow where it comes out below the points and follow it to the connection above the brake light switch, all o.k. there ? I should have said first, are the points shiny as any corrosion 'film' will stop that spark ? Don't answer 'Yes' unless you have cleaned/shone the points today  ........ some stuff to check.

[Trav-i]

Walt, 

Your turn signals sound like they're working right.  The big signals you have are like mine, in 75 or 76 Honda started using the Goldwing signals for just about evrything.  The front signals are also running lights the bulb number is 1157.  The rear signals are still just sginals only, no running lights.

[Elan]

Well I cant add to the great tips you already got, but I will add that you got an awesome deal! upload some pics soon