Topic: the 1-4 coil mystery??

[bollingball]

SAW you keep saying 1&4 and 3&4 is it not 1&4 and 2&3 maybe mines different?

[bollingball]

One time you said 3&5

[bollingball]

Not trying to be a ahole really just trying to make sure of the the problem cylinders

[saw750]

speaking of human error - thank you for your patience lol

a decimal point makes a big difference...so much so i fixed my original answer..lol

1-4 POINT OPEN 10.7 VOLTS

1-4 POINT CLOSED 1.2 VOLTS

GROUND SIDE OF POINT TO BACKING PLATE .5 OHMS

(bollingball thank you for pointing out my typos there is no excuse. tired eyes and i cant type. i have gone back and corrected the errors. 1-4 bad. 2-3 good)

[CB750F2]

That's better Saw. I would remove 1-4 points clean and remount and remeasure the resistance - easy to do. The 0.5 ohm reading that you measured may account for the 1.2 volts that you got with the points closed. I suggest that you also measure the resistance between the backing plate and engine casing and while you are at it measure the resistance between the engine casing and the large negative battery lead. There should be little or no resistance. If it was my bike I would be testing both condensors and replace with new ones if they were doubtful. I say this because the bike has been standing for so long and condensors deteriorate over time. I would probably replace the points as well. Anyway please continue with the way that you are going. I also need to talk to you about the starter push button. As long as you still have the lighting fuses removed there is no issue so lets leave that until we get th espark issue sorted. Pat

[saw750]

backing plate and case: .4 ohms

negative battery cable and case: .4 ohms

cleaning etc will have to wait until tomorrow. i do not have another set of points. i will have to check the local honda dealer

[CB750F2]

Ok. I need to do other things as well. I don't know what type of meter you are using to measure resistance but it can be a difficult to interpret low resistance readings. You need to first take a reading with the instrument leads shorted together and note this reading. Take a reading across the points of interest. The resistance across the points of interest is then the difference of the two readings.
Ok, now I will explain the starter push button issue. You said in one of your early posts that you purchased a push button with two sets of contacts and indicated that both sets of contacts were open when the button was not pressed. This is not what is needed. You need one set to open and one set to be closed. A black and a black/red wire should be connected across the closed contact and a black and a yellow/red wire should be connected across the open contact. This arrangement will ensure that there is no electrical load due to lighting when cranking the motor via the starter motor. This is not an issue at the moment because you have the light fuses removed but you will have to fix this at some stage. Pat

[saw750]

i do have a another switch.

SPDT Center Off High-Current Mini Toggle Switch
http://www.radioshack.com/product/index.jsp?productId=2062486

[CB750F2]

Saw, yes you need a SPDT push button but not a SPDT centre off toggle switch. The black wire goes to the common terminal of the switch, the bk/r wire goes to the normally closed terminal - that is the terminal that has continuity with the common terminal when the push button is not pressed - and the y/r wire goes to the normally open terminal. So, let's assume that you are ready to start the bike. The ignition switch is ON, the bike is in neutral and the kill switch is selected RUN but you have left your head light on. As soon as you press the start button the normally closed contacts will open switching the head light off - this removes any unnecessary load off the black wire- and the normally open contacts will close allowing power to the starter solenoid. Anyway fix your spark problem first. Pat

[Spanner 1]

Wait now twice you have reported voltage on the 1-4 points with the points CLOSED = wrong.
Post #34...." voltage on blue wire ( 1-4 points ), 10.7v WITH POINTS CLOSED."... and post #51
... "1-4 POINTS CLOSED = 1.2v....... O.K... if your points are actually closed and making contact with each other then voltage on blue wire ( or yellow wire ) = 0 volts ( zero ).... nothing else.... there must be some misconception here about how the ignition works ?..... with a clearly visible gap in the points, the voltage on the blue ( or yellow) wire will be a little less than battery voltage.... with the points closed this voltage MUST drop to 0 volts, otherwise your points are not closing or badly corroded ( not in this case) What's the point gap, please ?

[CB750F2]

Hello Spanner. Yes Saw reported that he had almost full battery volts with the points closed. I pointed this out to him and he has corrected his mistake. He now reports 1.2volts. Yes it should be zero volts if the points are clean but he also reports some resistance between the ground side of the points and the backing plate so it all depends where he is measuring the volts - across the points or across the points and the junction of the backing plate and the ground side of the points. Anyway I have asked him to remove the points for cleaning - see my posts. Pat

[saw750]

my skills with a multimeter have always been as questionable as the multimeter itself lol..so i do appreciate the patience..

i retook the resistance readings at the plate to the block and the negative mattery to the block..each were 0 to .1 ohms...when this is done i will sleeping with this ohm meter underneath my pillow..lol i am getting better

am cleaning the points today...i havent found the camera yet but i can tell you that the everything isthat the igintion plate and components are in remarkably good condition..ie free from visible oxidation or dirt etc..its very clean...

[saw750]

annnnnnnddddd the winner is a new condenser or combination of new condenser and clean points

i scavenged the local shops for parts and i did manage to find one condenser...i cleaned the points again and reinstalled and there was no change..installed the condenser and i had park on all four plugs

i did order new points and a another new condenser

thanks to everyone for their patience and help (a special thanks to Pat for the extra help)

now about that switch lol...where would if ind such a thing lol

[TwoTired]

annnnnnnddddd the winner is a new condenser or combination of new condenser and clean points

i scavenged the local shops for parts and i did manage to find one condenser...i cleaned the points again and reinstalled and there was no change..installed the condenser and i had park on all four plugs

i did order new points and a another new condenser

There are some other possibilities.
The condenser for the 1-4 may be leaky, and this effects the voltage input to the coils and how briskly they can fire the spark plugs.
Further, point contact deterioration may be adding resistance to the 1-4 primary circuit, which in turn, effects how much spark voltage can be developed by the coil for the existing spark gap.

Lastly, when was the last routine 3000 mile tuneup done to the bike?

Cheers,

[saw750]

yes thank you. you were correct

[Spanner 1]

Great... glad the bikes firing on all 4 ... now you will set the point gaps and time the bike, right , just to complete the project.......

[CB750F2]

Saw, it is great to see that you have solved your problem. You have probably learnt a lot in the process. You are now in a much better position to fix similar problems. To fix something you need to understand the workings of the system/process that is giving you trouble then use a combination of reasoning and measurement to pinpoint the cause.
The push button. Is it possible to repair the original? You could try your Honda dealer or a motorcycle wrecker. I would try those options because then you don't have the problem of mounting a non-OEM switch. A non-OEM P/B should be readily available at most auto stores. They may have four terminals two for the normally closed and two for the normally open contacts. In this case you would have to bridge two of the terminals-one from each set-to form a common. There is another option. Use a P/B with one normally open set of contacts and connect a black and  y/r wires to these so that power is supplied to the starter when the P/B is pressed. The b/r wire can then be joined to the black. You will then need to remember to turn the head light OFF before starting the bike. Pat

[saw750]

Yes thank you Pat..I learned much. And sometimes the best possible way to learn is by making mistakes along the way...thank you again for your patience.

Pushbutton. No it cannot be repaired. I was in the process of installing new throttle cable, opened the right hand switch and the button disintegrated - the plastic was brittle and cracked.

One of the issues with any switch is "physical size". I wanted a switch that fit in the switch housing and mimicked the appearance of stock.

Your second option: I think that is what I have now? but with black and black/red joined at one post

i have a normally open push button switch - with two posts - to one post is black and black/red - this powers the lights and the lights are always on.

the red/yellow is connected to the other post - when the button is pushed power is supplied to the starter.

the flaw in this system...is that the lights are always on even with starting...

i must not be reading/visualizing your second option correctly?

maybe this?

http://www.radioshack.com/product/index.jsp?productId=2062541

what i would need is a pushbutton SPCO switch?

[Jim F]

I had a problem with 2/3 not firing
checked everything with a volt meter
coils good, ignition box good, everything checked out but no spark

 It was a Bad connection

Just damn

The beast runs

Jim

[bollingball]

Saw you can still get the black button,spring and contact plunger from (partsnmore.com) take a look that was all I needed.

[CB750F2]

Saw, you have interpreted the second option correctly but I may have given you incorrect information about the lights. I have assumed that you had an additional light switch to control your lights. My bike is a 78F2 and it has a separate light switch as well as a dimmer switch. So if you do not have this switch on your model the second option is not for you. Bollingball has given you the best option - put it back to standard. Pat

[saw750]

bollingballs option is not applicable since  the switch internals were garbage.

ie the plastic housing containing the spring etc was in numerous pieces, cracked, brittle etc etc

the only thing salvageable was a cracked switch plate with three soldered wires....

[CB750F2]

Ok, if you cannot buy new parts then try ebay. Search using "CB750" and see what happens. I see handle bar controls for auction sometimes. Another option is to try a wrecker. Pat

[Frostyboy]

http://www.davidsilverspares.co.uk/CB750K6-FOUR-1976/part_105330/