1980 Honda CB750F (The Honey Badger) Bobber Project

[Redemption]

Hi there Im working on finishing up a bobber conversion and one of the major tasks to handle is the wiring. Luckily there is most or all of a wiring harness and it was even labeled  so this really couldnt get any easier but before I start hooking power up to everything ive plugged in I want to double check for any tips or hints so I dont go and do something stupid and costly like blow the cdi box

[shinyribs]

DOHC hardtail! Very cool! Welcome to the forum. Download the factory service manual for your bike at the top of the page,it may come in handy. Looks good!

[Redemption]

Ok so I ran a test and mocked up all the wiring. Engine is turning etc fuses not popping but Im not getting any spark at the plugs.

bad coil? bad cdi? bad rectifier?

[TOOLS1]

Cool bike!! You can test the coils with an ohm meter. They should have continuity between both spark plug wires, and between the + and - terminals. Sorry I am not more familiar with the DOHC bikes, however there are some here that are, and I am sure they will chime in.
TOOLS

[Redemption]

Tools, you sort of lost me there, sort of but not all the way. That is the next step I suppose. I am sorely tempted to drop the wiring harness completely and wire it up from scratch.

In this instance I have 3 or 4 plugs that dont go to anything. Likely for the tach/speedo and likely for the start stop switch which I dont have. Should I mock up a toggle someplace to simulate the secondary switch? (handlebar start stop switch)

Sohc would be a lot easier but I got a fantastic deal on this dohc set up.

I know the two ignition coils go out a lot but my understanding is that they do not often both go out so I cant help but wonder if I am missing something here thats causing a break in the circuit and not sending a spark to the plugs.

[TOOLS1]

I always prefer to wire my custom bikes from scratch. The procedure, for testing the coils is in the manual. You can download it from the top of the forum lists from the manual thread. If, you have 12 volts going to the + on the coils, it should run.
TOOLS

[Redemption]

Im about to head out the door but I was scanning the manual lists and I dont see anything coil specific, which manual should I be downloading?

Thanks by the way for your compliments. It is a sexy bike and I hope it rides ok for a rigid. I figure one in this kind of shape deserves a clean wiring job. I was hoping for everything to be simple on this but of course as is usually the case with these sort of deals, diagnosing the problem is always part of the game.

[TOOLS1]

Just download the manual, for the year bike, you have. The coil testing procedure should be in the ignition section.
TOOLS

[Redemption]

Downloaded the manual today and its become clear to me the engine will crank with the start stop switch off, it just wont start. Im going to test that first. then otherwise I suppose it will be time for more advanced testing...

Im a bit of a knuckle head when it comes to wiring so this is going to be slow going for me.

from the manual:

Engine cranks but will not start
-engine stop switch OFF
-No spark at plugs
-faulty transistorized spark unit
-faulty pulser generator

No Spark at plug
-engine stop switch OFF
-poorly connected broken or shorted wires
-faulty ignition coil
-faulty ignition switch
-faulty spark unit
-faulty pulser generator

I have no switch in the loop period so I have to figure out where that goes.

[Piute]

                                                                   
                                        Trying to be cool about how to hot wire a 750
 
                                                                 
                                                             I no nothing

[Redemption]

do we have a wiring guru of any sort here who can step me through this?

[TOOLS1]

This sounds like a job, for the Sarg. If it were a SOHC with points, I could do it blindfolded. However I have never done a DOHC.
TOOLS

[Redemption]

who is sarge?

[shinyribs]

Redemption wrote

who is sarge?

Sarge goes by the name SgtSlag on here. Ooh Saaaarge...where are you Sarge??

[Redemption]

yeah I would love his help.

BTW as per the diagram for this particular bike

1980 cb750f   http://www.oregonmotorcycleparts.com/Diagrams/CB750F_dohc.jpg

I jumped the black wire to constant power hoping that would give me some spark. if I read the diagram right it should. no spark no change. Motor cranks no spark at the plugs

[Redemption]

Ok sorry let me make a correction the black wire and the black and white wire from the same plug need to be jumped together however that is not my problem.

I would just about be ready to bet the farm that the ignition coils are my issue. Their both splitting on the bottom. that part cant be good.

[TOOLS1]

Did, you find the part in the manual about testing them? It should show taking a reading across the two plug wires with an ohm meter, and then across the two small wire connectors. You should have continuity across both.
TOOLS

[Redemption]

I just ran a quick test with the voltage meter set to ohms 200 and tested as shown in the picture below (red circle red test lead black circle black test read) the result was 3.5 ohms the internetz says 3.0 is proper.



When I reverse the leads from what is shown in the picture there I get wonky ever shifing readings.

When I try to get a reading at the spark side of things caps on or off I get a 1 on the ohms reading which is what it reads when its touching nothing.

Thoughts? is my ignition coils fried?

[TOOLS1]

You tested the +, and - terminals correctly. Just to clarify on the plug wires. Red lead on one wire, and black lead on the other wire. It should read 0-1 meaning it has continuity. Another thing to do is to test, for 12 volts going through the two small terminals. I had one go bad once. It was only letting 7 volts go through.
TOOLS

[TOOLS1]

I found this, for, you. Hope it helps.
TOOLS